Chapter 9 High Availability for FortiOS 5.0 : An introduction to the FGCP : Identifying the cluster and cluster units : Group ID
  
Group ID
Similar to the group name, the group ID is also identifies the cluster. In most cases you do not have to change the group ID. However, you should change the group ID if you have more than one cluster on the same network. All members of the HA cluster must have the same group ID. The group ID is a number from 0 to 255.
Changing the group ID changes the cluster virtual MAC address. See “Cluster virtual MAC addresses”.
Enter the following CLI command to change the group ID to 10:
config system ha
set group-id 10
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