Floating Static Routes

[Chris Pohlad-Thomas]

I was curious if there are any conditions in which a static route will drop from the routing table.

Here is my situation. We have a PTP and a VPN connection from one of our remote offices to this office. Right now, the static routes to this office all go down the PTP. I wanted to setup a floating static route to route them out our GRE tunnel (which passes through the VPN tunnel) in case the PTP goes down (or we manually bring it down).

Will this ever work or do static routes never leave the routing table? If I manually bring down the serial port which the original static route points to, will that remove it from the table if there is another static route with an AD one higher than the existing static route?         

[Richard Burts · Accepted solution]

Chris

Yes there are conditions in which a static route will be removed from the routing table. If the static route just points to an interface and the interface that the static route uses changes the line protocol from up to down then the static route is removed from the routing table. This is common on interfaces like serial with HDLC or PPP and not common on interfaces like Ethernet.

Also if the static route specifies a next hop address, if the interface toward that next hop line protocol changes from up to down and there is not another interface that has a route to the next hop then the static route will be removed.

If the static route uses Ethernet it is fairly common to use tracking or IP SLA (depending on version of IOS) to remove the static route if connectivity to the next hop is lost but the interface stays up.

HTH

Rick

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