Redistributing static routes into OSPF in stubby area

[astrand]

Hi,

We have a number of smaller sites connected to our main site with serial lines. In order to decrease the size of the routing tables in the remote sites, we would like to configure them as stub areas. However, in some of the locations we are using routers that are not running OSPF and therefore we have defined static routes to networks behind those devices.

Is it possible to redistribute these static routes into OSPF from a stub area?

(Some of the routers are running IOS 11.0 and thus do not support nssa)

You help would be very appreciated!

Regards,

Harald

[wolfrikk]

The "redistribute static" command will redistribute static routes into the OSPF process. You can use "redistribute connected subnets" to redistribute networks that are on the router, but do not have a network statement in OSPF. You may have to change the default metric using.

redistribute static metric

Hope that helps.

[deilert]

This is not possible when you redistribute in to OSPF the routes become external type 5 lsa's Type 5's are not accespted in to stub areas

[wolfrikk]

Those routes will not show up in the stub area, but the ABR should have the routes in its routing table. That way, the stub area routers will send all external traffic to the ABR by default, then the ABR will know where to route the traffic. The static routes do not have to be added to the stub area router's route tables for them to be able to route traffic to those networks.

[wolfrikk]

I just realized I misread part of the original post. The previous post was right about not being able to redistribute external routes directly into a stub area. You will either have to upgrade the IOS to support NSSA or convert that area to a regular area. You can still control route table size with router aggregation is there are a lot of networks.

[kenjordan]

Let me see if I understand your question correctly: Your main site runs OSPF. You have two types of remote sites: a) sites that are running OSPF and configured as stubs and b)sites that are not running OSPF.

If this is correct, then it's my understanding that you will need to configure static routes on the main site ABRs(the ones that are attached to the non-OSPF routers) and redistribute them into OSPF using the "redistribute static subnets" command(on the ABR). This will allow the routes to these remote sites to be propagated through the backbone area so all routers will know how to reach the remote destinations. On the non-OSPF remote site routers, you will need to configure a default route, ie. "ip route 0.0.0.0 0.0.0.0 x.x.x.x" where x.x.x.x is the ip address of the ABR router's connected interface, to allow them to reach all other destinations.That takes care of the non-OSPF routers.

For the routers running OSPF, by configuring them as stubs, they automatically have a default route to the ABR entered into their routing table. Since their ABR knows routes to all other destinations, they have full network connectivity. You could even configure them as totally stubby areas to further reduce the routing tables.

Notice that these configurations will reduce the size of the routing tables in the remote sites but will increase the size of the tables in the main site because of the static routes.

Hope this helps,

Ken