[c-nsp] Static routes in routing table

[Rodney Dunn]

On Thu, Oct 06, 2005 at 05:34:36PM -0700, Chen, Qinxue wrote:
> We have two static routes to the same destination through two different next-hops. One static route has less prefered admin distance. We want a graceful failover happening when the primary static route fails. Now the question is how soon can Cisco routers take out the failed static route.

We don't yet have BFD integration with static routes so you have
to rely on some notification such as IP SLA with an object tracking to
declare it down.

 If the next hop is on a direct-connected network (not necessaryly a point-to-point link,) that will depend on how soon the ARP table cleared on the Cisco router.

No it's not based on ARP. It's based on a recursive route to the next hop.

 There are two cases:
> 
> 1) If cisco router -> next-hop is a point-to-point link, will the Cisco router flash the ARP entry for the next-hop right after the next-hop is down?

We don't support p2p ethernet so no. If you pull the cable the interface
will come down and the route will come out if you point the route at
the interface/next hop combo.

We used to adjust the statics on a 60 second timer but you can tune that
now down to 1 sec:

UUT_(config)#ip route static adjust-time ?
  <1-60>  Adjustment time in seconds


> 2) If the next-hop is connected to a cisco switch but on a direct-connected network as the Cisco router, will the Cisco router has to wait for the ARP timeout for the next hop to take out the failed static route? Or any other way to make it instantly.
>

As before it's not based on arp. It's based on a route to the next hop being
there. If you want to verify that path is up you need to look at static
routes with object tracking on CCO.

If you want BFD integration with object tracking for faster convergence
open a TAC case and ask them to attach it to:

CSCsb48249
Externally found enhancement defect: New (N)
Request for BFD integration with object tracking

Rodney

 
> Thanks
> 
> -Qinxue
> 
> -----Original Message-----
> From: Rodney Dunn [mailto:rodunn at cisco.com]
> Sent: Thursday, October 06, 2005 12:21 PM
> To: Chen, Qinxue
> Cc: cisco-nsp at puck.nether.net
> Subject: Re: [c-nsp] Static routes in routing table
> 
> 
> On Thu, Oct 06, 2005 at 12:12:21PM -0700, Chen, Qinxue wrote:
> > I get a quick question:
> > 
> > If next-hop for a static route is unreachable, will Cisco routers put in the routing table? (What about Junipers?) Thanks
> >
> 
> For Cisco.
> 
> Not unless the next hop recurses through a route that is up.
> 
> That's assuming you don't point at the interface and next hop or
> you are not doing some form of object tracking.