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MLAG configuration is very similar to port-channel configuration. It is recommended to keep the same port in each switch within the same mlag-port-channel (not a must). In this example, there are two MLAG ports, one for each host (host s1 is connected to mlag-port-channel 1 and host s2 is connected to mlag-port-channel 2).

The "mlag-port-channel" number is globally significant and must be the same on both switches.

  1. Configure the following on both switches:

    sx01 (config) # interface mlag-port-channel 1-2
    sx01 (config interface port-channel 1-2 ) # exit
  2. Set the mode (LACP or static) - Only one option is applicable:
    To set the MLAG interface in static mode run:

    sx01 (config) # interface ethernet 1/1 mlag-channel-group 1 mode on
    sx01 (config) # interface ethernet 1/2 mlag-channel-group 2 mode on

    To set the MLAG interface in LACP mode, run:

    sx01 (config) #
    interface ethernet 1/1 mlag-channel-group 1 mode active
    sx01 (config) # interface ethernet 1/2 mlag-channel-group 2 mode active

    LACP mode 4 should be configured on the host side. Configuring LACP is similar in LAG and MLAG ports. LACP notifications arrive via the control protocol and not via the port physical status. It will show the remote system-id and may encounter configuration errors. LACP is very valuable, especially in large scale configurations with multiple MLAGs, as it helps detect any mismatched configurations in terms of connectivity.

  3. Enable the two interfaces:

    sx01 (config) #interface mlag-port-channel 1-2 no shutdown
  4. To change any MLAG port parameter (e.g. MTU), enter the MLAG interface configuration mode and perform the change:

    sx01 (config) # interface mlag-port-channel 1-2
    sx01 (config interface mlag-port-channel 1-2 ) # mtu 9216 force

    Some operations may require "force" or manual disabling of the link.

  5. To change the LAG/MLAG port speed, all interfaces should be removed from LAG/MLAG while changing the speed in the member interface configuration mode.
    It is recommended to configure the ports speed before adding the ports as members to the LAG/MLAG port, as once the ports are members in a LAG/MLAG the speed cannot be modified without removing the port from the LAG/MLAG.

  6. To verify MLAG configuration and status, run the following commands:

    sx01 [my-mlag-vip-domain: master] (config) # show mlag
    Admin status: Enabled
    Operational status: Up
    Reload-delay: 30 sec
    Keepalive-interval: 1 sec
    System-id: F4:52:14:11:E5:38
    MLAG Ports Configuration Summary:
    Configured: 2
    Disabled: 0
    Enabled: 2
    MLAG Ports Status Summary:
    Inactive: 0
    Active-partial: 0
    Active-full: 2
    MLAG IPLs Summary:
    ID Group Vlan Operational Local Peer
    Port-Channel Interface State IP address IP address
    1 Po1 4000 Up
  7. To verify MLAG domain status, run:

    sx01 [my-mlag-vip-domain: master] (config) # show mlag-vip
    MLAG group name: my-mlag-vip-domain
    MLAG VIP address:
    Active nodes: 2
    Hostname VIP-State IP Address
    sx01 master
    sx02 standby
  8. To see MLAG interfaces summary, run:

    sx01 [my-mlag-vip-domain: master] (config) # show interfaces mlag-port-channel summary
    MLAG Port-Channel Flags: D-Down, U-Up
    P-Partial UP, S - suspended by MLAG
    Port Flags: D - Down, P - Up in port-channel (members)
    S - Suspend in port-channel (members), I - Individual
    Port-Channel Type Local Ports Peer Ports
    (D/U/P/S) (D/P/S/I) (D/P/S/I)
    1 Mpo1(U) Static Eth1/1(P) Eth1/1(P)
    2 Mpo2(U) Static Eth1/2(P) Eth1/2(P)