Posted on March 23, 2016 5:23 pm
 |  Asked by Lukas Hubschmid
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I am currently testing the L2/MLAG-Design in GNS3 using vEOS.
My topology consists of 2 spine switches and 3 pairs of leaf switches (=6 leaf switches).The 2 spine-switches will form an MLAG peering, as well as each of the leaf switch pairs.
Each leaf is connected to both spines –> bowtie MLAG.

Now my questions:
1. If I have multiple leaf pairs, can I use the same MLAG domain-ID for each leaf pair, or should I use a distinct one for each pair?
2. Is there any reason I should not use the same 2 IPs for MLAG peering on all leaf pairs (e.g. leaf A is always, leaf B is always

What are the best practises regarding this?

Many thanks in advance!

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Posted by Alexis Dacquay
Answered on March 23, 2016 5:41 pm


The MLAG configuration is only local to the pair involved in the domain.

You could therefore have the same domain-ID everywhere.

You could also use the same /30 or /31 subnet for peering everywhere, just be careful not to advertise that subnet in your routing protocols. But it should be fine in a pure L2 environment as you mention. However with L3 Leaf-Spine, you would have to think about running routing protocols northbound of  the Leaf pairs, and for resilience you would need routing between the peers, so that /30 or /31 might need to be advertised. It al depends on your L3 design. For a strictly L2-only then it would not matter.

For reference:




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