Pages

Friday, April 27, 2012

Propagating Default Routes - EIGRP

There are 4 ways to get default routes into EIGRP topology. We will take a look at all of them. Consider a simple 2 router topology and let's begin.

1) Redistributing static into EIGRP.



  • Get interfaces configured 
  • Add a default static route pointing to null0 on R2
  • Redistribute static into EIGRP and notice that R3 now uses R2 as default gateway. 

2) ip default-network

  • R2 loopback 1 with the default gateway 
  • R2 loopback 2 with an extra network just to test
  • R2 ip default-network 2.0.0.0 command
  • R2 eigrp 100 to send 2.2.2.1 advertisement. 
  • Notice that in R3 2.0.0.0/8 appears with a *
  • Notice that R3 can ping 3.3.3.1 (lo on R2) by using a default route. 

3) Summary address 
  • ip summary-address eigrp <ASN> 0.0.0.0 0.0.0.0 <ad|leak-map>
  • Notice that in R3 there is just a default and no other specific routes. 
  • Notice that in R2 a summary route was created pointing to null0
  • Context help and notice leak-map. 
  • Leak-map are similar to route-maps and you can configure a subset of routes that are leaked via summary-addresses. 
4) network everything by typing network 0.0.0.0 0.0.0.0 under the eigrp process. Thanks to Anonymous for the comment.
Many more articles to come so stay tuned. "Join this site" on the right / click +1 below ------->

2 comments:

  1. Once saw a fourth way to do that: use "network 0.0.0.0 0.0.0.0" on EIGRP process.

    All the connected routes get distributed in EIGRP (and not redistributed).

    I don't now if it is an intended feature, or just an idiosyncrasy of that IOS version.

    ReplyDelete
    Replies
    1. Thank you and appreciate the comment. I tested it and it does work. Post has been amended accordingly. Although this process is not very well documented.

      Good catch.

      Arwin R.

      Delete