Static IP route "permanent"

jboogie81

Hey all,

Could someone think of a scenario where someone would want to add the "permanent" syntax to a static route? In Odom's book it says you can do it to force a route into the routing table even when the link is down, but does not explain why you would want to do that and I can't think of a reason.

Thanks in advance for any insight!

kailsar

Say you have an interface that connects to a network, but the connection is unreliable. It is the only route to this network. In this case it might be better to have the route marked as permanent, so that the routing protocol doesn't have to send updates every time the connection goes down and up. The traffic is not getting to the network regardless, as the unreliable route is the only one, so better to have the route permanent and just have the traffic drop when it tries to route over the down link.

That's the only example I can think of, I seem to remember something similar being in the CBTNuggets videos on BGP.

pujan96

Default Route???

mikeybinec

If you shutdown the interface, the routing table will delete/discard the route. Having permanent means the route will still exist in the routing table no matter what happens. So, if a routing protocol crashes, or your ISP changes it's IP address, or _____________________________ (gurus, add a reason here)

Lammle, CCNA ROUTING and SWITCHING GUIDE pg. 358, (c)2013