The permanent Keyword (Optional)

Without the permanent keyword in a static route statement, a static route will be removed

if an interface goes down. A downed interface will cause the directly connected network

and any associated static routes to be removed from the routing table. If the interface comes

back up, the routes are returned.

Adding the permanent keyword to a static route statement will keep the static routes in the

routing table even if the interface goes down and the directly connected networks are

removed. You cannot get to these routes—the interface is down—but the routes remain in

the table. The advantage to this is that when the interface comes back up, the static routes

do not need to be reprocessed and placed back into the routing table, thus saving time

and processing power.

When a static route is added or deleted, this route, along with all other static routes, is

processed in one second. Before Cisco IOS Software Release 12.0, this processing time was

five seconds.

The routing table processes static routes every minute to install or remove static routes

according to the changing routing table.

To specify that the route will not be removed, even if the interface shuts down, enter the

following command, for example:

Router(config)#ip route 172.16.20.0 255.255.255.0 172.16.10.2

permanent