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VC Uplink on different modules vs H3C LACP, unsupported?

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VC Uplink on different modules vs H3C LACP, unsupported?

Ana had a LACP question:




One of my customers has the following configuration for a VC-H3C environment:


-  On the VC, there is an uplink, Uplink_1, that is formed by the following ports:

  •      Module 1, port X2
  •      Module 2, port X2

-  Both ports are connected to an H3C switch, and that switch has an LACP over the two ports


With that, port X2 on module 1 is active whereas port X2 on module 2 is on standby, as expected.


I wanted to ask if you know any document that tells that kind of configuration is unsupported.




From Chris:

I don’t think using a single upstream switch is unsupported.


Most of our documentation (such as the cookbooks) assume 2 upstream switches – one for each VC module – separate network paths.  Connecting both VC modules to a single upstream switch should be supported but will only be active/standby as you had pointed out.  It’s not optimal but it is supported (in my non-authoritative opinion : )


I’m reserving the right to be corrected.


And from John:

Connecting a port from each VC module to a single switch is supported but not recommended as the switch is a single point of failure. The problem with your configuration is that they have formed a LACP port group using an uplink from both VC modules. You can only form a LACP port group from uplinks coming from the same VC module.


Marc also joined in:

It should be pointed out that any LACP trunks must terminate on the same VC module. In other words, you cannot have 1 LACP that spans over 2 VCs.

See the diagram and note on page 17 here:


Also, the way I see  it, the only time LACP is advantageous in a Active/Standby configuration is if they would be using 2 or more uplinks on a VC module. In this case expect no LACP trunk formed…


Someone please correct me if I’m wrong..




Any other comments or suggestions?