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  • 1.  MLAG between two VSX

    Posted 10 days ago

    Hi,

    i am new on Aruba and i am trying some stuff in labor.

    i have  five switches, the  SW5  is connected with SW1 and SW3.   On SW5 ist LAG.

    SW1 is with SW2 in VSX and SW3 with SW4 in VSX.    

    in SW1 and SW3 i have MLAG where is  the SW5 connected ,  SW1 and SW3 are also with LAG connected.

    i thought MLAG will worked out but the one port is going blocked.

    Is that normal? or i forgot something?

    Thanks a lot



  • 2.  RE: MLAG between two VSX

    Posted 10 days ago

    Hi

     

    Thanks for reaching out to the community.

     

    I think your topology you set up technically cannot work. When building a port-channel (aka LAG), you need to make sure that you only two (not three or four) (logical) systems through that port-channel. Otherwise that won't work.
    LACP checks the partner-ids of all member link in the channel and makes sure all member links are connecting to the same partner. This also applies to port-channels which physically end-up on different hardware (such as a VSX cluster).
    The trick that is made here is that the two physical system share a common system-id and exchange certain information such as MAC address tables, Spanning-Tree states, LACP states etc. with each other. Such, they can appear to another system which is connected to that Multichassis LAG (MLAG or MCLAG) as a single system. So, a server or switch or firewall or whatever you connect doesn't "see" that the links are physically connected to different hardware as they appear as one logical system.

     

    Such a logical system you can build-up by using VSX clustering. If VSX is configured correctly, you can establish a multichassis LAG from a system to SW1/SW2 pair OR to SW3/SW4 pair. Mixing among the pairs is not possible (e.g. SW1 and SW3) as they are not exchanging the required tables and states and don't share the common system-id.

     

    So, to make your setup work, SW5 should connect it's LAG interfaces to SW1 and SW2 or SW3 and SW4 but not SW1 and SW3. Depending on your L2 setup and needs, you may setup two LAGs, one to SW1/SW2 pair and one to SW3/SW4 pair.

     

    I hope this helps.

     

    For reference, see also:

     

     

    Regards,

    Thomas

     




    Original Message


  • 3.  RE: MLAG between two VSX

    Posted 10 days ago

    ok thanks for the reply


    Original Message


  • 4.  RE: MLAG between two VSX

    Posted 10 days ago

    Do you have a diagram?

    We only do MC-LAG to members of the same VSX pair. 

    So lets say, SW1 and SW2 are a VSX pair. You can connect SW5 to this two switches using MC-LAG. Please also check the VSX guide. 

    A simple configuration example within the VSX.

    interface lag 1 multi-chassis
  no shutdown
  no routing
  vlan trunk native 2
  vlan trunk allowed 1-3,5-6,13-15
  lacp mode active
  lacp fallback
  spanning-tree root-guard

interface 1/1/1
  description DOWNLINK_TO_ACCESS_SW_OR_CTRL
  no shutdown
  lag 1 
  mtu 9198


    ------------------------------
    Willem Bargeman
    Systems Engineer Aruba
    ACEX #125
    ------------------------------

    Original Message


  • 5.  RE: MLAG between two VSX

    Posted 10 days ago
    ok thanks for the reply, yes i have one.   But like i read before my scenario is not possible because are two different vsx. 

    Original Message


  • 6.  RE: MLAG between two VSX

    Posted 10 days ago
    Edited by willembargeman 10 days ago

    That will not work. It is possible now. However, you need to use EVPN-VXLAN. This is called EVPN-VXLAN multihoming 



    ------------------------------
    Willem Bargeman
    Systems Engineer Aruba
    ACEX #125
    ------------------------------

    Original Message


  • 7.  RE: MLAG between two VSX

    Posted 10 days ago

    In your scenario you can't use LAGs at all. You can use physical ports (without LAG) to connect to each VSX cluster and leave spanning tree to resolve loops (or just use different vlans on each link) or use L3 ports and route appropriately.

    Best, Gorazd



    ------------------------------
    Gorazd Kikelj
    MVP Guru 2025
    ------------------------------

    Original Message


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