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[MX] How to access backup Routing Engine fxp0 through the static route

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Article ID: KB35557 KB Last Updated: 13 Mar 2020Version: 1.0
Summary:

In some situations, you may need to configure the static route from the management Ethernet interface for management purposes.  If the backup router configuration is not specified, you cannot access the backup Routing Engine (RE).

Symptoms:

There are two Routing Engines on a MX device. RE0 is the backup RE. RE1 is the master RE.

Example configuration:

    re1 {
        interfaces {
            fxp0 {
                unit 0 {
                    family inet {
                        address 10.219.22.158/26;
                    }
                }
            }
        }
        routing-options {
            static {
                route 172.16.0.0/16 next-hop 10.219.22.159;
re0 {                               
        interfaces {
            fxp0 {
                unit 0 {
                    family inet {
                        address 10.219.22.157/26;
                    }
                }
            }
        }
        routing-options {
            static {
                route 172.16.0.0/16 next-hop 10.219.22.159;

In this status, we cannot ping to backup fxp0 10.219.22.157 from 172.16.0.0/16 even though we can see 172.16.0.0/16 in the routing table. However, 172.16.0.0/16 is not in the RE0/backup RE forwarding-table.

user@router-re0# run show route 

172.16.0.0/16      *[Static/5] 2d 01:18:03
                    >  to 10.219.22.159 via fxp0.0
Cause:

This behavior is working as designed. The route with nexthop as private is not synced by GRES. So the route will not be installed in the forwarding table on the backup RE. All routes without interface fxp0, nexthop is private.

Solution:

To reach the destination from backup RE fxp0, configure the backup-router to acquire 'set system backup-router <gateway> destination <prefix>'

On the backup RE, set the configuration as below:

   re0 {                               
        system {
            backup-router 10.219.22.158 destination 172.16.0.0/16;
        }

Then 172.16.0.0/16 will be seen on the forwarding table.

re0# run show route forwarding-table 
172.16.0.0/16      user     0 10.219.22.158      hold      369     2 fxp0.0

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