VMWare Top Interview Questions with Answers
1) Explain about your production environment? How many cluster’s, ESX, Data Centers, H/w etc ?
2) How does VMotion works? What’s the port number used for it?
ANS–> TCP port 8000

3) Prerequisites for VMotion?
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

4) How does HA works? Port number? How many host failure allowed and why?
ANS–> Maximum allowed host failures within a HA cluster is 4. What happens if 4 hosts have failed and a 5th one also fails.
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

5) What are active host / primary host in HA? Explain it?
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.

6) Prerequisites for HA ?
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.

7) How do DRS works? Which technology used? What are the priority counts to migrate the VM’s?
8) How does snap shot’s works?
9) What are the files will be created while creating a VM and after powering on the VM?
10) If the VMDK header file corrupt what will happen? How do you troubleshoot?
11) Prerequisites VC, Update manager?
12) Have you ever patched the ESX host? What are the steps involved in that?
13) 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?
14) 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?
15) How will you turn start / stop a VM through command prompt?
16) I have upgraded a VM from 4 to 8 GB RAM; it’s getting failed at 90% of powering on? How do you troubleshoot?
17) 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)?
18) I want to add a new VLAN to the production network? What are the steps involved in that? And how do you enable it?
19) Explain about VCB? What it the minimum priority (*) to consolidate a machine?
20) How VDR works?
21) What’s the difference between Top and ESXTOP command?
22) How will you check the network bandwidth utilization in an ESXS host through command prompt?
23) How will you generate a report for list of ESX, VM’s, RAM and CPU used in your Vsphere environment?
24) 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?
25) How does FT works? Prerequisites? Port used?
26) Can I VMotion between 2 different data centers? Why?
27) Can I deploy a VM by template in different data centers ?
28) 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?
29) Which port number used while 2 ESX transfer the data in between?
30) Unable to connect to a VC through Vsphere client? What could be the reason? How do you troubleshoot?
31) Have you ever upgraded the ESX 3.5 to 4.0? How did you do it?
32) What are the Vsphere 4.0, VC 4.0, ESX 4.0, VM 7.0 special features?
33) What is AAM? Where is it used? How do you start or stop through command prompt?
ANS) VMware-aam = HA.
VMware purchased the HA technology from Legato, who originally coined it as “Automated Availability Manager”.

34) Have you ever called VMWare support? Etc

35) Explain about Vsphere Licensing? License server?

36) How will you change the service console IP?
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*

•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).

37) What’s the difference between ESX and ESXi?
38) What’s the difference between ESX 3.5 and ESX 4.0?

39) 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%\vmware-temp\vmware-converter* (in Windows NT)
Client logs:

Send these in to support using File > Export Logs. For Converter Boot CD, map a network drive using the
network configuration tool (see Chapter 5, “Using the Converter Boot CD for Local Cold Cloning,” on page 37)
and use File > Export Logs.

40) Micro vMotion

One thought on “Some Basic Interview Questions and Answers : Part 1

  1. Desi Williams

    IT is really such a great information .. and please correct on 4)ESX Servers muct(must) have consistent Networks and Netbooks labels

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