EIGRP Question/Suggestion

Unanswered Question
Apr 30th, 2010

I'd like some detailed opinion on this...

Is it a good practice to establish eigrp neighborships between core routers using the SVIs as the routed interfaces?

In other words, I have 2 core switches running eigrp, with SVIs for about 20 vlans configured on each, as well as HSRP.

And then there is a L2 trunk between the switches that allows all the vlans.

Instead of running a separate connection and assigning a /30 and running eigrp on it, the SVIs are being used for the neighborships - so what they have are about 10 neighborships between the same two core switches.

That seems kind of hoky...I dont like using SVIs for this purpose because a bridging loop would then effect the L2 data plane as well as the L3 control and data planes....

Moreover, you would have routing updates being generated by each SVI neighbor interface that has eigrp running on it, thereby creating a whole hell of a lot of redundant traffic...

What do you guys think?

[EDIT] By the way, they are running CatOS {EDIT}

Victor

I have this problem too.
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Edison Ortiz Fri, 04/30/2010 - 09:50

Select one SVI to be the 'routing protocol' SVI and apply passive-interferace default under the EIGRP process with no-passive just for this SVI.

That's the BP suggestion I give to customers for EIGRP and OSPF.

I do agree with you, having multiple neighbors between switches does create routing instability. For instance, if one of the SVIs go down due to the last switchport associated to that SVI leaving the switch, it will drop the EIGRP neighbor which can potentially affect a flow as the traffic between EIGRP neighbors will be load balanced to the number of neighbors with the exact same route.

Regards

Edison.

lamav Fri, 04/30/2010 - 10:09

Thanks, edison.

I was actually thinking of creating a totally new vlan with a /30 mask just for the purpose of peering. This way the bridging loop possibility is all but completely mitigated for that connection because itll be nothing but a p2p.

To be specific, I would create a L3 etherchannel and use that /30 on it.

Victor

Jon Marshall Fri, 04/30/2010 - 11:12

lamav wrote:

Thanks, edison.

I was actually thinking of creating a totally new vlan with a /30 mask just for the purpose of peering. This way the bridging loop possibility is all but completely mitigated for that connection because itll be nothing but a p2p.

To be specific, I would create a L3 etherchannel and use that /30 on it.

Victor

Victor

If it's CatOS not sure you can have a L3 etherchannel ie. it will have to be a L2 etherchannel with as you say a /30 using SVIs.

Jon

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