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Floating static route timeout

How long does it take for a floating static route to be initiated into the routing table when an interface goes down?

Thank you.

Everyone's tags (3)
2 ACCEPTED SOLUTIONS

Accepted Solutions
Hall of Fame Super Blue

Re: Floating static route timeout

lkadlik wrote:

How long does it take for a floating static route to be initiated into the routing table when an interface goes down?

Thank you.

It's not so much when the interface goes down as when the route is removed from the routing table. So as soon as the original route is removed the floating static should then be installed.

Edit - however bear in mind that different interfaces react differently eg -

R1 (s0/0) -> (s0/0) R2

if you have the floating static on R1 and s0/0 on R2 goes down it should be fairly instantaneous

R1 (fa0/0) -> L2 switch -> (fa0/0) R2

if fa0/0 on R2 or the port on the L2 switch connected to fa0/0 on R2 goes down fa0/0 on R1 stays up because it's connection to the L2 switch is fine. So the floating static would never be used. For this kind of setup you would need to use IP SLA to track the remote interface ie. fa0/0 on R2 to check if it is reachable and if it stops responding IP SLA will then remove the original route on R1 and the floating static would then be installed.

Jon

Hall of Fame Super Blue

Re: Floating static route timeout

lkadlik wrote:

Thank you.  I think my better question would now be how long does it take a static route to be removed from the routing table if the interface that it uses goes down?

Should be fairly instantaneous although to be honest i've never actually timed it. Again the same proviso's apply. If you are talking about an interface on the actual router where the static route is configured then it should like i say be almost immediate.

Jon

4 REPLIES
Hall of Fame Super Blue

Re: Floating static route timeout

lkadlik wrote:

How long does it take for a floating static route to be initiated into the routing table when an interface goes down?

Thank you.

It's not so much when the interface goes down as when the route is removed from the routing table. So as soon as the original route is removed the floating static should then be installed.

Edit - however bear in mind that different interfaces react differently eg -

R1 (s0/0) -> (s0/0) R2

if you have the floating static on R1 and s0/0 on R2 goes down it should be fairly instantaneous

R1 (fa0/0) -> L2 switch -> (fa0/0) R2

if fa0/0 on R2 or the port on the L2 switch connected to fa0/0 on R2 goes down fa0/0 on R1 stays up because it's connection to the L2 switch is fine. So the floating static would never be used. For this kind of setup you would need to use IP SLA to track the remote interface ie. fa0/0 on R2 to check if it is reachable and if it stops responding IP SLA will then remove the original route on R1 and the floating static would then be installed.

Jon

New Member

Re: Floating static route timeout

Thank you.  I think my better question would now be how long does it take a static route to be removed from the routing table if the interface that it uses goes down?

Hall of Fame Super Blue

Re: Floating static route timeout

lkadlik wrote:

Thank you.  I think my better question would now be how long does it take a static route to be removed from the routing table if the interface that it uses goes down?

Should be fairly instantaneous although to be honest i've never actually timed it. Again the same proviso's apply. If you are talking about an interface on the actual router where the static route is configured then it should like i say be almost immediate.

Jon

Cisco Employee

Re: Floating static route timeout

There is a difference in static route insertion behavior between releases prior to 15.0M and 15.0M onwards. Previously the route insertion was based on a polling timer but now it is event driven. So prior to 15.0M you could see as much as 60 second delay between an interface transition and a floating route insertion in RIB. I believe there was a command to modify this but I dont recall the exact syntax off the top of my head.

Atif

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