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[ScreenOS] Firewall cannot recognize peer device in NSRP cluster



Article ID: KB14055 KB Last Updated: 17 Dec 2013Version: 5.0

The firewall device cannot recognize its peer device in an NSRP cluster. Two solutions are offered.


The devices cannot recognize each other in an NSRP cluster.  Both devices are Primary, so the firewalls are in a 'split-brain' state.

The command debug nsrp all on both devices reports the following output:

"diff version(0), drop it" on firewall A
"diff version(3), drop it" on firewall B



The firewall has a limitation on nsrp-max-cluster and nsrp-max-vsd environment variables.  All devices in one broadcast domain should be set with same values to have NSRP communication between the devices.

In addition, in one broadcast domain, devices cannot have some devices in traditional mode (cluster 8 and VSD 8) and other devices using the NSRP environment variable. 
For example:

FW_A(M)-> get envar
nsrp-max-cluster=64               <- Firewall A has NSRP max cluster configured
run_image=default (screenos_image)

FW_B(M)-> get envar

For more information on the NSRP environment variables, refer to KB11150 - Virtual MAC (VMAC) address for HA pair when using nsrp-max-cluster and nsrp-max-vsd variables or the Concepts & Examples ScreenOS Reference Guide - Volume 11 - High Availability.

There are two solutions for this issue, but only one of them can be used:

Solution 1:  On firewall B

set envar nsrp-max-cluster=64

In real time, the above problem is more likely to be encountered in a situation where one of the NSRP Cluster members was replaced (RMAed). After putting in the replacement device, physical connectivity was done, required licenses/old working configuration was loaded, however devices are still not able to see each other in NSRP cluster. The reason is that when you copy the old configuration, envar variables do not get copied, as they are not part of the configuration .So, you have to explicitly set the envar variables on the replaced device as in the case above .

Solution 2:  On firewall A

unset envar nsrp-max-cluster

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