Posted on August 3, 2020 9:54 pm
 |  Asked by Matthew Taylor
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Hello, I am new to Arista and am reading through Arista Warrior and trying to build a simulated Arista lab.  Using Box or Vmware workstation I run through the establishing MLAG peer link but it never comes up.  I can ping the management ip of each switch fine but I cannot ping the peer link ip from either side.  I am using PO1000 on each side and they are up.  Is there something I am missing.

Answered on August 3, 2020 10:01 pm

Hi Matthew.

Have you configured the trunk group and/or made sure the spanning-tree was not blocking the traffic in the VLAN used for MLAG (local interface/peer-address)?

The show interface trunk output could be useful to check that.


Posted by Matthew Taylor
Answered on August 4, 2020 1:38 pm

Hello Diogo yes I created the trunk group MLAG-Peer and ran the no spanning-tree vlan-id 4094 command on each switch.  Running sh trunk so I only see vlan 1 which explains why its not coming up.  I need to allow traffic on 4094 on the trunk correct?

Posted by Lokesh Charora
Answered on August 4, 2020 2:10 pm

yes Matthew, The VLAN4094 has to be enabled on the trunk. As per Arista warrior example:

With the port-channel configured as a trunk, we need to create a VLAN that will be used only for MLAG peer-to-peer communication. The Arista examples use VLAN 4094, so let’s keep that tradition alive:
Arista-1(config)#vlan 4094
Arista-1(config-vlan-4094)#trunk group MLAG-Peer <<< Assigning VLAN 4094 a trunk group.

The trunk group MLAG-Peer command creates a trunk group, which is a cool way of assigning VLANs to trunks. We now need to assign the same group to the peer-link:
Arista-1(config-vlan-4094)#int po 1
Arista-1(config-if-Po1)#switchport trunk group MLAG-Peer <<< enabling the trunk group on peer link

Now, VLAN 4094 will only be included on trunks that are also assigned to the MLAG- Peer trunk group. By doing this, when we create a new trunk, by default VLAN 4094 will not be included. This keeps the MLAG peer-link traffic on this link, and only on this link (unless you add the MLAG-Peer trunk group to another trunk, but don’t do that).

Posted by Matthew Taylor
Answered on August 6, 2020 9:51 pm

Thank you Lokesh I have it running now.  Have another Q coming for VARP in a L2LS.

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