EIGRP on Secondary interfaces

[h00nix101]

Is it true that EIGRP will not form neighbours with

ip's that are on secondary interfaces?

I have a need to add a /29 to an exisiting /30 network, and I'd rather it not take part in the

EIGRP relationship.

Thanks

[Richard Burts]

I am not clear what you are attempting to accomplish. You say that you are adding another network as a secondary on an interface but that you would prefer that it not take part in the EIGRP relationship. Does that mean that you do want EIGRP to advertise the network or you do not wawnt EIGRP to advertise the network?

It is true that EIGRP will not use a secondary address and try to form neighbor relationships with the secondary address. EIGRP uses the primary interface address as the source address in the HELLO packet used to form neighbor relationships.

HTH

Rick

[h00nix101]

I'm installing WAN optimization hardware, I don't want EIGRP to form any neighbour relationships over the secondary network.

And I don't want the network to be advertised in the routing tables.

So I believe I can achieve this by the use of a secondary network.

Thanks

[Richard Burts]

EIGRP will not attempt to establish a neighbor relationship using the secondary address. So you should be covered on that aspect.

If the secondary address does match one of the EIGRP network statements then the secondary address will be advertised by EIGRP. If you do not want the subnet to be advertised then you either need to use EIGRP network statements with explicit masks that will not match the secondary network or you need to implement distribute lists on the EIGRP advertisements to supress the secondary network.

HTH

Rick

[vcjones]

Good advice so far, a few more things to watch out for:

The newer IOS releases allow specifying a netmask in your EIGRP network statements. Otherwise, legacy "class" rules are assumed. Also watch out if you have auto summarization enabled in EIGRP (there should be a line "no auto summary" under "router eigrp..")

All routers on the LAN with the secondary IP which are EIGRP neighbors on the primary IP must have the secondary IP subnet defined on the interface. You won't get any error messages if you don't, but routing may not work right unless you do.

Good luck and have fun!

Vincent C Jones

www.networkingunlimited.com