I recently had to configure a LACP port-channel between two FortiSwitches and a stack of two Cisco switches. there is no clear information available on how to do this.

I had to connect two FortiSwitch in MCLAG-ICL configuration to a Cisco 4500 Catalyst switch with a bundle of redundant links. The FortiSwitches were managed by a HA Cluster of two FortiGates in Active/Passive HA mode. The Cisco Catalyst 4500 switch consisted of several 10Gb blades with SFP+ modules.

The fortiSwitches are connected following the diagram shown below.

When you want to connect this all together you have to make sure the FortiSwitches are all connected the right way. My experience is when the FortiSwitches are all showing up in the FortiGate dashboard, this doesn’t mean the MCLAG-ICL is working well. You can check the configuration of the FortiSwitch cluster with the following cli command on the FortiGate:

diag switch mclag peer-consistency-check

After everything is checked and the consistency check shows no errors, you can configure the port channel. First login to the Fortigate and configure the switch controller. Mention the serial numbers of the managed switches where you want to configure the lacp port-channel on.

config switch-controller managed-switch
  edit "FS1E48T419000108"
    config ports
      edit "port46"
        set port-owner "mclag-cisco4500"
        set speed 10000full
        set description "MCLAG-CISCO4500"
      next
      edit "mclag-cisco4500"
        set vlan "vsw.FLink"
        set allowed-vlans-all enable
        set untagged-vlans "qtn.FLink"
        set type trunk
        set dhcp-snooping trusted
        set stp-state disabled
        set description "cisco4500"
        set mode lacp-passive
        set bundle enable
        set mclag enable
        set members "port46"
      next
    end
  next
  edit "FS1E48T419000155"
    config ports
      edit "port46"
        set port-owner "mclag-cisco4500"
        set speed 10000full
        set description "MCLAG-CISCO4500"
      next
      edit "mclag-cisco4500"
        set vlan "vsw.FLink"
        set allowed-vlans-all enable
        set untagged-vlans "qtn.FLink"
        set type trunk
        set dhcp-snooping trusted
        set stp-state disabled
        set description "cisco4500"
        set mode lacp-passive
        set bundle enable
        set mclag enable
        set members "port46"
      next
    end
  next
end

The following command is used to name the port channel. This has to be the same on both switches to form a lacp trunk.

edit "mclag-cisco4500"

In this case I disabled stp with the “set stp-state disabled” command. You have to match the stp version on both the FortiSwitches and Cisco switches. Fortiswitches default use rapid spanning-tree. After the above configuration has been made you have to do some configuration on the Fortiswitches. Logon to the fortiswitches with the following command:

execute ssh admin@169.254.1.2

Replace the ip address with the address of the fortiswitches. Put the following configuration on the ports of the port-channel. You can use lacp-passive on the fortiswitches and lacp-active on the cisco switches.

config switch physical-port
    edit "port46"
        set cdp-status tx-rx
        set description "MCLAG-CISCO4500"
        set lldp-profile "default-auto-isl"
        set speed 1000full
    next
config switch trunk
    edit "mclag-cisco4500"
        set description "cisco4500"
        set mode lacp-passive
        set bundle enable
        set max-bundle 24
        set mclag enable
        set members "port46"
    next

When this has been done you can proceed configuring the Cisco switches.

You can configure the switches by using the following commands:

!
interface Port-channel11
switchport
switchport mode trunk
spanning-tree portfast trunk
spanning-tree bpdufilter enable
spanning-tree bpduguard disable
end 
!
interface TenGigabitEthernet1/1/11
switchport mode trunk
channel-protocol lacp
channel-group 11 mode active
spanning-tree portfast trunk
spanning-tree bpdufilter enable
spanning-tree bpduguard disable
end
!
interface TenGigabitEthernet2/1/11
switchport mode trunk
channel-protocol lacp
channel-group 11 mode active
spanning-tree portfast trunk
spanning-tree bpdufilter enable
spanning-tree bpduguard disable
end

When this has been done you are ready to connect the switches together.

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