EIGRP & VLSM

[jsalminen]

Is it good practice to include the subnet mask with the network advertisement entries for EIGRP. I have entered the networks in this format:

network 10.0.0.0

network 172.16.0.0

network 192.168.0.0

When I view the routing tables on the other routers it shows a summary-like entry and the complete network address (10.100.128.0).

Is it good practice to include the subnet mask in most cases with EIGRP?

[donewald]

Subnet mask in the network statement just allows you to identify which interfaces will participate within EIGRP.So, yes, it is good practice to include this to give you better control of which interfaces are in your EIGRP process. If no-auto summary is enabled with in your EIGRP process you'll see subnets within your classful network statements rather than only seeing the classful (e.g. 10.0.0.0/8) network.

Hope this is what you were looking for,

Don

[jsalminen]

That makes sense it terms of not summarizing the subnets into classful statements. I'm not clear about how the subnet mask identifies the interface though. Fortunately, I have the latest BCSN training book so I will just have to review this.

[wolfrikk]

One other thing to note is that EIGRP automatically summarizes routes at network boundaries when it can. You can disable this by adding "no auto-summary" to your EIGRP process.