Layer 3 Etherchannel Reliability

Unanswered Question
Oct 26th, 2009

Is there a way to do Layer 3 Etherchannel reliably when connecting over a service provider? Any suggestions of protocols is greatly appreciated. Thanks.

I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 5 (1 ratings)
Giuseppe Larosa Mon, 10/26/2009 - 10:29

Hello Mike,

using LACP based etherchannels is a way to have control messages going in each member link.

A link not receiving messages will be put in a suspended state after missing some hellos in a row.

The link will be placed again in bundle when LACP messages are heard again.

At Layer3 you are likely to use eBGP.

with LACP you can also enforce a minimum number of links that have to be up to consider up the bundle.

Hope to help


mikepinto Mon, 10/26/2009 - 10:51


Thanks for the reply. Does LACP actively monitor the link? Let me describe the situation. I have 2 switches connected with a 2 link Etherchannel. Each link is over a different service provider. We connect into service provider switches at each premise. If something happens in service provider network, links are still up in etherchannel, even though down in reality. Even if I down one side of a link, the otherside still shows up in Etherchannel. Traffic that is hashed to go over that link will never get there. We are running EIGRP over the links.

Giuseppe Larosa Mon, 10/26/2009 - 11:00

Hello Mike,

if I've correctly understood your scenario you have bought two Layer2 services to extend two links over two different providers networks.

I think LACP messages should travel over each link with the correct configuration on the Service provider side.

Ask them if they carry L2 signal protocols messages transparently.

if so this can be fine.

if this is not possible I would remove the etherchannel and I would use the two links as two parallel L3 links.

In this case would be EIGRP that can detect one link is down according to its timers (that can be reduced or you can use BFD IP fast convergence).

I would probably choice this second option.

Hope to help


mikepinto Mon, 10/26/2009 - 11:06


Thanks again. Will LACP constantly be sending negotiation packets across the links? I think we are going to go with 2 seperate EIGRP links. Would UDLD also be an option?


Giuseppe Larosa Mon, 10/26/2009 - 11:18

Hello Mike,

yes LACP messages are sent regularly but timers should be 30 seconds by default.

I think that with two L3 links you can achieve faster convergence and you will not rely on Service Provider configuration.

UDLD may not be the right tool here.

Hope to help



This Discussion