route summarization questions

rakem

im just trying to get my head around summarization and how it is actually configured in a network

consider the following network:




so here we have a hub and spoke design with a redundant link between router C. EIGRP is running in the network.

Router B is also a stub network.

now Router B has a ip address of 192.168.1.1 and connects to networks 192.168.1.0 to 192.168.4.0
router C has a IP of 10.1.21.1 and connects to networks 10.1.21.0 > 10.1.24.0
router D has a IP of 10.0.0.1 and connects to network 10.0.0.0 /8

So router B and C have network ranges which can be summarized to help keep resource usage low.
The range router B connects to could be summarized as 192.168.0.0 / 16 and router C's range could be summarized to 10.1.21.0 /16

now my question is on which interface would you actually use the ip summary-address command?
on router B and C would it be the interface that connects back to router A?

its late and im tired so there is probably a bunch of stuff im missing but yea, i just need to know on what interface to use the summary-address command...

thanks[/img]

rakem

can anyone help out with this...

i read somewhere that manual summarization should be configured on the interface which is advertising the route... is this correct?

p.s i think the example above is not really suitable for summarization...

rjbarlow

rakem wrote:

can anyone help out with this...

i read somewhere that manual summarization should be configured on the interface which is advertising the route... is this correct?

This is correct, You have to summarize the routes on the interfaces who advertises the routes and are involved actively in the routing process, in this case interfaces turned to routerA.
For the summarizations they are:
192.168.0.0/21
10.1.16.0/20