Etherchannel over a Providers Network (WAN)

[mcroft]

Hi,

I have two switches, one in Datacentre-A and the other in Datacentre-B.

The switches are connected via a layer2 interconnect (provided by the Service Provider). I suspect they are running a MPLS/VPLS cloud back end.

Now, we need a second (L2) link for resiliency through a separate second provider.

Question, can I run Etherchannel across this “WAN” ? I am suspecting I could run into a few problem (detecting wan link failure within the provider's cloud, whilst the local interface remains UP)

Any help really appreciated.

Alternatively, I just run STP, and block the secondary interconnect, but not as good.

Thanks for reading

Matt

[Giuseppe Larosa]

Hello Matt,

the recommendation is to try to use LACP so that LACP control frames are exchanged on each member link.

IF one link fails LACP will remove the link from the bundle and switches will use the surviving link. When fault is restored the link is added again to the bundle.

To be noted STP does not run on all member links of a bundle as it sees it as a single logical link.

channel-group N mode active

to use LACP

WARNING: there are cases where the LACP frames are not flowing on one link depending on how the service is provided, so you need to test the solution on each link.

Hope to help

Giuseppe

[mcroft]

Thanks for the reponse Giuseppe.

One of my worries, is that the provider network fails. (and both local interfaces stay up)

how long would it be before LACP detects failure and bring down the link ?

I guess the LACP link detection would be needed and that could take a while.

thanks again.

Matt

[Giuseppe Larosa]

Hello Matt,

>> I guess the LACP link detection would be needed and that could take a while

You are right on this it will take the time of expiring a timeout.

I don't see in configuration guide a way to reduce the LACP timers on Cisco switches.

Hope to help

Giuseppe