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Router switching problem

Dear experts,

Aim: To enable router to shift to next available route to a destination within 5 seconds. i.e to converge faster (within 5 seconds)

The priority of links is

1. Leased Line modem


3. VSAT ( satellite modem)

The ip routes are configured in router A is shown below

ip route static adjust-time 2

ip route 5

ip route 10

ip route 15

The ip routes are configured in router B is shown below

ip route static adjust-time 2

ip route 5

ip route 10

ip route 15

The last parameter indicate the Metric value of the AD value for the route.

ip route static adjust-time 2

The default value is 60 seconds.

Since we wanted to decrease the time for the routes to converge we set the value to 2 seconds, but the router is consuming 30 seconds for the changeover compared to the earlier 45-60 seconds.

What are alternate methods to decrease the changeover time?

What is the limitation of cisco 2821 router for fast changeover?

Are higher end routers capable of faster changeover ?if yes how fast?

What is the current technology limitation?

Plz give me the information plz and iam attaching the diagram.




Re: Router switching problem

It really depends not on how quickly the router can switch to the alternate route. With layer-3 routing protocols, it is now possible to converge in sub-second times.

Rather, it depends mostly on how quickly the router can detect that the next-hop is down. Now, if you can persuade the interface leading to to go down as soon as the next-hop is unavailable, then convergence would be near instantaneous. If, however, it does not go down immediately, then you will need to do some next-hop tracking. It is the parameters of the next-hop tracking that will determine your convergence time ratyer than any static adjust time.

If you have a very recent version of IOS, you might like to consider BFD (Bi-directional Forwarding Detection) together with a routing protocol. That can bring the convergence time down to sub-second levels.

Kevin Dorrell


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