Need advise on four switch MLAG configuration (ONYX mellanox)

I need some advise to get a four switch (two sites) Mellanox (HPE OEM) SN2010M (ONYX) in a supported configuration.

There are two sites with two switches- each pair in a own MLAG domain (2x100Gbs ISL LACP Channel-Port-Group).

S1 =MLAG1 ISL= S2 site1

S3 =MLAG2 ISL= S4 site2

on Switch 1+3 there are only VLAN3901 access ports
on Switch 2+4 there are only VLAN3902 access ports (is a iSCSI configuration with two separte VLAN/subnets)

There are 4 connections possible between the two sites, and should be fully redundant or only redundant on each VLAN/Subnet.
How to configure that without any loops, no success with MLAG-Port-Channel or normal port-channels with 4 connections from site to site, straight and crossover, or straight only .

Thanking for any help,


Hi Martin,

I would start with the documentation to understand the capabilities and limitations:
Not all of this documentation is relevant for what you need but you can have a look.

I am not entirely clear on the design constraints and a forum like this is a bit challenging to get design guidance.

Can you create a diagram of the design that closest meets the needs with the switches + interfaces listed +VLAN/TRUNK, along with site description of something that did not work?

Let’s see if we can hash out where it is wrong and what would be a supported configuration.


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Hallo Charles

Thank you for your response. I am aware of the documentation how to get MLAG working and how to create channel groups with and without mlag. But in this case I got no clear view if it is supported or not. Please see the picture.

The hand drawn lines are the four connections between the sites and switches.

One opinion is that this configuration is not supported only a spine leaf configuration with more switches.
2nd opinion was the only supported config is to get the MLAG not between the switches on one site but on each switch to the other site.

In the MLAG documentation there is such a configuration as drawn mentioned but no more details to avoid loops over the MLAG isl.

Thank you for any input.

Hi Martin,

Thanks for the additional clarification on this.

IMO, MLAG is not the correct solution here due the localized VLANs and redundancy requirements. For MLAG to function correctly we need all VLAN’s on both peers. Your MPO would not meet those requirement based on where the VLAN’s reside.

Have you considered VXLAN? This would allow the inter site & inter switch links, which would be L3, to be all active and each switch could have any (or no) vlans.


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MLAG with too much distance can cause issues. I agree, I would look at using VXLAN/EVPN.