Configuring backup router

Backup Router

When a router or switch is booting, the routing protocol process (rpd) is not running; therefore, the router or switch has no static or default routes. To allow the router or switch to boot and to ensure that the router or switch is reachable over the network if the routing protocol process fails to start properly, you configure a backup router (running IP version 4 [IPv4] or IP version 6 [IPv6]), which is a router that is directly connected to the local router or switch (that is, on the same subnet).

To achieve network reachability while loading, configuring, and recovering the router or switch, but without the risk of installing a default route in the forwarding table, include the destination option. Specify the address in the format network/mask-length so that the entire network is reachable through the backup router.

By default, all hosts (default route) are reachable through the backup router. To eliminate the risk of installing a default route in the forwarding table, include the destination option, specifying an address that is reachable through the backup router. Specify the address in the format network/mask-length so that the entire network is reachable through the backup router.

Note: The routes 0.0.0.0/0 or ::/0 should not be used as a destination address in the backup router configuration. You must include a proper subnet range of /8 or higher in the destination address.

When the routing protocols start, the address of the backup router is removed from the local routing and forwarding tables. To have the address remain in these tables, configure a static route for that address by including the static statement at the [edit routing-options] hierarchy level.Back

Configuring a Backup Router Running IPv4

To configure a backup router running IPv4, include the backup-router statement at the [edit system] hierarchy level:

[edit system]backup-router address <destination destination-address>;

The following example shows how to configure a backup router running IPv4 and have its address remain in the routing and forwarding tables:

Note: The Routing Engine on the backup router only supports 16 destinations addresses. If you configure more than 16 destination addresses, the Junos OS ignores destination addresses after the sixteenth address and displays a commit-time warning message to this effect.

[edit]system {backup-router 192.168.1.254 destination 208.197.1.0/24;}routing-options {static {route 208.197.1.0/24 {next-hop 192.168.1.254;retain;}}}

To configure a backup router running IPv4:

1. Include the backup-router statement at the [edit system] hierarchy level.
   [edit groups group-name system]backup-router address <destination destination-address>;
   For example:
   [edit groups re0 system]backup-router 192.168.1.254 destination 172.16.1.0/24;
   [edit groups re1 system]backup-router 192.168.1.254 destination 172.16.1.0/24;
2. (Optional) Configure a static route to the management network.
   Junos OS only uses the backup router during the boot sequence. If you want to configure a backup router for use after startup, you can set up a static route. The static route goes into effect when the routing protocol process is running.
   routing-options {static {route 172.16.1.0/24 {next-hop 192.168.1.254;retain;}}}
3. If you used one or more configuration groups, apply the configuration groups, substituting the appropriate group names.
   For example:
   [edit]user@host# set apply-groups [re0 re1]
4. Commit the changes:
   [edit]root@# commit