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Virtual MAC (VMAC) address for HA pair when using nsrp-max-cluster and nsrp-max-vsd variables



Article ID: KB11150 KB Last Updated: 17 Dec 2012Version: 5.0
What is the VMAC address when using nsrp-max-cluster and nsrp-max-vsd variables,  Enhanced Range of Cluster IDs and VSD IDs?
In ScreenOS 6.1, the number of Cluster IDs and Virtual Security Device (VSD) IDs can be increased up to 64.
Previous releases supported up to 7 NSRP clusters, and each NSRP cluster supported up to 8 VSD groups.

After increasing the number of Cluster IDs or Virtual Security Device (VSD) IDs, the VMAC address will change.
To enable NSRP enhancements:

set envar nsrp-max-cluster=<num 1>                  <--  Number of NSRP clusters
set envar nsrp-max-vsd=<num 2>                      <--  Number of VSD groups
save, reset                                         <--  Device needs to be rebooted for the environment variable take effect.

The variables nsrp-max-cluster and nsrp-max-vsd can take values between 0 and 64 and its product should not exceed 512.

The VMAC address for the shared interface of an HA pair has the following format after configuring NSRP enhancement variables:  

0010 db 1111110X XXXXXXXX NNNNNNNN
XXXXXXXXX (9-bit) is for NSRP cluster id and VSD group id
NNNNNNNN (8-bit) is for interface number

set nsrp cluster id 30  --> 30=11110
set envar nsrp-max-cluster=32
set envar nsrp-max-vsd=16

nsrp-max-cluster=32 = 2^5 --> 5 bits used for NSRP cluster id
nsrp-max-vsd=16 = 2^4 --> 4 bits used for VSD group id

SSG520(M)-> get int e0/2
Interface ethernet0/2:
  description ethernet0/2
  number 6, if_info 393120, if_index 0, mode nat
6=0000 0110

Therefore, the VMAC addresses for VSD group 1, 3, 8, 9 and 15 are:

eth0/2:1     0010 db 11111101 1110 0001 0000 0110    = 0010.dbfd.e106
eth0/2:3     0010 db 11111101 1110 0011 0000 0110    = 0010.dbfd.e306
:8     0010 db 11111101 1110 1000 0000 0110    = 0010.dbfd.e806
:9     0010 db 11111101 1110 1001 0000 0110    = 0010.dbfd.e906
:15   0010 db 11111101 1110 1111 0000 0110    = 0010.dbfd.ef06

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