router switching problem

Unanswered Question
May 13th, 2008

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.



I have this problem too.
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mahmoodmkl Wed, 05/14/2008 - 00:14


Instead of static routes why dnot u use any routing protocol which will give u faster convergence.



sirdudesly Wed, 05/14/2008 - 01:14

use a routing protocol with weighted metrics to set your preferences if a link fails

sdoremus33 Thu, 05/15/2008 - 14:50

As the other members mentioned simply use a Link state routing protocol and adjust metrics and timers to perform the same as what your doiung just alot easier

Tony.henry Sun, 05/18/2008 - 15:45


Whilst I generally agree that a routing protocol will make life easier for you. You'll have to be carefull in implementing it in your situation due to your VSAT interfaces being ethernet. They will appear to be more attractive to routing protocols which take bandwidth into accound then your serial links. which won't meet your requirements of having the VSAT as a service of last resort.

I must say that I'm at a bit of a loss why your routers are taking so long to converge. To be honest I'm not really aware what timers and static routes have to do with each other. I've read the documentation, I just don't get it.

In my experience, All three routes should be visible in your "sho Ip route" with leased line first with lowest AD, the route will fall out of the route table as soon as the link is gone, and come back when the link is restored.

Are the alternate links on demand or are they permantly available?




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