Understanding Static Route Control in Routing and Forwarding Tables

You can control the importation of static routes into the routing and forwarding tables in a number of ways. Primary ways include assigning one or more of the following attributes to the route:

• retain—Keeps the route in the forwarding table after the routing process shuts down or the device reboots.
• no-readvertise—Prevents the route from being readvertised to other routing protocols.
• passive—Rejects traffic destined for the route.

This topic includes the following sections:

• Route Retention
• Readvertisement Prevention
• Forced Rejection of Passive Route Traffic

Route Retention

By default, static routes are not retained in the forwarding table when the routing process shuts down. When the routing process starts up again, any routes configured as static routes must be added to the forwarding table again. To avoid this latency, routes can be flagged as retain, so that they are kept in the forwarding table even after the routing process shuts down. Retention ensures that the routes are always in the forwarding table, even immediately after a system reboot.

Readvertisement Prevention

Static routes are eligible for readvertisement by other routing protocols by default. In a stub area where you might not want to readvertise these static routes under any circumstances, you can flag the static routes as no-readvertise.

Forced Rejection of Passive Route Traffic

Generally, only active routes are included in the routing and forwarding tables. If a static route's next-hop address is unreachable, the route is marked passive, and it is not included in the routing or forwarding tables. To force a route to be included in the routing tables regardless of next-hop reachability, you can flag the route as passive. If a route is flagged passive and its next-hop address is unreachable, the route is included in the routing table and all traffic destined for the route is rejected.

Related Topics

• Junos OS Feature Support Reference for SRX Series and J Series Devices
• Example: Controlling Static Routes in Routing and Forwarding Tables