Redundamcy between OSPF areas

daniel-nilsson · ‎10-22-2008

Hi

If one site at AREA 10 drops the connection to AREA 10, then we can access this site via AREA 20 with the help of static routs with distance higher than OSPF default 110 and static routs redistribution in OSPF.

How do we do this, if we configure summary or stub to reduce size of the routing table?

Many thanks

/Daniel Nilsson

Joseph W. Doherty · ‎10-22-2008

Another solution might be to make your area 10 rtr that has contact with area 20 an ABR either via a virtual link or perhaps even a GRE tunnel.

daniel-nilsson · ‎10-28-2008

An gre tunnel through area 20 could fix this problem. A static route to a loopbak on the ABR for area 10 via area 20, the link between areas announces by area 20. Tunnel source/dest between area 10 link ip address and the loopback on area 10 ABR. The tunnel will be a area 10 network. With this, the summary of area 10 will be intact, and full dynamic in the routing. I only need to adjust the ip ospf cost on the tunnel so that traffic wouldnt use the gre tunnel primary. I have tryed this and it works just fine.

Thank you for the gre advice

/Daniel

Joseph W. Doherty · ‎10-28-2008

The downside of using a GRE tunnel is possible impact of the reduced MTU, but if only used as failure option, shouldn't be a major problem.