EIGRP Static Neighbor

Lessons Discussion
9

Hi Syed,
I have an answer for you. Your detailed information was very helpful, so thanks for that. EIGRP does NOT advertise static routes (except if you tell it to do redistribution), unless it considers the route to be connected to a local interface. To understand this, you should know that static routes can be defined two different ways:

  1. The route can point to a next hop address, as you have done: ip route 192.168.4.0 255.255.255.0 192.168.24.4
  2. The route can point to an interface such as: ip route 192.168.4.0 255.255.255.0 serial0/0/0

When you use an interface as the destination, the router assumes this is a point-to-point connect so there is only one possible destination (the router on the other side). In an multi-access environment, such as Ethernet, this will not work because there could be multiple devices on the other end of the connection.

Now, let’s tie this back to EIGRP. As odd as it may seem, EIGRP considers any static route with an interface as a destination to be “directly connected” and thus eligible for advertisement within EIGRP via a “Network” statement. You can test this by doing the following:

no ip route 192.168.4.0 255.255.255.0 192.168.24.4
ip route 192.168.4.0 255.255.255.0 null0

By changing the static route from using a next hop destination to an interface destination (null 0 counts as an interface), you should see this route being shared within EIGRP.

Now that you know this, you can solve your original problem where you had Internet->ASA-> R1-> R2 -> R3-> R4. You have to cheat a bit to do it, though. If you are determined not to use static route redistribution with a distribute-list for filtering, you can create a “fake” summary route on R1 that includes 192.168.2.0 - 192.168.5.0, route that to null0, and it will be advertised via EIGRP. Try this via R1:

R1(config)#ip route 192.168.0.0 255.255.252.0 null0
R1(config)#ip route 192.168.4.0 255.255.254.0 null0
R1(config)#router eigrp 1
R1(config-router)#network 192.168.0.0 0.0.7.255

When you do this, R4 will be able to route to 192.168.3.0/24 and 192.168.5.0/24 without a default route like you wanted, but there will be extra subnets in there as well. If you wanted precisely just the 3 and 5 network, you would have to use redistribution with a distribute-list filter.

--Andrew

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