VMWare Administrator Interview Questions – Part II

Second set of VMWare based interview questions..
Check out our part I, in case if you haven’t:

1. What all should be taken care of while live migrating the VM’s?
A. There are some pre-requisites for VMotion. Please check those here.

2. What are port groups and what are it’s types?
A. Port groups are a kind of templates (though they’re not actually)for creating virtual ports with particular set of specifications. You can create a maximum of 512 port groups on a single host.
VMkernel Port group
Virtual Machine Port group

3. What are VLANs?
A. VLANs provide for logical groupings of stations or switch ports. VLAN or Virtual LAN is used to breakdown the broadcast traffic into many logical groups. Basically, one physical switch comprise of one broadcast domain. VLAN separates one broadcast domain into many small pieces to separate the networks.

4. Name some of the basic commands to troubleshoot connectivity between vSphere Client/vCenter and Esxi server.
A. service mgmt-vmware restart (restarts host agent(vmware-hostd) on VMWare Esxi server)
service vmware-vpxa restart (restarts vCenter agent service)
service network restart (restarts management network on Esxi)

5. What are the security options available for ESXi vSwitch?
A. Promiscuous Mode
MAC Address changes
Forged Transmits

6. What are Promiscuous mode, MAC Address Changes and Forged Transmits?
A. Promiscuous mode: Refer here. Default setting is Reject.
MAC Address Changes: All the virtual machine nics are provided with MAC address at the time of creation and is stored in .VMX file. If the packet doesn’t match with the MAC address, it won’t allow incoming traffic to the VM by setting this option as reject. Default setting is Accept.
Forged Transmits: Same as MAC Address Changes with a small difference: MAC Address Changes works for incoming traffic whereas Forged Transmits works for outgoing traffic. Default setting is Accept.

7. What files makes up the virtual machine?
A. .log – Log file for VMWare tracking each activity.
.nvram – Stores the state of VM Bios.
.vmdk – Virtual disk file, storing all the contents of VM hard drive.
.vmsd – Centralized file for storing information and metadata regarding snapshots.
.vmsn – Stores the state of VM when taking snapshot.
.vmss – Stores the state of a suspended VM.
.vmx – Primary configuration file, storing all the settings related to a VM.

8. How to license an Esxi host?
A. Check here.

9. How to troubleshoot if you find a VM in disconnected state in vCenter?
A. First try pinging the ESXi host to ensure that the host is reachable.
Try logging in to the VMs remotely. This ensures that VMs in the host are working fine.
Try to login to the ESXi host using vSphere client. This is to ensure that the hostd services are running perfectly. If this step fails, restart the hostd service using putty.
If all the three steps did went well, the issue would be with the vpxa or vpxd service. Try restarting the vpxa service in the host and if that didn’t resolve your issue, try restarting vCenter server service.

10. What is NIC teaming?
Mapping a single virtual switch to multiple physical NIC’s is termed as NIC teaming.

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