One ABR router with two instances of OSPF & 1 VL = 1 problem

Carles P R · ‎04-20-2010

Hello,

I'm having a problem which I don't know how to fix... if you can help it will be useful for my training to CCNP and further CCIE.

Here is the topology:

Baseline: R3640veu is running two OSPF processes (100 and 200). As you can see pid 100 is ABR in area 15 and pid 200 is ABR in area 26. There are two virtual links that connect area 25 and 26 to backbone area. Each process has configured the other's process interfaces as passive. All areas are regular areas without any filters anywhere.

My problem: routes from area 15 that are sent to backbone area and then to area 26, when R3640veu, the ABR receive the routes from area 15 they are not sent to the other area 26 routers but when I turn off the Frame Relay switch of area 15, R3640veu doesn't has a better path to arrive to area 15 routes than going through all the areas.

I can understand that when the router receives the DBD it processes all the information and compare the routes it has with the received ones and update its routing table with the best paths to on destination network so I understand that its routing table has as a best path to area 15's routes the way through the Fame Relay cloud. However, if I type the command "show ip route 10.0.0.34" (IP of area 15) in R2610xmveu (not an ABR, it is in area 26 as well as R3640veu) it doesn't has any route to the destination network but when I turn off the FR switch, it has a route to reach area 15 networks, ping it and everything is fine then.

I understood that when a router receives LSDB information, it floods ALL the information through the area without filtering anything but with the problem I am having it seems that R3640veu is filtering the routes to which it can arrive so other routers don't get the information until the ABR losses its route to these destinations.

I'll thank a lot your help!!!

Best regards,

Carles

Giuseppe Larosa · ‎04-21-2010

Hello Carles,

all non-zero areas should have a direct connection to area0 of their OSPF domain

An OSPF area 0 should exist for each domain if both domains are multi Area

on a single node each link can be part only one process and area-id combination

A non-zero area not connected to area 0 requires a virtual-link going via a standard area connected to area 0.

Try to use a network design that is more similar to real world scenarios, no one is going to create a daisy chain of OSPF areas as you did in this lab.

going through other non-zero areas is not a sane option.

An ABR connected to area 0 changes its behaviour and this is what you have seen in this lab.

Hope to help

Giuseppe

Carles P R · ‎04-21-2010

Oook! Thank you very much, I'll remake the topology hehe!

Best regards,

Carles