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Yugandhar's avatar
Yugandhar
Icon for Nimbostratus rankNimbostratus
Nov 02, 2018

Reg MAC Address for a Virtual Server.

Hi,

 

Would like to know how a MAC address is assigned to a Virtual Server in active-standby setup, as I observe multiple virtual servers with in the same vlan share same MAC address.

 

Below is the output of "sh ip arp" from

 

192.168.52.14 00:13:35 9ece.25ec.e61a Vlan1001

 

192.168.52.15 00:01:06 9ece.25ec.e61a Vlan1001

 

192.168.52.16 00:00:59 9ece.25ec.e61a Vlan1001

 

192.168.52.17 00:00:52 9ece.25ec.e61a Vlan1001

 

192.168.52.18 00:14:00 ce89.9bd1.200a Vlan1001

 

192.168.52.19 00:00:41 ce89.9bd1.200a Vlan1001

 

192.168.52.20 00:00:35 ce89.9bd1.200a Vlan1001

 

192.168.52.21 00:01:28 ce89.9bd1.200a Vlan1001

 

192.168.52.110 00:00:26 0050.56b7.066e Vlan1001

 

192.168.52.111 00:00:26 0050.56b7.066e Vlan1001

 

192.168.52.112 00:00:26 0050.56b7.066e Vlan1001

 

192.168.52.113 00:00:26 0050.56b7.066e Vlan1001

 

192.168.52.114 00:00:26 0050.56b7.066e Vlan1001

 

==========

 

In a active standby unit, Why the MAC address of a Self IP (Non floating) is same ?.

 

172.27.160.3 00:08:09 0050.56b7.066e Vlan120

 

172.27.160.4 00:08:09 0050.56b7.066e Vlan120

 

172.27.160.5 00:06:34 0050.56b7.0eff Vlan120

 

172.27.160.21 00:08:09 0050.56b7.066e Vlan120

 

172.27.160.30 00:14:29 9ece.2a2c.9c0b Vlan160

 

172.27.160.31 00:14:38 ce89.92e9.890a Vlan160

 

Thanks,

 

Yugandhar.

 

application delivery
BIG-IP
LTM

1 Reply

  • Simon_Blakely's avatar
    Simon_Blakely
    Icon for Employee rankEmployee
    Nov 04, 2018

    Each LTM has a physical Mac address that is used for virtual addresses and self-IP addresses that are active on the device.

     

    So you will see that all the mac addresses will be the same.

     

    K14513: MAC address assignment for interfaces, trunks, and VLANs (11.x - 12.x)

     

    After a failover, the new active LTM will send Gratuitous ARPs with it's own mac address for all the virtual addresses that are now active.

     

    You can configure Mac Masquerading, where an artificially generated Mac Address is used for virtual addresses and floating Self-IPs. After failover, the new active Device starts responding to the configured Mac Address. This can be faster, but relies on the switch CAM table updating correctly.

     

    K13502: Configuring MAC masquerade (11.x - 14.x)