Cumulus defines cLAG or mLAG as "Multi-Chassis Link Aggregation (MLAG) enables a server or switch with a two-port bond, such as a link aggregation group/LAG, EtherChannel, port group or trunk, to connect those ports to different switches and operate as if they are connected to a single, logical switch. This provides greater redundancy and greater system throughput.

This Article explains mLAG function in great detail.

In simple terms, cLAG enables a pair of switches to act as a single logical switch when forming link bundles. From the downstream switch/host point of view, it is connecting to a single switch.

In this example, you can see the Nexus is connecting to two Cumulus switches via LCAP. From the Nexus point of view, it is connecting to a single device. This provides greater redundancy.

Cumulus-1

net add interface eth0 ip address 192.168.1.10/24 
net add interface swp1-3 

net add bond peerlink bond slaves swp1,swp2 
net add interface peerlink.4094 clag backup-ip 192.168.1.11 
net add interface peerlink.4094 clag peer-ip 192.168.100.101 
net add interface peerlink.4094 clag sys-mac 44:38:39:FF:40:94 
net add interface peerlink.4094 ip address 192.168.100.100/24 

net add bond TEST-BOND bond slaves swp3 
net add bond TEST-BOND clag id 10 

interface eth0 
 address 192.168.1.10/24 

interface swp1 
interface swp2 
interface swp3 

interface TEST-BOND 
 bond-slaves swp3 
  clag-id 10 

interface peerlink 
 bond-slaves swp1 swp2 

interface peerlink.4094 
 address 192.168.100.100/24 
 clagd-backup-ip 192.168.1.11 
 clagd-peer-ip 192.168.100.101 
 clagd-sys-mac 44:38:39:FF:40:94

cumulus@cumulus:~$ net show clag status 

The peer is alive 
Our Priority, ID, and Role: 32768 50:00:00:03:00:02 primary 
Peer Priority, ID, and Role: 32768 50:00:00:04:00:02 secondary 
Peer Interface and IP: peerlink.4094 192.168.100.101 
 Backup IP: 192.168.1.11 (active) 
 System MAC: 44:38:39:ff:40:94 

CLAG Interfaces 
Our Interface      Peer Interface     CLAG Id   Conflicts              Proto-Down Reason 
----------------   ----------------   -------   --------------------   ----------------- 
       TEST-BOND   TEST-BOND          10        -                      -

Cumulus-2

net add interface eth0 ip address 192.168.1.11/24 
net add interface swp1-3 

net add bond peerlink bond slaves swp1,swp2 
net add interface peerlink.4094 clag backup-ip 192.168.1.10 
net add interface peerlink.4094 clag peer-ip 192.168.100.100 
net add interface peerlink.4094 clag sys-mac 44:38:39:FF:40:94 
net add interface peerlink.4094 ip address 192.168.100.101/24 

net add bond TEST-BOND bond slaves swp3 
net add bond TEST-BOND clag id 10 

interface eth0 
 address 192.168.1.11/24 

interface swp1 
interface swp2 
interface swp3 

interface TEST-BOND 
 bond-slaves swp3 
  clag-id 10 

interface peerlink 
 bond-slaves swp1 swp2 

interface peerlink.4094 
 address 192.168.100.101/24 
 clagd-backup-ip 192.168.1.10 
 clagd-peer-ip 192.168.100.100 
 clagd-sys-mac 44:38:39:FF:40:94 

cumulus@cumulus:~$ net show clag status 
The peer is alive 
Peer Priority, ID, and Role: 32768 50:00:00:03:00:02 primary 
Our Priority, ID, and Role: 32768 50:00:00:04:00:02 secondary 
Peer Interface and IP: peerlink.4094 192.168.100.100 
 Backup IP: 192.168.1.10 (active) 
 System MAC: 44:38:39:ff:40:94 

CLAG Interfaces 
Our Interface      Peer Interface     CLAG Id   Conflicts              Proto-Down Reason 
----------------   ----------------   -------   --------------------   ----------------- 
TEST-BOND   TEST-BOND          10        -                             -

Nexus

interface Ethernet1/1 
 channel-group 1 mode active 

interface Ethernet1/2 
 channel-group 1 mode active 

interface port-channel1

switch# show port-channel summary 

Flags:  D - Down        P - Up in port-channel (members) 
  		I - Individual  H - Hot-standby (LACP only) 
        s - Suspended   r - Module-removed 
        b - BFD Session Wait 
        S - Switched    R - Routed 
        U - Up (port-channel) 
        p - Up in delay-lacp mode (member) 
        M - Not in use. Min-links not met 
        -------------------------------------------------------------------------------- 
        Group Port-       Type     Protocol  Member Ports Channel 
        -------------------------------------------------------------------------------- 
        1     Po1(SU)     Eth      LACP      Eth1/1(P)    Eth1/2(P)

Thanks for the read

Suresh