VMWare interview questions and answers -Networking

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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

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8 Responses

  1. Suman
    Suman at |

    Thanks. Its very helpfull

    Reply
  2. Mohammed Raffic
    Mohammed Raffic at |

    Thanks Suman….Will try to contribute my best as much as possible

    Reply
  3. Saran Raj
    Saran Raj at |

    Excellant work Raffic, expecting more from u

    Reply
  4. Mohammed Raffic
    Mohammed Raffic at |

    Thanks…Saran… sure definetly will try to meet your expectation by posting lot of quality contents

    Reply
  5. Ickram
    Ickram at |

    Hi,

    It might be worth mentioning that ESXi console is Free Busybox Console in Tech Support Mode.
    As ESXi is the standard Hypervisor from Vmware.

    Reply
  6. Umesh
    Umesh at |

    Hello,

    Nice, Expecting more deeply.

    Reply
  7. Vikram
    Vikram at |

    Nice job Mohammed. try to post important configuration maximums related to networking in ESX and few other. make it more expert level(updates, vm bkp,…).

    Kindly share the link if you update any blogs.

    good job done! Keep it up

    Reply
  8. Kaja
    Kaja at |

    Nice work Raffic !!! thanks

    Reply

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