VMware Interview Questions and answers -Networking Section
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 vmware and 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. This is one of the frequently asked VMware interview questions.
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
VMware Interview Questions – Network Security
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 VLAN tagging
What are the Traffic Shaping policies available in the vSwitch?
Understanding the usecases of Traffic shaping policies are very important part of VMware interview questions. 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.
VMware Interview Questions – Network Command Line
Being an VMware administrator, good knowledge about ESX and ESXi commands is must. This part of VMWare interview questions covers various commands related to networking concepts of VMware.
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.
VMware Interview Questions – vSwitch
Below list of VMware Interview questions help you to understand difference between vSwitch and Distributed switch and various commands to get information about vSwitch.
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.
=========================================================================
VMware Interview Questions – Edit Configuration Files
It is also important to understand various configuration files to configure various service like DNS & NTP. Below VMware interview questions helps you to understand how to edit various configuration files.
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
I hope this VMware interview questions for networking will be helpful to you during your VMware interview preparation. If you are looking for more VMware interview questions ,Please visit my Interview Questions section. Thanks for reading!!!. Be social and share it in social media like Google+, facebook and twitter.