Description

This article explains a common issue encountered in chassis cluster setups where the management interface (fxp) of the secondary node is not reachable, despite backup router configuration being present.

Symptoms

  • Secondary node fxp interface is not reachable over the network.
  • Connectivity issues occur even though a backup-router configuration is defined.
  • Expected routes are missing from the forwarding table.

Note: In a cluster setup, the secondary node only maintains the forwarding table, not the full routing table.

Solution

The issue can occur if the backup router IP address is not in the same subnet as the fxp interface.

In such cases:

  • The next-hop becomes unreachable
  • Routes associated with the backup router are not installed in the forwarding table
  • Traffic destined for configured networks fails

In below example the backup router ip address is out of the subnet range which is configured in fxp0 interface:

set groups node1 system host-name node1
set groups node1 system backup-router 10.10.20.1
set groups node1 system backup-router destination 192.168.0.0/24
set groups node1 interfaces fxp0 unit 0 family inet address 10.10.10.1/29

Hence the routes for 192.168.0.0/24 is not installed on the device:

root@SRX# run show route forwarding-table destination 192.168.0.0
Routing table: default.inet
Internet:
Destination        Type RtRef Next hop           Type Index    NhRef Netif
default            user     0                    dead      331     2
default            perm     0                    rjct       36     1

 

Solution:
Set the backup router on the same subnet as your FXP, this would install the routes on the forwarding table

Once the next hop is reachable the routes wil get installed and output will be as below:

root@SRX# run show route forwarding-table destination 192.168.0.0 
Routing table: default.inet
Internet:
Destination        Type RtRef Next hop           Type Index    NhRef Netif
192.168.0.0/24     user     0 10.10.10.110        ucst      327     2 fxp0.0

Modification History

2023-10-10 : Article Created