OSPF to BGP Route metrics

[Joseph Dworak]

We copy large amounts of data from a host in site C to a host at subnet 10.234.0.0/22.  I have two paths to get from C to the host.  One is perfered by us due to larger bandwidth.  The link between C -B is a gig and B-A is a Gig.  The link between C-Z is 100 meg. 

Both of the A and Z routers are on the same OSPF area on the LAN side and different BGP AS on the WAN side.  I want to advertise the route from Z to be a higher metric so it is not the perfered route.  I want traffic from teh 10.232.x.x network to chose the C-B, B-A.  The C-Z is an alternate backup for this data copy.

How can I advertise from the A and Z router the 10.234.0.0/22 so it is a higher metric from Z than A?

[milan.kulik]

Hi,

don't forget you need to influence both traffic directions.

If you need just a temporary solution, the easiest way would be:

Configure two static routes on your router A:

One for the host in 10.232.0.0/16 subnet, using 10.32.255.1 as next-hop. Redistribute this route to OSPF (but not to BGP!).

Second for the host in 10.234.0.x/22, using 10.234.0.7 as next-hop. Redistribute this route to BGP (buit not to OSPF!).

As "longest match wins", router A will be always preferred for the communicatiopn between those two hosts.

Remopve those host static routes when finished with your file transfer.

If you need a long-term solution, you should reconfigure the OSPF/BGP mutual redistribution to advertise 10.234.0.x/22 subnet with worse attributes (by AS prepending, e.g.) from router Z to BGP.

And also to advertise the 10.232.0.0/16 with worse OSPF metric from router Z to the OSPF cloud.

But this is a little tricky and you need to know the curent metrics used for the routes.

HTH,

Milan

[paulstone80]

Hi,

Rather than influencing the Routing Protocols, you could use Policy Based Routing to achieve this.

Kind regards,

Paul