Posted on May 29, 2015 11:28 am
 |  Asked by Victor
 |  1814 views
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Hi,

I wanted to know if MLAG has the same issue as Cisco’s VPC. Specially regarding “Orphan Ports”? If so how do the Arista switches deal with this?

 

Thank you,

Victor

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Posted by Alexis Dacquay
Answered on May 29, 2015 11:55 am

 

Hi Victor,

Could you detail what your mean by orphan ports ? Obviously they are single-attached devices, but it can mean per design, or do you also include into that servers that are dual-attached in active-backup mode, and also port-channel/port-binding with a link failure (only 1 link remains) ?

 

Taking the general meaning of ”orphan”, a device can be sending traffic to only one of the MLAG peer (e.g. peer 1), the traffic that need to reach a remote destination would then either be:

1) forwarded locally to the peer 1 if that destination is locally known

2) forwarded to the peer 2 across the MLAG peer link if peer 2 knows about it.

 

The best practice is to have active-active dual-home connection for all the attached nodes. This avoid traffic crossing the MLAG peer-link. Local switching is line-rate, avoiding the peer-link bottleneck.

If you have a lot of orphans spreading on both sides (attached on Peer1 or on Peer2), then make sure your provision your peer link bandwidth accordingly, traffic will cross it. Ordinary, Layer2 and Layer3 traffic would be locally-switched and would not cross the peer-link

Additionally, make sure the peer-link is resilient (has multiple physical links bundled).

 

Here are some articles related to MLAG:

https://eos.arista.com/mlag-basic-configuration/

https://eos.arista.com/mlag-advanced-configuration/

https://eos.arista.com/active-active-router-redundancy-using-varp/

 

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