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Friday, March 5, 2010

How can you redistribute any route into OSP?

We have 2 routers at home network. 2650xm ix connected to ISP Cable modem 2620 is connected to 2650XM by switch and they both are in same network.
Routing protocol config on 2650

router ospf 10
redistribute connected
network area 0
router rip
version 2
default-information originate

Why does router 2620 learn route from 2650, using rip as default? As ospf has less AD which is 110 then rip? Right now 2650 is advertising routes to 2620 router by Rip and OSPF and 2620 has chosen Rip protocol as compare to OSPF. Can someone explain why this is so?

You can redistribute any route into OSPF with the exception of the default route.
To generate a default route into OSPF
  1. You need the default route in the router generating the advertising along with the command default information-originate
  2. You can use the command default information-originate always when the router does not have a default route on its routing table.
If you want the 2620 router to obtain the default via OSPF, we would recommend using option 1.

The 2620 has chosen the RIP default-route because only RIP is sending a default-route from the 2651. Using "redistribute connected" under the OSPF configuration will not tell OSPF to advertise a default route.
So if you want a default-route to be advertised by OSPF as well as RIP you need to use one of the options listed above.

If two routers are ospf neighbors then they will exchange the hello packets with respect to time-interval's configured on those interfaces.

If the 2620 needs to reach the internet, per your current configuration, it will use RIP to reach the router advertising the default route.
Once the packet reaches the ASBR router, it will use static to reach the internet (next hop
The packet won't be dropped unless you have NAT issues.

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