VMWare Top Interview Questions with Answers Part 2

Difference between Standard and Distributed Switch.

Features	Standard Switch	Distributed Switch
Management	Standard switch needs to managed at each individual host level	Provides centralized management and  monitoring of the network configuration  of all the ESXi hosts that are associated with the dvswitch.
Licensing	Standard Switch is available for all  Licensing Edition	Distributed switch is only available for enterprise edition of licensing
Creation & configuration	Standard switch can be created and  configured at ESX/ESXi host level	Distributed switch can be created and configured  at the vCenter server level
Layer 2 Switch	Yes, can forward Layer 2 frames	Yes, can forward Layer 2 frames
VLAN segmentation	Yes	Yes
802.1Q tagging	Can use and understand 802.1q VLAN tagging	Can use and understand 802.1q VLAN tagging
NIC teaming	Yes, can utilize multiple uplink to  form NIC teaming	Yes, can utilize multiple uplink to form  NIC teaming
Outbound Traffic Shaping	Can be achieved using standard switch	Can be achieved using distributed switch
Inbound Traffic Shaping	Not available as part of standard switches	Only possible at distributed switch
VM port blocking	Not available as part of standard  switches	Only possible at distributed switch
Private VLAN	Not available	PVLAN can be created as part of dvswitch. 3 types of PVLAN(Promiscuous, Community and Isolated)
Load based Teaming	Not available	Can be achieved using distributed switch
Network vMotion	Not available	Can be achieved using distributed switch
Per Port policy setting	Policy can be applied at switch and port group	Policy can be applied at switch, port group and even per port level
NetFlow	Not available	Yes
Port Mirroring	Not available	Yes

Q1. Virtual Machine is not manageable / connectable after successful vMotion. what is the reason ?

 2. A company has 2 ESXi hosts, if one of the ESXi host goes down, the VMs from the failed ESXi host is not moving to the live ESXi host. What may be the reasons.

Ans: First try to ping the management IP from one host to another host. Login on esxi through putty

Type ping server(IP or name).

Check out the NIC configuration. May be nic is not connected.

2. Sufficient resource are available to run the vm.

Q2.vcenter goes down , what are the feature will not work ?

·         A. HA will still work if it’s been configured vcenter is not required for HA to function, only required to configure HA.

DRS requires vmotion which is a vcenter function so it will stop functioning

FT I m not 100% but i believe it’s the same as HA once configured through vcenter it will still function if vcenter was to go down. The primary and secondary vm exchange heartbeats to make sure both are available and if not then it fails over without the need of vcenter. but if vcenter is unavailable and FT has failed to the secondary i believe you will need vcenter up and available to set it back up.

Q3. Storage DRS

A. Storage DRS allows you to manage the aggregated resources of a datastore cluster. When Storage DRS is enabled, it provides recommendations for virtual machine disk placement and migration to balance space and I/O resources across the datastores in the datastore cluster.

When you enable Storage DRS, you enable the following functions

1.Space load balancing among Datastore within a Datastore cluster

2.I/O load balancing among Datastore within a Datastore cluster.

3.Initial placement for virtual disks based on space and I/O workload.

Q4 one ESXi goes down or disconnected. How will you troubleshoot?

A.    First try to access the ESXi through vSphere client, if accessible then try to reconnect from vCentre.

B.    Try to access the KVM console from CIMC. If console is working fine try to restart the Management service.

C.    If showing purple screen take reboot.

Q5. Hard disk space increase option is not highlighting, what will you do?

A.    It might be possible due to its hard disk locked at the time of snapshot creation. It’s locked the hard disk at the time of snapshot creation, A snapshot is the point in time image which create an image of current hard disk.

B.  Its create a new disk file named as original disk name -1 and all the changes will be made in new disk file, at the end it consolidate the file and create the new file with the original name.

Q6. Type of port group.

A.    Virtual port group.

B.    Kernel port group.

VPXD-It is Vcenter Server Service. If this service is stopped then we will not able to connect to Vcenter Server via Vsphere client.

VPXA-It is the agent of Vcenter server also known as mini vcenter server which is installed on the each esx server which is managed by Vcenter server. What are the management actions we are performing on top of the vcenter server. (Like:- Increasing/Decreasing RAM & HDD, Making any type of changes in cluster,

Doing vmotion. This agent collects all information from the vcenter server and pass this information to the kernal of the esx server.

HOSTD- This is the agent of ESX server, here VPXA pass the information to the HOSTD and hostd pass the information to ESX server.

There are two ways you can restart the management agents. The simply way is from the console of ESXi, log in, and restart this via the options available within the menus available.

If you have SSH enabled on your ESXi server these services can also be restarted by running the following from the console command line:

Restarts the management agent

/etc/init.d/hostd restart

Restarts the vpxa service

/etc/init.d/vpxa restart

NetFlow

is a network analysis tool that you can use to monitor network monitoring and virtual machine traffic. NetFlow is available on a vSphere Distributed Switch version 5.0.0 and later.

Port Mirroring.

Difference between WWN and WWPN?

A WWPN (world wide port name) is the unique identifier for a fibre channel port where a  WWN (world wide name) the unique identifier for the node itself.

A good example is a dual port HBA.  There will be two WWPN's (one for each port) and only a single WWN for the card itself.

Logical Unit Number Masking or LUN masking

Logical Unit Number Masking or LUN masking is an authorization process that makes a Logical Unit Number available to some hosts and unavailable to other hosts. LUN masking is mainly implemented at the host bus adapter (HBA) level.

Multipathing is a technique that lets you use more than one physical path that transfers data between the host and an external storage device. In case of a failure of any element in the SAN network, such as an adapter, switch, or cable, ESXi can switch to another physical path, which does not use the failed component.

Most Recently Used (MRU): The VMW_PSP_MRU policy selects the first working path, discovered at system boot time. If this path becomes unavailable, the ESXi/ESX host switches to an alternative path and continues to use the new path while it is available. This is the default policy for Logical Unit Numbers (LUNs) presented from an Active/Passive array. ESXi/ESX does not return to the previous path if, or when, it returns; it remains on the working path until it, for any reason, fails.

Note: The preferred flag, while sometimes visible, is not applicable to the MRU pathing policy and can be disregarded.

•Fixed (Fixed): The VMW_PSP_FIXED policy uses the designated preferred path flag, if it is configured. Otherwise, it uses the first working path discovered at system boot time. If the ESXi/ESX host cannot use the preferred path or it becomes unavailable, the ESXi/ESX host selects an alternative available path. The host automatically returns to the previously defined preferred path as soon as it becomes available again. This is the default policy for LUNs presented from an Active/Active storage array.

•Round Robin (RR): The VMW_PSP_RR policy uses an automatic path selection, rotating through all available paths, enabling the distribution of load across the configured paths.

◦For Active/Passive storage arrays, only the paths to the active controller will be used in the Round Robin policy.

◦For Active/Active storage arrays, all paths will be used in the Round Robin policy.

Note: For logical units associated with Microsoft Cluster Service (MSCS) and Microsoft Failover Clustering virtual machines, the Round Robin pathing policy is supported only on ESXi 5.5 and later.

•Fixed path with Array Preference: The VMW_PSP_FIXED_AP policy was introduced in ESXi/ESX 4.1. It works for both Active/Active and Active/Passive storage arrays that support Asymmetric Logical Unit Access (ALUA). This policy queries the storage array for the preferred path based on the array's preference. If no preferred path is specified by the user, the storage array selects the preferred path based on specific criteria.

Q. What is Vmkernel ?

 

Ans. The VMkernel is the liaison between virtual machines (VMs) and the physical hardware that supports them. VMware calls VMkernel a microkernel because it runs on bare metal,directly on VMware ESX hosts. The VMkernal is responsible for allocating memory, scheduling CPUs and providing other hardware abstraction and operating system (OS) services.

Q. Maximum Distributed switches per vCenter in 5.1 and 5.5

Ans. 128

Q. Delete all and consolidation process in Snapshot.

Ans. In Delete all option Merge all delta.vmdk with original vmdk file.

         In consolidation process Merge all delta.vmdk with original vmdk then create new delta.vmdk

         Ex:- 001_.vmdk + 002_vmdk + .vmdk  = 003_vmdk

Q. How to add the RDM on second VM (sharing mode).

Q. ESXi partitions & logs,

How to check the esxi logs from browser.

~ # cd /var/run/log

ls -ltrh

ls -ltrh | grep vmkernel

/vmfs/volumes/536d917d-7eee079c-b425-f84f577263e2/log # ls –lrth

/vmfs/volumes/536d917d-7eee079c-b425-f84f577263e2/log # ls -lrth |  grep vmk

/vmfs/volumes/536d917d-7eee079c-b425-f84f577263e2/log # ls -lrth |  grep vmkernel.4.gz

Through browser…

https://10.X.X.X/host (will show all the logs)

Logs time will be shown in UTC (Coordinated Universal Time (UTC).

VM files during power off and power on.

Firewall of ESXi?