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Suggestions Needed to Set Up Resilience Across 2 Service Provider L2 Links



I've a Core switch at a DC which links to the HO switch stack via a service provider's LAN Extension Service (LES circuit)

This is fine and probably runs over their MPLS infrastructure.

My problem is that the customer wants another such circuit for resilience and load sharing, but the first one is at layer 2 and configured as a trunk, both the DC and HO are on the same subnet.

The LES circuits do not pass BPDUs, so the switches at either end will become root bridges and cause a loop.

Without changing one side and setting up a routed network, is there a way I can configure these 2 circuits with automatic failover at layer 2?

Any help much appreciated

Regards Tony 


2 Replies 2

Reza Sharifi
Hall of Fame Master Hall of Fame Master
Hall of Fame Master


You can aggregate multiple layer-2 links in a Portchannel. This way if one link fails the other one continue to forward traffic and no need to for STP blocking.  For your Portchannel you can use LACP or PAGP if they are Cisco switches. If they are not Cisco you can use LACP.


Hi Reza,

Thanks for the reply, I did think of that but the service provider would need to configure port channel on their switches too,  and into the same switch stack their end, this wouldn't be possible I'm afraid, so I've have a loop again.

Cheers Tony

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