MLAG towards VPLS

Userlevel 2
I have a question that is causing me headache. I have two PE routers of another brand that Extreme.
I want thoose two PE routers to run VPLS towards two MLAG extreme that is connected like this.

I have not been able to test this but I would form a loop in the VPLS network or will the ISC block traffic between ?

4 replies

Userlevel 4

Are both PE routers Extreme switches? If not, I think your MLAG topology is wrong.
Even if the PE routers are Extreme switches, I don't think MLAG can be redundant protocol for VPLS.
Userlevel 7
Hello Andreas,

do you intend to connect the X670 switches via layer 2 to the PE devices? If yes, then the X670 MLAG pair will not forward a frame it received via an MLAG port back through the same MLAG port. The MLAG port is a logical construct comprising physical ports of both MLAG pair switches. The ISC will not create a layer 2 loop for (correctly configured) MLAG ports.

You should use LACP for the multi chassis LAG to avoid cabling errors and ensure that both sides are configured for (multi chassis) LAG. You need to ensure that the PE devices can be used in an active/active mode, because all active MLAG ports will be used by the Extreme switches to send frames. An active/standby model of the PE boxes could in theory be implemented by deactivating the secondary PE's link via LACP. The possible solutions depend on the PE features.

If you want the Extreme switches to participate in VPLS/MPLS, you should not use an MLAG, but layer 3 connections.

Userlevel 2
Thanks for the explanation around this. Per design VPLS services not in active-passive ( BGP signaled) will be active-active however will there be the same source-adress at both PEs?
I have trouble wrapping this around my head. Will the PE learn the same source-mac on both interfaces ?

Then we might trigger the mac-move detection in the PES-
Userlevel 7
Hi Andreas,

since LAGs are usually configured to load-share flows, a given MAC address can be seen on all physical ports of the LAG. But since this is a logical port, the MAC is learned on this one port only.

Of course, both sides of the LAG must be configured as a LAG for this to work.