VMWare Interview Questions and Answers

What is Hypervisor?

Hypervisor is also knows as Virtual Machine Monitor/Manager (VMM) is computer hardware platform virtualization software that allows several operating systems to share a single hardware host. 
Each operating system appears to have the host’s processor, memory, and resources to it. Instead, the hypervisor is controlling the host processor and resources, distributing what is needed to each operating system in turn and ensuring that the guest operating systems/virtual machines are unable to disrupt each other.

What is VMware ESX/ESXi?

VMware is industry leading virtualization software. ESX/ESXi installs a hypervisor on the hardware. It acts as the intermediary between the hardware and any virtual machines running on the server. Hardware device drivers are included in the hypervisor. This is called a direct driver model.

What is Hyper-V?

Hyper-V also installs on bare metal. But all management functions and access to hardware is controlled via a “root partition” that runs the Windows Server (or Server Core) 2008 OS. This root partition is actually a special virtual machine, through which hardware I/O requests from child partitions travel via the VMBus architecture. This is called an indirect driver model. So basically before you enable the Hyper-V role, your server OS is of the typical architecture, after enabling the role, Hyper-V installs itself on top of the hardware, and places your original OS into this special virtual machine, the root partition.

What is the difference between VMware and Hyper-V?

A comparison of certain key features between platforms:

1)    ESX supports both 32 & 64-bit hosts, Hyper-V requires a 64-bit host that supports hardware-assisted virtualization. All platforms support 32 or 64-bit guests.

2)    Maximum Logical Host CPU’s: ESX = 32, Hyper-V = 16 (can do more, but not supported)

3)    Maximum Supported Host Memory: ESX = 256 GB, Hyper-V = 2 TB (2008 Enterprise Ed.)

4)    Maximum Memory per Guest OS (VM): ESX & Hyper-V = 64 GB

5)    Maximum Supported Running VM’s: ESX = 128, Hyper-V = limited only by available resources

6)    RAM Over-Commitment: Supported in ESX, not supported in Hyper-V. (This allows RAM allocated to VM’s to exceed actual available RAM in host).

7)    NIC Teaming: Native support in ESX. Hyper-V only supports via 3rd party drivers.

8)    Maximum # Virtual Switches: ESX = 248, Hyper-V = unlimited

What is VMware Library?

VMware Library is known as /vmlib. It is a directory on the ESX hypervisor host. It contains the files to organize the tools and files that require maintaining and managing the virtual Infrastructure.

I can't add a new virtual hard drive to my virtual machine. What should I do?

This could be with the following reasons

1)    You may not have appropriate permissions to add new hardware to the virtual machine and

2)    VM might be in powered on state.

I just created a new virtual machine and attached to an existing disk. Every time I power on the VM, I get a blue screen. What could the problem be?

It could be the insufficient or unmatched configuration of a new virtual machine against to existing disk configuration files. The reason is existing disk configuration might be different than the new virtual machine. Compare the settings like as “Storage controller, hardware properties etc.”, make the changes accordingly and try powering it on the machine.

Active Directory Authentication Fails when logging into host or vcenter server using Domain Credentials

Check the time on the esx host and on domain controller. The issue could be with the following reasons.

1)    Time synchronization issue from esx hosts to domain controllers. Kindly review the system logs.

2)Network Latency Issue

How to troubleshoot PSOD Issue in ESX?

PSOD is known as Purple Screen of Death like as in windows BSOD- Blue Screen of Death.

PSOD occurs due to the following reasons

1)    Bad Drivers

2)    Incompatible Drivers

3)    Hardware Faults

4)    Kernel Corruption

5)    Application Corruption

How to export logs when PSOD occurs in the ESX host

You can export the logs either from vcenter using VI client or generating logs on root directory in the host using commands.

1)    Exporting Logs using VI client

Connect to Vcenter server using VI client and select the crashed host then Click file (on the top-left side corner)>export>system logs> give the temporary location path> click start. After couple of minutes logs will be exported to temporary location

2)    Connect to host in # prompt, type “vm-support” without any options. This utility will create and saves the crash dump by default on /root directory in .tar.gz format.

What are the reasons for “Failed to load, swap file not found” error

The Reason can be:

1.     Lock was not free

2.     Invalid metadata

3.     Not found

4.     Busy

5.     IO was aborted

6.     Permission denied

7.     No connection

8.     Not supported

How to troubleshoot “failed to load, swap file not found” error

Refer the KB article: http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2013834

What ports does P2V uses

1.     From Source Computer to ESX uses for communication are TCP Ports 443,902

2.     From Converter server & client to Source Computer are TCP ports 445, 9089 or 9090,139 and UDP ports are 137, 138

Question #1 (Whiteboard & Marker Required)

Please draw on the whiteboard a high level drawing that details a cluster of 4 ESXi hosts, connected to a vCenter, that has 20 VMs evenly balanced across the hosts. There are 2 network switches (A & B) connected to vSwitches for data and management vLans. The hosts are connected to 4-500GB shared storage LUNs that are presented via fiber channel.

Note: Most qualified virtualization engineers will be able to draw something. If you are recruiting to fill an engineering spot that will be representing your team, it is important that they can whiteboard a high level design with confidence.

Question #2

Explain the process of P2V and the cleanup process that is required after Windows Servers have been converted from a physical server into a VM.

Answers: Uninstall all no longer required applications for physical hardware, remove hidden devices, and adjust drive sizes, memory and vCPUs. Install VMtools and set screen resolution. Adjust OS swap file.

Question #3

A new type of SAN storage has been added to the environment to replace the old SAN storage. After presenting the new datastores and migrating the VMs to them, users report slower performance. What could need to be done to the VM file system to fix this?

Answer: Run a block alignment which requires a reboot of the VM (this may not be required on newer operating systems).

Question #4

You have a cluster of 8 ESXi hosts that require installation of a new security patch that will require a reboot of each host. Explain how you would reboot each host without impacting the VMs.

Answer: Place each host in maintenance mode, which will automatically vMotion the VMs off, then install the patch and reboot the host. Once all is okay and the host is back online, then remove the host from maintenance mode. Repeat the process on the other 7 hosts.

Question #5

Describe how you would determine when additional ESXi hosts are required? Explain how you determined this?

Answer: By setting thresholds and monitoring host memory and CPU utilization.

Question #6

How many ESXi hosts have you been responsible for managing in the last 3 years? Ask about the challenges faced.

Answer: More than 30 ESXi hosts is best to provide them with enough hands-on time to experience most of the common issues associated with virtual infrastructures. ESXi Updates, storage, VMtools are common problems.

Question #7

How many P2Vs have you completed in the last 3 years? Ask about the issues they had.

Answer: More than 25 P2Vs is best because each P2V is unique and develops knowledge of workarounds important for future consolidation projects.

Question #8

How many VM gold templates have you created? Explain the process you used for resetting any 3rd party applications such as antivirus and backup agents, or any other application which requires a unique key.

Answer: Windows GUIDs are unique IDs that need to be reset or they will be duplicated and cause issues. Also, it is important to sysprep each Windows Server created.

Question #9

Do you have any experience with cloud automation scripting that leverages Amazon AWS or other cloud computing provider APIs?

Note: Any experience in this area will be beneficial to longer term growth of your environment.

Question #10

What are your recommendations for backing up VMs? Follow up question, what are your recommendations for monitoring?

Note: These VMware technical interview questions will help you determine what 3rd party applications they are familiar with and allow the candidate to show you if they are passionate about the technology.

Conclusion:

If your interviewee can't answer these questions with a conclusive answer then they probably don't have much experience outside basic setup and installation training.

 Q: How is VMware more stable than, say, a new physical server?

A: The idealized hardware provided by VMware provides a consistent virtual hardware environment that increases that stability of your virtual machines independent of the underlying physical hardware.


Q: Is any installation method better than any other?

A: No. Whichever installation method you're comfortable with and that produces a good build is the one for you.

Q: I'm having problems with my installation. What should I do?

A: Ensure that the hardware you're loading ESX Server on is supported. The same goes for the configuration. If you are certain the hardware and configuration are supported, then run the vm-support script mentioned previously.

Q: Why does this chapter include only the graphical installer method?

A: It's the recommended installation method from VMware and one that many in the x86-world are the most comfortable with. If you wish to try it another way, VMware offers a very complete installation document covering the various installation methodologies.
Q: When I copy my virtual machine and try to run it on my network, I get hostname already exists and IP address already exists errors. I thought I could simply copy my virtual machine. What is the problem?

A: You can copy your virtual machine, which is why you're running into this problem. The copy is an exact copy. Thus, you need to change the hostname, IP address, and even the computer's SID (if it has one).

Q: Can I move my Gold Master to my other ESX Servers?

A: Yes, it's a recommended time-saver. If your ESX Servers share a LUN, that too is a way to access your Gold Master or your VMlibrary for that matter.

Q: Are there any limitations to the number of virtual machines I can run on my ESX Server?

A: Yes. Each ESX Server allows for only 80 virtual CPUs and 200 registered virtual machines.

Q: Can I take a virtual machine running on VMware Workstation or GSX and run it in ESX?

A: It depends. The process is not as simple as cutting and pasting. There is a specific import process required for migrating virtual machines from either Workstation or GSX into ESX. Access the following link for the exact instructions: http://www.vmware.com/pdf/mobility_guide.pdf.
Q: Do you need to tweak the settings of your virtual machines after you've built them?

A: No. VMware has configured the defaults of your build to suit most server loads. However, depending on the profile of your server and the resource intensiveness of the service it's providing, you may want to consider tweaking some of the default settings to better ensure service stability and reliability.

Q: Are there more advanced features than the ones detailed in this chapter?

A: Yes… a lot more.

Q: Is clustering more stable in VMware?

A: We find that the idealized hardware, in combination with VMware's improvements in clustering support, has made virtual clustering very stable.

Q: Can you Vmotion a cluster?

A: That depends on the cluster type and how it is configured. Clusters using Raw Device Mapping in virtual mode can be moved with Vmotion according to VMware documentation.
Q: Does VMware support NIC teaming?

A: Yes, and it's a very good idea to configure your ESX Server, especially if it's for production, with teamed NICs. This will provide hardware fault tolerance in case one NIC fails.

Q: How many physical NICs do I need on my ESX Server?

A: That depends on the number of virtual machines and the network traffic they produce. You should have a minimum of two: one for your Service Console and one dedicated to your virtual machines.

Q: If I'm building a cluster using Microsoft Clustering Service, what's the best configuration for my heartbeat NIC?

A:For a Cluster in a Box, create a VMnet that your nodes of your cluster can attach their heartbeat NICs.

Q: Can you attach virtual machines on any ESX Server to a VMnet?

A: No. Only virtual machines on the ESX Server that the VMnet resides can attach to it.
Q: Why should you pay for a p-to-v toll when there are a number of ways to do it for free?

A: If you don't have the time or inclination to learn the manual process or need the assurance of a vendor for your physical-to-virtual migrations, then a tool that comes with support is a very reasonable option.

Q: What takes the longest in the p-to-v process?

A: Transferring the data of the physical server into either an image file or the virtual server itself. That's why tweaking your network settings for optimal throughput is essential when p-to-v'ing a server.

Q: Can you create complete backups of your physical servers and then recover them into virtuals?

A: I've used NTBackup to back up Windows 2000 Professional and Windows XP, and created virtuals out of .bkf files. It works but there's a bit of futzing around with the virtual once it is running. Try it.

Q: What's the most essential part of creating a smooth migration plan?

A: Practice. No matter what the tool or process, practice it and learn its gotchas and the workarounds. No matter what method you use, there will be times when it won't go as planned. Practicing your p-to-v process on a number of physical platforms and disk configurations allows you to become more adept once you're doing it for real.
Q: Will my software vendor support my application in a VMware environment?

A: You'll need to contact your specific software or applications vendor to find out; however, an increasing number of software vendors support virtualized environments. Once you've migrated your application from a physical to virtual environment it's very easy to migrate back to a physical environment for vendor support. An excellent document provided by VMware can be found at the following link: www.vmware.com/pdf/ms_support_statement.pdf.

Q: What are the best enablers to help ensure our server consolidation is a success?

A: Engaging with the lines of business and application owners not only assists in attaining an actionable schedule, but also develops a highly collaborative environment that facilitates buy-in and support for your project. In addition it will be difficult to incorporate rationalization into your project unless you are working directly with the business or application owners.

Q: What tools do you recommend for a server consolidation or virtualization project?

A: It's imperative to have a robust and comprehensive tool for capacity planning, including historical data. This tool can be utilized in every phase of your project. Other tools to support the project include modeling tools used in test consolidation scenarios. Finally, you'll need to evaluate and document tools and processes for each technology you wish to consolidate. The migration tools will need to support all the platforms you wish to use in your migration scenarios.
Q: What is the VMlibrary?

A: The VMlibrary (/vmlib) is simply a directory on your ESX Server that lets you organize the tools and files you need to manage and maintain your virtual infrastructure,

Q: Can ISOs be shared between ESX Servers?

A: If you place your VMlibrary on a LUN that's shared amongst your ESX Servers, you can share your ISO images or anything else you place in your VMlibrary.

Q: Why is Vmotion so cool?

A: Try it…and then imagine the possibilities and applications. You'll be a convert soon enough.

Q: You mentioned that additional ISVs were creating management capabilities for virtual infrastructures in their products. Which ones?

A: Look at HP Insight Manager, Dell OpenManage, IBM Director, BMC's Patrol product line, Computer Associates' Unicenter, and many others.
Q: I can't add a new virtual hard drive to my virtual machine. What should I do?

A: You may not have the appropriate permissions to add virtual hardware to the VM, or the VM may be powered on and won't allow the addition of virtual hardware while powered on.

Q: I just created a new virtual machine and attached to an existing disk. Every time I power on the VM, I get a blue screen. What could the problem be?

A: Make sure the OS type that you selected when you created the VM matches the OS type installed on the virtual disk. For example, if you selected Windows 2003 Standard for the VM when you created it, but the existing virtual disk has Windows 2000 Standard installed, you'll probably encounter issues.

Q: I followed the directions for Active Directory authentication, and I still can't log in using an account and password in AD. What should I do?

A: Check the time on your ESX Server and Active Directory and make sure they're synced up. Kerberos is very sensitive to being out of sync and could reject credentials if the time is not within specific limits. You can also review the System event logs for clues.
Q: What is the most important aspect of deploying ESX Server and virtual machines?

A: The ability to provide service at least as good as that which you had with physical servers. With adherence to best practices, you should easily be able to provide this and exceed it by a phenomenal degree.

Q: ISOs have been mentioned in several of the chapters. Why are they so important?

A: Good administrators strive to never leave their chairs, cubes, or offices. If they do, they may just run into a user (we're kidding, of course). Having a library of ISOs can help you in this endeavor. In addition, they run a lot faster than regular CDs.

Q: What will happen if I deploy systems management software on the ESX Server itself?

A: If you're going to do this, make sure you allocate enough memory so that the application doesn't impact the performance of your ESX Server and thus your virtual machines. Also, use a system management package that is supported and test your installation on your ESX Server thoroughly. If you notice a degradation of performance, contact the systems management software vendor. The major vendors have instructions and best practices for deploying their products onto ESX Server.

Q: What is the most important best practice to follow?

A: The one that ensures your smooth evolution into a virtual infrastructure education. Learn every aspect of a virtual environment to the best of your ability. Be passionate about it and you'll reap the rewards. See the recommended reading list, troll the VMware Web site regularly, as well as other Web sites dedicated to virtualization such as p2v.net, vmguru.com, and virtual-strategy.com.
Q: Which version of VMware ESX Server supports Boot from SAN?

A: ESX Server 2.5 supports Boot from SAN but has the following limitations: ESX server had to be installed in boot from SAN mode, the HBA can only be used by the Service Console, LUN masking should be used to restrict other ESX servers from the boot LUN, the HBA of the boot LUN must be a QLogic HBA, and the boot LUN must be the lowest numbered LUN controlled by the storage processor.

Q: Where are log files for VMware ESX Server written to?

A: /var/logs/vmware

Q: What do you do if you forget the root password of the Service Console?

A: You will need to boot into single-user mode from the Service Console by selecting linux from the LILO boot menu and appending -s to your boot choice. This will boot the console into single-user mode and will allow you to use the passwd command to change the root user password.

Q: Why do I still see processes for my virtual machine when running the ps command on the Service Console even though my virtual machine is powered down?

A: If there is still a virtual console session running for your VM, you will still see processes associated with it for mouse, keyboard, and screen (MKS) even though it is powered off.

Q: I accidently unmounted the VMFS volume on my ESX Server. How can I re-mount the volume without re-booting

A: You can type mount t vmfs vmfs /vmfs
Q: What software is qualified for use with VMware 2.5.1?

A: Please see http://vmware.com/pdf/esx_backup_guide.pdf for an up-to-date list of software that's compatible with ESX.

Q: What SANs are compatible with ESX Server?

A: Please see http://vmware.com/pdf/esx_SAN_guide.pdf for details on ESX-to-SAN server compatibility.

Q: What are the certified backup tools for ESX?

A: Please see http://vmware.com/support/esx25/doc/backup_tools_links.html.

Q: Can I back up my entire virtual machine from the Service Console?

A: Yes, but it is not advised. The console services should be left alone to manage the entire virtual machine infrastructure. It's best that backups be performed by separating the applications and data from the operating systems because backups can become quite large very quickly. You should consider a backup of the environments that change frequently (data and applications) with an agent specifically designed to perform this function. A backup of those virtual disks that change infrequently and need VMFS formats should be backed up from the Service Console. These console-based backups should be performed in a powered-down or suspended approach (preferred), or a suspended environment using redo logs as an alternative. All backups performed from a systems console mode must be restored in an all-or-nothing approach. Recovery for a single file or directory can only be accomplished via a backup agent or from a backup to a SAN environment using a variety of different recovery/restoral techniques.
Q: I'm not able to connect to the Service Console over the network. What could the issue be?

A: You may have allocated the Service Console NIC to the VMkernel. Use vmkpcidivyi to reassign the NIC to the Service Console.

Q: I have a virtual machine that did not start up correctly, but now I can't power it down from the MUI or Virtual Center. How can I get this VM to shut down?

A: You can use the vmware-cmd utility to force a hard power down. The following syntax should work:

vmware-cmd /path-to-vm/vm-directory/vm.vmx stop hard

Q: I find using commands to be very difficult. Why can't I use X Windows on the Service Console?

A: You actually could run the X Windows system on the Service Console, but it will eat up valuable resources that are needed by the system to manage all the processes related to Virtualization. VMware specifically says not to run X Windows on the Service Console. So, it's best to just buck up and deal with it.

Q: Is there a way to mount the vmfs volumes if they accidentally get unmounted without having to reboot?

A: Yes. You can run mountt vmfs vmfs /vmfs.

Q: How do I check the speed and duplex setting of the Service Console NIC? Also, how do I change it if needed?

A: You'll need to cat out the eth0.info file for your type of adapter. This file can be found at /proc/net/type-of-nic/eth0.info. To give you an example, our server has an Intel Pro 100 Nic for the Service Console, so for us to find the speed and duplex information we would type: cat /proc/net/PRO_LAN_Adapters/eth0.info.
Q: How long has Xen been around?

A: Since 2004, and they're located in Palo Alto, California. Hmm…what other virtualization company is in Palo Alto?

Q: What is a hypervisor?

A: In VMware parlance, it's the virtualization layer.

Q: Why did VMware limit its beta of ESX Server 3.0 to so few?

A: Good question…We don't know, and we hope that VMware's future beta programs are opened up to a larger audience.

Q: If I can't get a SAN, will local storage with a RAID device be sufficient?

A: Absolutely. You won't get some of the cooler tools like VMotion, but being virtual on local storage is better than remaining physical.

Q: Explain about your production environment? How many cluster’s, ESX, Data Centers, H/w etc ?

Q: How does VMotion works? What’s the port number used for it?
A: TCP port 8000

Q: Prerequisites for VMotion?
A:

1)ESX Servers must be configured with VMkenerl ports enabled for vmotion and on the same network segment
2)ESX Servers must be managed by the same Virtual Center server
3)ESX Must have compatible CPUs
4)ESX Servers muct have consisten Networks and NEtwroks labels
5)The VMs must be stored on shared storage - iSCSI or FC SAN or NAS/NFS
6)The VMs can not use localcd/floppy or internal only vrtual switches on the ESX server

Check out http://www.vmware.com/pdf/vi3_35/esx_3/r35u2/vi3_35_25_u2_admin_guide.pdf for more information

Q: How does HA works? Port number? How many host failure allowed and why? 
A: Maximum allowed host failures within a HA cluster is 4. What happens if 4 hosts have failed and a 5th one also fails.
Q: I have still enough free resources to start up the virtual machines on the remaining hosts. Will HA start these virtual machines from the 5th failed host on the remaining hosts?
ANS) That depends. If you have admission control enabled, if there are any resource constraints some VM's may not restart. If you have admission control disabled, the VM's will get restarted on any host left in the cluster. However, that doesn't mean they will be functional. Make sure you have enough port groups configured on your vSwitch for your Virtual Machine port group to accommodate

Host Firewalls. On ESX/ESXi hosts, VMware HA needs and automatically opens the following firewall ports.
Incoming port: TCP/UDP 8042-8045
Outgoing port: TCP/UDP 2050-2250

Q: What are active host / primary host in HA? Explain it?
A:
When you add a host to a VMware HA cluster, an agent is uploaded to the host and configured to communicate
with other agents in the cluster. The first five hosts added to the cluster are designated as primary hosts, and
all subsequent hosts are designated as secondary hosts. The primary hosts maintain and replicate all cluster
state and are used to initiate failover actions. If a primary host is removed from the cluster, VMware HA
promotes another host to primary status.
Any host that joins the cluster must communicate with an existing primary host to complete its configuration
(except when you are adding the first host to the cluster). At least one primary host must be functional for
VMware HA to operate correctly. If all primary hosts are unavailable (not responding), no hosts can be
successfully configured for VMware HA.

One of the primary hosts is also designated as the active primary host and its responsibilities include:
n Deciding where to restart virtual machines.
n Keeping track of failed restart attempts.
n Determining when it is appropriate to keep trying to restart a virtual machine.
If the active primary host fails, another primary host replaces it.

Q: Prerequisites for HA ?
A:First, for clusters enabled for VMware HA, all virtual machines and their configuration files must
reside on shared storage (Fibre Channel SAN, iSCSI SAN, or SAN iSCI NAS), because you need to
be able to power on the virtual machine on any host in the cluster.
Second, VMware HA monitors heartbeat between hosts on the console network for failure
detection. So, to have reliable failure detection for HA clusters, the console network should have
redundant network paths. That way, if a host's first network connection fails, the second
connection can broadcast heartbeats to other hosts.
Last, if you want to use DRS with HA for load balancing, the hosts in your cluster must be part of
a VMotion network. If the hosts are not in the VMotion network, however, DRS can still make
initial placement recommendations.

Q: How do DRS works? Which technology used? What are the priority counts to migrate the VM’s?
Q: How does snap shot’s works?
Q: What are the files will be created while creating a VM and after powering on the VM?
Q: If the VMDK header file corrupt what will happen? How do you troubleshoot?
Q: Prerequisites VC, Update manager?
Q:  Have you ever patched the ESX host? What are the steps involved in that?
Q:  Have you ever installed an ESX host? What are the pre and post conversion steps involved in that? What would be the portions listed? What would be the max size of it?
Q:  I turned on Maintenance mode in an ESX host, all the VM’s has been migrated to another host, but only one VM failed to migrate? What are the possible reasons?
Q:  How will you turn start / stop a VM through command prompt?
Q:  I have upgraded a VM from 4 to 8 GB RAM; it’s getting failed at 90% of powering on? How do you troubleshoot?
Q:  Storage team provided the new LUN ID to you? How will you configure the LUN in VC? What would be the block size (say for 500 GB volume size)?
Q:  I want to add a new VLAN to the production network? What are the steps involved in that? And how do you enable it?
Q:  Explain about VCB? What it the minimum priority (*) to consolidate a machine?
Q:  How VDR works?
Q:  What’s the difference between Top and ESXTOP command?
Q:  How will you check the network bandwidth utilization in an ESXS host through command prompt?
Q:  How will you generate a report for list of ESX, VM’s, RAM and CPU used in your Vsphere environment?
Q:  What the difference between connecting the ESX host through VC and Vsphere? What are the services involved in that? What are the port numbers’s used?
Q:  How does FT works? Prerequisites? Port used?
Q:  Can I VMotion between 2 different data centers? Why?
Q:  Can I deploy a VM by template in different data centers ?
Q: I want to increase the system partition size (windows 2003 server- Guest OS) of a VM? How will you do it without any interruption to the end user?
Q:  Which port number used while 2 ESX transfer the data in between?
Q:  Unable to connect to a VC through Vsphere client? What could be the reason? How do you troubleshoot?
Q:  Have you ever upgraded the ESX 3.5 to 4.0? How did you do it?
Q:  What are the Vsphere 4.0, VC 4.0, ESX 4.0, VM 7.0 special features?
Q: What is AAM? Where is it used? How do you start or stop through command prompt?
A: VMware-aam = HA.
VMware purchased the HA technology from Legato, who originally coined it as "Automated Availability Manager".

Q: Have you ever called VMWare support? Etc

Q: Explain about Vsphere Licensing? License server?

Q: How will you change the service console IP?
A:Note: ESX 4.0 Update 2 introduces a new tool that simplifies the process of creating or restoring networking in the ESX service console. For more information, see Configuring or restoring networking from the ESX service console using console-setup (1022078).

Changing settings from the physical or remote console connection
Changing the IP for the Service Console must be done from the physical console or through a remote console session. If you make changes through a network connection such as SSH, network connectivity to the Service Console disconnects because the Service Console's network interface changes.

1.Run this command to set the IP address:

[root@server root]# esxcfg-vswif -i -n vswif0

where is the IP address and is the subnet mask.

Note: In this example, vswif0 is the Service Console adapter that is the interface to which you are applying the IP address change.


2.Open the /etc/hosts file with a text editor and modify it so that it reflects the correct IP address and hostname.
3.To change the default gateway address and the hostname, edit the /etc/sysconfig/network file and change the GATEWAY and HOSTNAME parameters to the proper values.
4.For the changes to take place, restart the network service with the command:

[root@server root]# service network restart

Note: If you are required to edit the hostname, then you must reboot the host.

Note: This command breaks any current network connections to the Service Console, but virtual machines continue to have network connection. If the ESX host is managed by VirtualCenter or vCenter Server, you may have to remove and re-add the host to the inventory. For more information, see ESX not working properly in VirtualCenter after IP address change (1005633).
Note: Making changes to IP and DNS server settings can have a negative impact on the normal operation of ESX/ESXi, particularly in HA clustered environments. For more information, see Identifying issues with and setting up name resolution on ESX/ESXi Server (1003735).

Note: If the changed IP does not persist across a reboot, try deleting and recreating the Service Console vswif management interface. For more information, see Recreating Service Console networking from the command line (1000266).
Changing the hostname without rebooting
To dynamically change the hostname, run the command:

[root@server root]# hostname newname

Note: This command creates a temporary hostname change. This change is lost when the system is rebooted.

Changing the DNS server settings
To change the DNS server settings, update the nameserver IPs and search domain in the /etc/resolv.conf file.

Changing settings in VMware vSphere or Infrastructure Client
To change the hostname, domain, DNS servers, and default gateway in VMware vSphere or Infrastructure Client:

1.Highlight the ESX host and click the Configuration tab.
2.Click DNS and Routing.
3.Click Properties.
4.To change the hostname, domain, and DNS servers, click the DNS Configuration tab and enter the appropriate values.

Note: Disable VMware High Availability if you do not want virtual machines to failover during the hostname IP change.

5.To change the default gateway, click the Routing tab and enter the appropriate value.
6.Reboot the ESX host for the changes to take effect .
7.Reconnect the ESX host to vCenter Server with the new IP address.
Generating new certificates for the ESX host
The ESX host generates certificates the first time the system is started. Under certain circumstances, it might be required to force the host to generate new certificates. Typically new certificates only need to be generated if the hostname has been changed or the certificates have been deleted accidentally.

Each time you restart the vmware-hostd process, the mgmt-vmware script searches for existing certificate files ( rui.crt and rui.key). If the files cannot be found, new certificate files are generated.

To generate new certificates:

1.Put the host into Maintenance Mode.
2.In the directory /etc/vmware/ssl, back up any existing certificates by renaming them with these commands:

[root@server root]# mv /etc/vmware/ssl/rui.crt /etc/vmware/ssl/orig.rui.crt
[root@server root]# mv /etc/vmware/ssl/rui.key /etc/vmware/ssl/orig.rui.key

Note: If you are regenerating certificates because you accidentally deleted them, you do not have to rename them.

3.Reboot your host to allow it to begin using the new certificate, or restart the host services:

a.Restart hostd, using this command:

service mgmt-vmware restart

b.Restart vmkauthd, using this command:

service vmware-vmkauthd restart

4.Exit Maintenance Mode.
5.Confirm that the ESX host successfully generated new certificates by running this command and comparing the time stamps of the new certificate files with orig.rui.crt and orig.rui.key:

[root@server root]# ls -la /etc/vmware/ssl/rui*
Notes:

•Disable VMware High Availability if you do not want virtual machines to failover during the hostname IP change. If you are using vSphere 4.x you can just disable host monitoring in the HA settings.
•For related information, see Verifying ESX Server host networking configuration on the service console (1003796).
•You may be required to regenerate your SSL certificate. For more information, see Replacing or Regenerating an SSL Certificate for the Management Interface (1843).
•You are required to edit files on an ESX host. For more information, see Editing files on an ESX host using vi or nano (1020302).
•For information on replacing VirtualCenter Server ceritificates, see:
?Replacing VirtualCenter Server Certificates in Virtual Infrastructure 3
?Replacing VirtualCenter Server Certificates in vSphere 4
•The iSCSI Qualified Name used for iSCSI storage configuration is based on the hostname of the ESX host. If you change the hostname of the ESX host, ensure to review your iSCSI software initiator configuration. For more information on iSCSI troubleshooting, see Configuring and troubleshooting basic software iSCSI setup (1008083).
•For more information on changing the hostname, see Changing the name of an ESX host (1010821).

Q: What’s the difference between ESX and ESXi?
Q:  What’s the difference between ESX 3.5 and ESX 4.0?

Q: P2V Prt Number and Log file location?
TCP/IP Ports Required by VMware Converter
Table lists the ports Converter uses in the conversion process.
If your VirtualCenter Servers or ESX Servers are configured to listen on port 905, you will have to make
adjustments accordingly.
Communication Paths | Port
Converter application to remote physical machine | 445 and 139
Converter application to VirtualCenter Server | 902
Converter application to ESX Server 3.x | 902
Physical machine to VirtualCenter Server | 902
Physical machine to ESX Server 3.x | 902
Log File Locations:
UFAD logs:
%WINDIR%\Temp\vmware-temp\vmware-converter*
%WINDIR%\vmware-temp\vmware-converter* (in Windows NT)
Client logs:
%TEMP%\vmware-temp\vmware-client*

Send these in to support using File > Export Logs. For Converter Boot CD, map a network drive using the

What is  VMware HA?

As per VMware Definition,
VMware® High Availability (HA) provides easy to use, cost effective high availability for applications running in virtual machines. In the event of server failure, affected virtual machines are automatically restarted on other production servers with spare capacity

Download Now and Complete your End to End P2v Migrations using VMware Arena’s ”P2V ADMIN ISO“

What is AAM in HA?

AAM is the Legato automated availability management.  Prior to vSphere 4.1, VMware’s HA is actually re engineered to work with VM’s with the help of  Legato’s Automated Availability Manager (AAM) software. VMware’s vCenter agent (vpxa) interfaces with the VMware HA agent which acts as an intermediary to the AAM software. From vSphere 5.0, it uses an agent called “FDM”  (Fault Domain Manager).

What are pre-requites for HA to work?

1.Shared storage for the VMs running in HA cluster
2.Essentials plus, standard, Advanced, Enterprise and Enterprise Plus Licensing
3.Create VMHA enabled Cluster
4.Management network redundancy to avoid frequent isolation response in case of temporary network issues (preferred not a requirement)

What is maximum number of primary HA hosts in vSphere 4.1?

Maximum number of primary HA host is 5. VMware HA cluster chooses the first 5 hosts that joins the cluster as primary nodes and all others hosts are automatically selected as secondary nodes.

How to see the list of Primary nodes in HA cluster?

View the log file named “aam_config_util_listnodes.log” under /var/log/vmware/aam using the below command

cat /var/log/vmware/aam/aam_config_util_listnodes.log

What is the command to restart /Start/Stop HA agent in the ESX host?

service vmware-aam restart

service vmware-aam stop

service vmware-aam start

Where to located HA related logs in case of troubleshooting?

/Var/log/vmware/aam

What the basic troubleshooting steps in case of HA agent install failed on hosts in HA cluster?

Below steps are are taken from my blog posts Troubleshooting HA

1. Check for some network issues

2. Check the DNS is configured properly

3. Check the vmware HA agent status in ESX host by using below commands

  service vmware-aam status

4. Check the networks are properly configured  and named exactly as other hosts in the cluster. otherwise, you will get the below errors while installing or reconfiguring HA agent.

5. Check HA related ports are open in firewall to allow for the communication
    
     Incoming port: TCP/UDP 8042-8045
     Outgoing port: TCP/UDP 2050-2250

6. First try to restart /stop/start the vmware HA agent on the affected host using the below commands. In addition u can also try to restart vpxa and management agent in the Host.

        service vmware-aam restart

        service vmware-aam stop

        service vmware-aam start

7. Right Click the affected host and click on “Reconfigure for VMWare HA” to re-install the HA agent that particular host.

8. Remove the affected host from the cluster. Removing ESX host from the cluster will not be allowed untill that host is put into maintenance mode.

9.Alternative solution for 3 step is, Goto cluster settings and uncheck the vmware HA in toturnoff the HA in that cluster and re-enable the vmware HA to get the agent installed.

10. For further troubleshooting , review the HA logs under /Var/log/vmware/aam directory.

What is the maximum number of hosts per HA cluster?

Maximum number of hosts in the HA cluster is 32

What is Host Isolation?

VMware HA has a mechanism to detect a host is isolated from rest of hosts in the cluster. When the ESX host loses its ability to exchange heartbeat via management network between the other hosts in the HA cluster, that ESX host will be considered as a Isolated.

How Host Isolation is detected?

In HA cluster, ESX hosts uses heartbeats to communicate among other hosts in the cluster.By default, Heartbeat will be sent every 1 second.

If a ESX host in the cluster didn’t received heartbeat for for 13 seconds from any other hosts in the cluster, The host considered it as isolated and host will ping the configured isolation address(default gateway by default). If the ping fails, VMware HA will execute the Host isolation response

What are the different types isolation response available in HA?

Power off –  All the VMs are powered off , when the HA detects that the network isolation occurs

Shut down – All VMs running on that host are shut down with the help of VMware Tools, when the HA detects that the network isolation occurs.If the shutdown via VMWare tools not happened within 5 minutes, VM’s power off operation will be executed. This behavior can be changed with the help of HA advanced options. Please refer my Post on HA Advanced configuration

Leave powered on –  The VM’s state remain powered on or remain unchanged, when the HA detects that the network isolation occurs.

How to add additional isolation address for redundancy?

By default, VMWare HA use to ping default gateway as the isolation address if it stops receiving heartbeat.We can add an additional values in case if we are using redundant service  console both belongs to different subnet.Let’s say we can add the default gateway of SC1 as first value and gateway of SC2 as the additional one using the below value

1. Right Click your HA cluster

2. Goto to advanced options of HA

3. Add the line “das.isolationaddress1 = 192.168.0.1″

4. Add the line “das.isolationaddress2 = 192.168.1.1″ as the additional isolation address

To know more about the Advanced HA Options

What is HA Admission control?

As per “VMware Availability Guide”,

VCenter Server uses admission control to ensure that sufficient resources are available in a cluster to provide failover protection and to ensure that virtual machine resource reservations are respected.

What are the 2 types of settings available for admission control?

Enable: Do not power on VMs that violate availability constraints

Disable: Power on VMs that violate availability constraints

What are the different types of Admission control policy available with VMware HA?

There are 3 different types of Admission control policy available.

Host failures cluster  tolerates
Percentage of cluster resources reserved as fail over spare capacity
Specify a fail over host

How the Host Failures cluster tolerates admission control policy works?

Select the maximum number of host failures that you can afford for or to guarantee fail over. Prior vSphere 4.1, Minimum is 1 and the maximum is 4.

In the Host Failures cluster tolerates admission control policy , we can define the specific number of hosts  that can fail  in the cluster and also it ensures that the sufficient resources remain to fail over all the virtual machines from that failed hosts to the other hosts incluster. VMware High Availability(HA) uses a mechanism called slots to calculate both the available and required resources in the cluster for a failing over virtual machines from a failed host  to other hosts in the cluster.

What is SLOT?

As per VMWare’s Definition,

“A slot is a logical representation of the memory and CPU resources that satisfy the requirements for any powered-on virtual machine in the cluster.”

If you have configured reservations at VM level, It influence the HA slot calculation. Highest memory reservation and highest CPU reservation of the VM in your cluster determines the slot size for the cluster.

How the HA Slots are Calculated?

I have written a post about how the HA slots are calculated.

How to Check the HA Slot information from vSphere Client?

Click on Cluster Summary Tab and Click on “Advanced Runtime Info” to see the the detailed HA slots information.

What is use of Host Monitoring  status in HA cluster?

Let’s take an example, you are performing network maintenance activity on your switches which connects your one of th ESX host in HA cluster.

what will happen if the switch connected to the ESX host in HA cluster is down?

It will not receive heartbeat and also ping to the isolation address also failed. so, host will think itself as isolated and HA will initiate the reboot of virtual machines on the host to other hosts in the cluster. Why do you need this unwanted situation while performing scheduled maintenance window.

To avoid the above situation when performing scheduled activity which may cause ESX hostto isolate, remove the check box in ” Enable Host Monitoring” until you are done with the network maintenance activity.

How to Manually define the HA Slot size?

By default, HA slot size is determined by the Virtual machine Highest CPU and memory reservation. If no reservation is specified at the VM level, default slot size of 256 MHZ for CPU and 0 MB + memory overhead for RAM will be taken as slot size. We can control the HA slot size manually by using the following values.

There are 4 options we can configure at HA advanced options related to slot size

das.slotMemInMB – Maximum Bound  value for HA memory slot size
das.slotCpuInMHz – Maximum Bound value for HA CPU slot Size
das.vmMemoryMinMB –  Minimum Bound  value for HA memory slot size
das.vmCpuMinMHz –  Minimum Bound  value for HA CPU slot size

For More HA related Advanced options, Please refer my blog post

How the “Percentage of cluster resources reserved as failover spare capacity” admission control policy works?

In the Percentage of cluster resources reserved as failover spare capacity admission control policy, We can define the specific percentage of total cluster resources are reserved for failover.In contrast to the “Host Failures cluster tolerates admission control policy”, It will not use slots. Instead This policy calculates the in the way below

1.It calculates the Total resource requirement for all Powered-on Virtual Machines in the cluster  and also calculates the total resource available in host for virtual machines.
2.It calculates the current CPU and Memory Failover capacity for the capacity.
3.If the current CPU and Memory Failover capacity for the cluster < configured failover capacity (ex 25 %)
4.Admission control will not allow to power on the virtual machine which violates the availability constraints.

How the “Specify a failover host” admission control policy works?

In the Specify a failover host” admission control policy, We can define a specific host as a dedicated failover host. When isolation response is detected, HA attempts to restart the virtual machines on the specified failover host.In this Approach, dedicated failover hist will be sitting idle without actively involving or not participating in DRS load balancing.DRS will not migrate or power on placement of virtual machines on the defined failover host.

What is VM Monitoring status?

HA will usually monitors ESX hosts and reboot the virtual machine in the failed hosts in the other host in the cluster in case of host isolation but i need the HA to monitors for Virtual machine failures also. here the feature called VM monitoring status as part of HA settings.VM monitoring restarts the virtual machine if the vmware tools heartbeat didn’t received withthe specified time using Monitoring sensitivity.

If you are looking for more VMware interview questions Please click  Interview Questions.

Thanks For Reading!!! All the Best…

2. The VMKernel can't boot it by itself, so that it takes the help of the 3rd party operating system. In VMWare case the kernel is booted by RedHat Linux operating system which is known as service console. 

3. The service console is developed based up on Redhat Linux Operating system, it is used to manage the VMKernel  

4. To restart webaccess service on vmware
service vmware-webaccess restart – this will restart apache tomcat app 

5. To restart ssh service on vmware
service sshd restart 

6. To restart host agent(vmware-hostd) on vmware esx server
service mgmt-vmware restart 

7. Path for the struts-config.xml
/usr/lib/vmware/webAccess/tomcat/apache-tomcat-5.5.17/webapps/ui/WEB-INF/ 

8. To start the scripted install the command is
    esx ks=nfs:111.222.333.444:/data/KS.config ksdevice=eth0
               location                                             device name

9. Virtual Network in Simple……………….

Virtual Nic(s) on Virtual Machine(s) -----> 

Physical Nic on the ESX Server (Virtual Switch - 56 Ports)  ----->

Physical Switch Port Should be trunked with all the VLANS to which the VM's need access  

All the ESX servers should be configured with Same number of Physical Nics (vSwitches) and Connectivity also should be same, So that vMotion succeeds
All the Virtual Machines are connected to one vSwitch with Different VLANS, this means the Physical Nic(vSwitch) needs to be trunked with the same VLANS on the Physical Switch Port

10 What are the three port groups present in ESX server networking
   1. Virtual Machine Port Group - Used for Virtual Machine Network
   2. Service Console Port Group - Used for Service Console Communications
   3. VMKernel Port Group - Used for VMotion, iSCSI, NFS Communications

11. What is the use of a Port Group?
The port group segregates the type of communication.

12. What are the type of communications which requires an IP address for sure ?
   Service Console and VMKernel (VMotion and iSCSI), these communications does not happen without an ip address (Whether it is a single or dedicated)

13. In the ESX Server licensing features VMotion License is showing as Not used, why?
    Even though the license box is selected, it shows as "License Not Used" until, you enable the VMotion option for specific vSwitch

 14. How the Virtual Machineort group communication works ? 

     All the vm's which are configured in VM Port Group are able to connect to the physical machines on the network. So this port group enables communication between vSwitch and Physical Switch to connect vm's to Physical Machine's

15. What is a VLAN ?
     A VLAN is a logical configuration on the switch port to segment the IP Traffic. For this to happen, the port must be trunked with the correct VLAN ID.

Back to the top

16. Does the vSwitches support VLAN Tagging? Why? 
     Yes, The vSwitches support VLAN Tagging, otherwise if the virtual machines in an esx host are connected to different VLANS, we need to install a separate physical nic (vSwitch) for every VLAN. That is the reason vmware included the VLANtagging for vSwitches. So every vSwitch supports upto 1016 ports, and BTW they can support 1016 VLANS if needed, but an ESX server doesn’t support that many VM’s. :)  

17. What is Promiscuous Mode on vSwitch ? What happens if it sets to Accept?
     If the promiscuous mode set to Accept, all the communication is visible to all the virtual machines, in other words all the packets are sent to all the ports on vSwitch
     If the promiscuous mode set to Reject, the packets are sent to inteded port, so that the intended virtual machine was able to see the communication.

18. What is MAC address Changes ? What happens if it is set to Accept ?
When we create a virtual machine the configuration wizard generates a MAC address for that machine, you can see it in the .vmx (VM Config) file. If it doesn't matches with the MAC address in the OS this setting does not allow incoming traffic to the VM. So by setting Reject Option both MAC addresses will be remains same, and the incoming traffic will be allowed to the VM.

19. What is Forged Transmits ? What happens if it is set to Accept ?
When we create a virtual machine the configuration wizard generates a MAC address for that machine, you can see it in the .vmx (VM Config) file. If it doesn't matches with the MAC address in the OS this setting does not allow outgoing traffic from the VM. So by setting Reject Option both MAC addresses will be remains same, and the outgoing traffic will be allowed from the VM.

20. What are the core services of VC ?
VM provisioning , Task Scheduling and Event Logging

21. Can we do vMotion between two datacenters ? If possible how it will be?
Yes we can do vMotion between two datacenters, but the mandatory requirement is the VM should be powered off.

22. What is VC agent? and what service it is corresponded to? What are the minimum req's for VC agent installation ?
VC agent is an agent installed on ESX server which enables communication between VC and ESX server.
The daemon  associated with it is called vmware-hostd , and the service which corresponds to it is called as mgmt-vmware, in the event of VC agent failure just restart the service by typing the following command at the service console       

     " service mgmt-vmware restart " 
VC agent installed on the ESX server when we add it to the VC, so at the time of installtion if you are getting an error like " VC Agent service failed to install ", check the /Opt size whether it is sufficient or not.

23. How can you edit VI Client Settings and VC Server Settings ?
Click Edit Menu on VC and Select Client Settings to change VI settings
Click Administration Menu on VC and Select VC Management Server Configuration to Change VC Settings

24. What are the files that make a Virtual Machine  ?
     .vmx - Virtual Machine Configuration File
     .nvram - Virtual Machine BIOS
     .vmdk - Virtual Machine Disk file
     .vswp - Virtual Machine Swap File
     .vmsd - Virtual MAchine Snapshot Database
     .vmsn - Virtual Machine Snapshot file
     .vmss - Virtual Machine Suspended State file
     .vmware.log - Current Log File
     .vmware-#.log - Old Log file

25. What are the devices that can be added while the virtual Machine running
In VI 3.5 we can add Hard Disk and NIC's while the machine running.

In vSphere 4.0 we can add Memory and Processor along with HDD and NIC's while the machine running 

26. How to set the time delay for BIOS screen for a Virtual Machine?
Right Click on VM, select edit settings, choose options tab and select boot option, set the delay how much you want.

27. What is a template ?
We can convert a VM into Template, and it cannot be powered on once its changed to template. This is used to quick provisioning of VM's.

23. What to do to customize the windows virtual machine clone,?
copy the sysprep files to Virtual center directory on the server, so that the wizard will take the advantage of it.

24. What to do to customize the linux/unix virtual machine clone,?
VC itself includes the customization tools, as these operating systems are available as open source.

25. Does cloning from template happens between two datacenters ?
Yes.. it can, if the template in one datacenter, we can deploy the vm from that template in another datacenter without any problem.

26. What are the common issues with snapshots? What stops from taking a snapshot and how to fix it ?
If you configure the VM with Mapped LUN's, then the snapshot failed. If it is mapped as virtual then we can take a snapshot of it.
If you configure the VM with Mapped LUN's as physical, you need to remove it to take a snapshot.

27. What are the settings that are taken into to consideration when we initiate a snapshot ?
Virtual Machine Configuration (What hardware is attached to it)
State of the Virtual Machine Hard Disk file ( To revert back if needed)
State of the Virtual Machine Memory (if it is powered on)

28. What are the requirements for Converting a Physical machine to VM ?
An agent needs to be installed on the Physical machine
VI client needs to be installed with Converter Plug-in
A server to import/export virtual machines

29. What is VMWare consolidated backup ?
It is a backup framework, that supports 3rd party utilities to take backups of ESX servers and Virtual Machines. Its not a backup service.

30. To open the guided consolidation tool, what are the user requirements ?
The user must be member of administrator, The user should have "Logon as service" privileges - To give a user these privileges,open local sec policy, select Logon as service policy and add the user the user should have read access to AD to send queries

 What is Service Console?

The service console is developed based up on Redhat Linux Operating system, it is used to manage the VMKernel

What are the basic commands to troubleshoot  connectivity between vSphere Client /vCenter to ESX server?

service mgmt-vmware restart  (restarts host agent(vmware-hostd) on vmware esx server)

service vmware-vpxa restrat (restarts Vcenter agent service)

service network restart (restarts management networks on ESX)

What is vCenter Agent?

VC agent is an agent installed on ESX server which enables communication between VC and ESX server. This Agent will be installed on ESX/ESXi will be done when you try to add the ESx host in Vcenter.

What is the command used to restart SSH, NTP & Vmware Web access?

Service sshd restart

Service ntpd restrat

Service vmware-webaccess restart

What are the types of Ports groups in ESX/ESXi?

There are 3 types of port groups in ESX

1.Service console port group
2.VMkernel Port group
3. Virtual machine port group

There are only 2 types of port group in ESXi

1. Vmkernel Port group
2.Virtual Machine Port group

What is VMKernel ?

VMWare Kernel is a Proprietary kernel  of vmwareand is not based on any of the flavors of Linux operating systems, .VMkernel requires an operating system to boot and manage the kernel. A service console is being provided when VMWare kernel is booted. Only service console is based up on Redhat Linux OS not VMkernel.

What is the use of Service Console port ?

Service console port group required to manage the ESX server and it acts as the management network for the ESX. Vcenter/Vsphere Client uses the service console IP’s to communicate with the ESX server.

What is the use of VMKernel Port ?

Vmkernel port is used by ESX/ESXi for vmotion, ISCSI & NFS communications. ESXi uses Vmkernel as the management network  since it don’t have service console built with it.

What is the use of Virtual Machine Port Group?

Virtual Machine port group is used by Virtual machine communication.

How Virtual Machine communicates to another servers in Network ?

All the Virtual Machines which are configured in VM Port Group are able to connect to the other machines on the network. So this port group enables communication between vSwitch and Physical Switch by the use of uplink (Physical NIC) associated with the port group.

What is the default number of ports configured with the Virtual Switch?

When the time of Virtual switch created, Vswitch is created with 56 ports by default. We can extend the no of ports by editing the vswitch properties.

What are the different types of Partitions in ESX server?

/ -root
Swap
/var
/Var/core
/opt
/home
/tmp

What are the security options available for ESX vswitch?

Promiscuous Mode – Reject
MAC Address changes – Accept
Forged Transmits – Accept

What is Promiscuous Mode ?

If the promiscuous mode set to Accept, all the communication is visible to all the virtual machines, in other words all the packets are sent to all the ports on vSwitch. It can be useful when you are running virtual machines with network sniffers to capture packet in that network.

What is MAC Address changes?

All the virtual machines nics are provide with the MAC address at the time of creation and it is stored in .VMX file. If the packet  doesn’t match with the MAC address as same as in the .VMX  file , it does not allow incoming traffic to the VM by setting this option as reject.

If it is set as Accept,ESX accepts requests to change the effective MAC address to other than the MAC address save din the .VMX file.

What is Forged Transmits ?

Which is same as the Mac Address changes setting but it worked for the outgoing traffic but the MAC address changes setting is for incoming traffic.

What is a VLAN ?

A VLAN is the Virtual LAN which is used to broke down the Broadcast traffic into many logical groups. Basically, one physical switch comprise of one broadcast domain. VLAN used to separate the one broadcast domain into many small pieces to separate the networks within the broadcast domain.


What are the types of VLAN tagging in Vsphere?

There are 3 types of VLAN tagging available in Vsphere.

1.Virtual Switch Tagging (VST)
2.External Switch Tagging (EST)
3.Virtual Guest Tagging (VGT)

What is VST , EST & VGT?

Please refer my blog post on VST , EST & VGT .

What are the Traffic Shaping policies available in the Vswitch?

Traffic shaping policies are disabled by default. There are 3 different traffic shaping policy setting

Average Bandwidth
Peak Bandwidth
Burst Size

Average Bandwidth is defined in KBPS
Peak bandwidth is defined in KBPS
Burst Size is defined in Kilobytes

What are the Load balancing policies available in vswitch?

Route based on the originating virtual switch port ID
Route based on source MAC hash
Route based on IP hash

Route based on the originating virtual switch port ID – Chooses an uplink based on the virtual port where the traffic entered the virtual switch.  The traffic will be always send with that same uplink until that particular uplink is failed and failed over to another NIC.

Route based on source MAC hash – Choose an uplink based on a hash of the source Ethernet MAC address.The traffic will be always send with that same uplink until that particular uplink is failed and failed over to another NIC.

Route based on IP hash – Choose an uplink based on a hash of the source and destination IP addresses of each packet.

What are the  types for Network Failover Detection settings?

Link Status only
Beacon Probing

Link Status only – Relies solely on the link status provided by the network adapter. This detects failures, such as cable pulls and physical switch power failures, but it cannot detect configuration errors, such as a physical switch port being blocked by spanning tree or misconfigured to the wrong VLAN or cable pulls on the other side of a physical switch.

Beacon Probing –  Sends out and listens for beacon probes — Ethernet broadcast frames sent by physical adapters to detect upstream network connection failures — on all physical Ethernet adapters in the team. In addition to link status, to determine link failure. This detects many of the failures which are not detected by Link Status.

What is the command to  check the IP address along with the detailed network cards assigned to the esx server?

Ifconfig -a

Output appears like this
========================================================================

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:9365 errors:0 dropped:0 overruns:0 frame:0
          TX packets:9365 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:8127714 (7.7 MiB)  TX bytes:8127714 (7.7 MiB)

vmnic0    Link encap:Ethernet  HWaddr 00:0C:29:85:0D:76
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:100772 errors:0 dropped:0 overruns:0 frame:0
          TX packets:5103 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:35475848 (33.8 MiB)  TX bytes:402120 (392.6 KiB)
          Interrupt:145

vmnic1    Link encap:Ethernet  HWaddr 00:0C:29:85:0D:80
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:105895 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:35894203 (34.2 MiB)  TX bytes:0 (0.0 b)
          Interrupt:129

vmnic2    Link encap:Ethernet  HWaddr 00:0C:29:85:0D:8A
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:105908 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:35895750 (34.2 MiB)  TX bytes:0 (0.0 b)
          Interrupt:137

vmnic3    Link encap:Ethernet  HWaddr 00:0C:29:85:0D:94
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:105690 errors:0 dropped:0 overruns:0 frame:0
          TX packets:228 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:35883279 (34.2 MiB)  TX bytes:13680 (13.3 KiB)
          Interrupt:145

vswif0    Link encap:Ethernet  HWaddr 00:50:56:4D:69:D1
          inet addr:192.168.0.75  Bcast:192.168.0.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:14893 errors:0 dropped:0 overruns:0 frame:0
          TX packets:2575 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:966513 (943.8 KiB)  TX bytes:230028 (224.6 KiB)

vswif1    Link encap:Ethernet  HWaddr 00:50:56:4F:45:B1
          BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:11042 errors:0 dropped:0 overruns:0 frame:0
          TX packets:30 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:717158 (700.3 KiB)  TX bytes:1260 (1.2 KiB)

=========================================================================

You can use “ip addr” command also to view the ip information

=========================================================================

[root@ESXTEST1 etc]# ip addr
1: lo: mtu 16436 qdisc noqueue
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
2: vmnic0: mtu 1500 qdisc noop qlen 1000
    link/ether 00:0c:29:85:0d:76 brd ff:ff:ff:ff:ff:ff
3: vmnic1: mtu 1500 qdisc noop qlen 1000
    link/ether 00:0c:29:85:0d:80 brd ff:ff:ff:ff:ff:ff
4: vmnic2: mtu 1500 qdisc noop qlen 1000
    link/ether 00:0c:29:85:0d:8a brd ff:ff:ff:ff:ff:ff
5: vmnic3: mtu 1500 qdisc noop qlen 1000
    link/ether 00:0c:29:85:0d:94 brd ff:ff:ff:ff:ff:ff
6: vswif0: mtu 1500 qdisc pfifo_fast qlen 1000
    link/ether 00:50:56:4d:69:d1 brd ff:ff:ff:ff:ff:ff
    inet 192.168.0.75/24 brd 192.168.0.255 scope global vswif0
7: vswif1: mtu 1500 qdisc pfifo_fast qlen 1000
    link/ether 00:50:56:4f:45:b1 brd ff:ff:ff:ff:ff:ff
9: vswif2: mtu 1500 qdisc pfifo_fast qlen 1000
    link/ether 00:50:56:43:92:be brd ff:ff:ff:ff:ff:ff
    inet 192.168.0.96/24 brd 192.168.0.255 scope global vswif2

=========================================================================

what is the command to check the ESX vswitch details, port group and its ip address?

Esxcfg-vswitch -l
Outuput will appear like this:
=========================================================================
[root@ESXTEST1 ~]# esxcfg-vswitch -l
Switch Name    Num Ports   Used Ports  Configured Ports  MTU     Uplinks
vSwitch0       32          4           32                1500    vmnic0

  PortGroup Name      VLAN ID  Used Ports  Uplinks
  Service Console     0        1           vmnic0
  VMkernel            0        1           vmnic0

Switch Name    Num Ports   Used Ports  Configured Ports  MTU     Uplinks
vSwitch1       64          3           64                1500    vmnic2,vmnic1

  PortGroup Name      VLAN ID  Used Ports  Uplinks
  VM-10.0.0 subnet    0        0           vmnic2,vmnic1
  VM-192.168.0 subnet 0        0           vmnic2,vmnic1

Switch Name    Num Ports   Used Ports  Configured Ports  MTU     Uplinks
vSwitch2       64          4           64                1500    vmnic3

  PortGroup Name      VLAN ID  Used Ports  Uplinks
  Service Console 2   0        1           vmnic3
  Vmotion             0        1           vmnic3
=========================================================================
From the above output,
we come to know that we have 3 virtual switches named vSwitch0,vSwitch1 and vSwitch2.
4 uplinks (physical nics in our esx server) Vmnic0,vmnic1,vmnic2,vmnic3.
vswitch0 constains 2 port group (Service Console & VMKernel), vSwitch1 contains 2 virtual machine port group (VM-10.0.0 subnet & VM-192.168.0 subnet) and Vswitch2 contains 2 port group (Service Console 2 & Vmotion) port group.

What is command to get the information about Service console ports and its IP address assigned to it?

esxcfg-vswif -l

Output will appear like this:

=========================================================================
[root@ESXTEST1 ~]# esxcfg-vswif -l
Name     Port Group/DVPort   IP Family IP Address                              Netmask                                 Broadcast        Enabled   TYPE
vswif0   Service Console     IPv4      192.168.0.75                            255.255.255.0                           192.168.0.255    true      STATIC
vswif1   Service Console 2   IPv4      192.168.0.78                            255.255.255.0                           192.168.0.255    false     STATIC
=========================================================================

what is the command to get the information about vmkernel ports and its ip address?
esxcfg-vmknic -l

Output will appear like this:

=========================================================================
[root@ESXTEST1 ~]# esxcfg-vmknic -l
Interface  Port Group/DVPort   IP Family IP Address                              Netmask         Broadcast       MAC Address       MTU     TSO MSS   Enabled Type
vmk0       VMkernel            IPv4      192.168.0.110                           255.255.255.0   192.168.0.255   00:50:56:78:7e:73 1500    65535     true    STATIC
vmk1       Vmotion             IPv4      192.168.0.77                            255.255.255.0   192.168.0.255   00:50:56:76:42:df 1500    65535     true    S
=========================================================================


what is the command to get the information about physical nics installed on ESX server?
esxcfg-vmknic -l

Output will appear like this:
=========================================================================
[root@ESXTEST1 sbin]# esxcfg-nics -l
Name    PCI      Driver      Link Speed     Duplex MAC Address       MTU    Description
vmnic0  02:00.00 e1000       Up   1000Mbps  Full   00:0c:29:85:0d:76 1500   Intel Corporation 82545EM Gigabit Ethernet Controller (Copper)
vmnic1  02:02.00 e1000       Up   1000Mbps  Full   00:0c:29:85:0d:80 1500   Intel Corporation 82545EM Gigabit Ethernet Controller (Copper)
vmnic2  02:03.00 e1000       Up   1000Mbps  Full   00:0c:29:85:0d:8a 1500   Intel Corporation 82545EM Gigabit Ethernet Controller (Copper)
vmnic3  02:04.00 e1000       Up   1000Mbps  Full   00:0c:29:85:0d:94 1500   Intel Corporation 82545EM Gigabit Ethernet Controller (Copper)
========================================================================

What is command to add the new virtual switch named (vswitch3) to our ESX server?

[root@ESXTEST1 sbin]# esxcfg-vswitch -a vswitch3

Now vswitch3 is created without any port group.

======================================================================

Switch Name    Num Ports   Used Ports  Configured Ports  MTU     Uplinks
vswitch3       64          1           64                1500

  PortGroup Name      VLAN ID  Used Ports  Uplinks
========================================================================

What is command to add the new port group  named (mgmt)to vswitch (vswitch 3) ?

[root@ESXTEST1 sbin]# esxcfg-vswitch -A mgmt vswitch3

now port group “mgmt” is added.

=========================================================================
Switch Name    Num Ports   Used Ports  Configured Ports  MTU     Uplinks
vswitch3       64          1           64                1500

  PortGroup Name      VLAN ID  Used Ports  Uplinks
  mgmt                0        0
=========================================================================

How to add the service console port (vswif2) to our newly created port group “mgmt” with the ip addr 192.168.0.79 ?

[root@ESXTEST1 sbin]# esxcfg-vswif -a vswif2 -i 192.168.0.79 -n 255.255.255.0 -p “mgmt”

where i is the ip address, n is subnet mask p is to mentione the port group name
=========================================================================
vswif2   mgmt                IPv4      192.168.0.79                            255.255.255.0                           192.168.0.255    true      STATIC
=========================================================================

 How to add the vmkernal port (vmk2)  to our newly created port group “mgmt” with the ip addr 192.168.0.83?

[root@ESXTEST1 sbin]# esxcfg-vmknic -a  -i 192.168.0.83 -n 255.255.255.0 -p “mgmt”

=========================================================================
vmk2       mgmt                IPv4      192.168.0.83               255.255.255.0   192.168.0.255   00:50:56:7b:bd:36 1500    65535     true    STATIC
=========================================================================

How to change the ip addresss of the existing service console “vswif2″?
nano /etc/sysconfig/network-scripts/ifcfg-vswif2.

Edit the file with your new id address ” 192.168.0.255″ then save and exit.
======================================================
DEVICE=vswif2
HOTPLUG=yes
MACADDR=00:50:56:43:92:be
ONBOOT=yes
PORTGROUP=mgmt
BOOTPROTO=static
BROADCAST=192.168.0.255
DHCPV6C=no
IPADDR=192.168.0.96
IPV6INIT=no
IPV6_AUTOCONF=no
NETMASK=255.255.255.0
======================================================
restart the network service for ip change to take effect:

[root@ESXTEST1 sysconfig]# service network restart
Shutting down interface vswif0:                            [  OK  ]
Shutting down interface vswif2:                            [  OK  ]
Shutting down loopback interface:                          [  OK  ]
Bringing up loopback interface:                            [  OK  ]
Bringing up interface vswif0:                              [  OK  ]

Another way is to connect to the console of the ESX server and at the shell prompt type in :esxcfg-vswif -d vswif2

This will delete the existing vswif0 and it will give the message about “nothing to flush”.

then type the below command

esxcfg-vswif -a vswif2 -p mgmt -i 192.168.0.97 -n 255.255.255.0
=========================================================================
[root@ESXTEST1 etc]# esxcfg-vswif -d vswif2
Nothing to flush.
[root@ESXTEST1 etc]# esxcfg-vswif -a vswif2 -p mgmt -i 192.168.0.97 -n 255.255.255.0
[2011-09-17 19:35:46 'Vnic' warning] Generated New MAC address, 00:50:56:43:92:be for vswif2
Nothing to flush.
=========================================================================

How to change  the  ESX host name and default gateway?

edit the below file:

nano  /etc/sysconfig/network
======================================
NETWORKING=yes
HOSTNAME=ESXTEST1.lab.com
GATEWAY=192.168.0.20
GATEWAYDEV=vswif0
IPV6_AUTOCONF=no
NETWORKING_IPV6=no
======================================
restart the network service for ip change to take effect:

[root@ESXTEST1 sysconfig]# service network restart

 How to edit the  ESX host file ?

nano /etc/hosts

Edit the file to make entry to your host file.
==========================================
127.0.0.1       localhost
::1             localhost
192.168.0.75    ESXTEST1.lab.com ESXTEST1
==========================================

How to edit the DNS entry of your ESX server?

nano /etc/resolv.conf

Edit the file to make changes or to make new entry of dns for your ESX server
========================
nameserver 192.168.0.20
search lab.com
=======================

 what is the command to query the firewall ports ?

esxcfg-firewall – q

How  to open the port in firewall  (port no 8877, tcp, incoming , name: test3 ?

esxcfg-firewall -o 8877,tcp,in,test3