EIGRP Network Configuration

[techkiwi]

Probably a basic question with many answers!

If you have 2 routers connected to each other over a WAN link you can configure the serial interfaces on each with a /30 mask, right? Say:

192.168.1.5/30 and
192.168.1.6/30

Now, if you're configuring up EIGRP, would you configure the MAJOR subnet number or the CLASSLESS one (I think I'm using the correct terminology).

In other words, would you use:

rtr(config-router)#network 192.168.1.4 255.255.255.252 or
rtr(config-router)#network 192.168.1.0

Thanks

Graham

 

[jimmyzz]

No problem summarising the network at 192.168.1.0 unless you specifically wanted to excluded one of the /30 networks from the eigrp topology.

JimmyZ

 

[techkiwi]

So is it standard practice to just stick with the network 192.168.1.0 statement? (Sorry if it's a dumb question, I don't get to play around with routers much in the real world, just in a lab).

 

[IPKONFIG]

Yes Techkiwi, standard practice is to use the network statement 192.168.1.0 General rule is: Keep the config small.

"I can picture a world without war. A world without hate. A world without fear. And I can picture us attacking that world, because they'd never expect it."
- Jack Handey, Deep Thoughts

 

[tbilan]

Normally people keep their network statements classful (10.0.0.0, 192.168.1.0 etc.) This works fine unless there is an interface with a subnetted address that you do not want to talk EIGRP on but then you can fix that a few ways. If you don't want to announce or listen at all on an interface use passive-interface INTERFACEID. If you want to limit what you receive or send then use a distribute list in/out and make a matching access list. We use this because we route for multiple customers who should be able to get to us but not to each other so for example:

router eigrp 12
network 192.168.1.0
distribute-list 30 out Serial1/0.372
distribute-list 30 out Serial2/0

access-list 30 permit ip 1.1.1.0 0.0.0.255
access-list 30 perimt ip 2.2.2.0 0.0.0.255

The above will only send the 1.1.1.0/24 and 2.2.2.0/24 to neighbor routers on those Serial interfaces so they don't get our full routing table.

Hope this is of some help.


Tom Bilan
TJBA, Inc.
CCNP, CCDP, MCSE & CNE

 

[techkiwi]

Thanks for all the insight, folks! Much appreciated.