Cisco Support Community
Community Member

IGRP AS Question

Hi i'm Farely new to cisco scene and am learning from scratch, so forgive me if this sounds really dump. When you are configuring IGRP and you have one set of routers on one AS and another set of routers on another AS and you want to be able to get from one AS to another, do you just simply configure both AS networks on your "gateway" routers???

Hall of Fame Super Bronze

Re: IGRP AS Question

Placing both ASes in the gateway routers is a feasible solution.

Hall of Fame Super Gold

Re: IGRP AS Question

I would make the point that putting both ASes on the same gateway router may be part of the solution, but by itself is not likely to produce the desired results. For an example lets assume that we have one group of routers in AS 100 and another group of routers in AS 200. If you put both ASes on the gateway router then that router will be able to route to all destinations. But routers in AS 100 will not know anything about the routes in AS 200. So how do you arrange the two ASes to talk to each other. There are several options: you could redistribute routes between ASes, or you could configure the gateway router to advertise a default route to routers in both ASes.

But if you do not do something just putting both ASes on the gateway is not likely to solve the problem.



Hall of Fame Super Bronze

Re: IGRP AS Question

Rick, since they are defined as 'gateways' the routes from both ASes would be handled without problems.

Yes, redistribution is another way of tackling this problem but I assume that OP definition of 'gateways'

is the device handling the default route.

For instance, AS100 would default route to its gateway which would have information about AS200. Same goes for AS200 forwarding to AS100.

CreatePlease to create content