BSCI Question: OSPF over Frame Relay

Eric Hansen · ‎02-26-2008

I'm taking a semester long BSCI course one thing that me an another classmate were debating was why would you want to run OSPF over Frame Relay versus just using static routes.

The networks on the other side of Frame Relay cercuits seem to usually be small networks or extensions of networks. Seems like it might not be worth it to run OSPF routing protocol over a Frame Relay link. Just curious why or what some senarios would be to justify this.

thanks

-e

Richard Burts · ‎02-26-2008

E

Sometimes the remote networks are small and sometimes they are not. Even when they are small sometimes you want to know whether they are available or not. Consider the situation of a network with a large central part and some number of remote sites (which might be small). If some device in the central part generates packets with a destination at some remote site, do we want to consume resources in the central network forwarding to the router that has the Frame Relay connection and then that router discards the packet since the remote is not available - and the router would generate an ICMP error indicating Network Not Available which would be forwarded back through the central network. It makes the central network less efficient trying to save some bytes on the Frame Relay network.

HTH

Rick

HTH

Rick

Istvan_Rabai · ‎02-26-2008

Hi Eric,

Just a small addition to Rick's post:

Routing protocols were designed to make the network scalable.

If a remote network becomes unreachable, then the routing protocol will inform other routers about it. If it becomes reachable again, then it informs other routers again.

Now if you have a big network with a lot of remote networks: how would you do the constant modification of the routing tables on all the routers manually, when there is a change in the network topology let's say every half an hour?

And if every 5 minutes?

So you don't have to do it manually by configuring and deconfiguring static routes constantly. The routing protocol will do the modification of the routing tables for you.

Cheers:

Istvan