Arista Networks Host-Link Aggregation

Setup your server side (I use Broadcom Advanced Control Suite) as you normally would.

On your new shiny Arista 7120T, this is what you need to do:

7120t enable
config t
int et1-4
channel-group 1 mode on

Then run: show int po1
Port-Channel1 is up, line protocol is up
Hardware is Port-Channel, address is xxxx.xxxx.xxxx
MTU is 9212 bytes, BW 40000000 Kbit
Full-Duplex, 40Gb/s
Active Members in this channel: 4
...Ethernet1 , Full-duplex, 10Gb/s
...Ethernet2 , Full-duplex, 10Gb/s
...Ethernet3 , Full-duplex, 10Gb/s
...Ethernet4 , Full-duplex, 10Gb/s
5 minutes input rate 0 bits/sec (0%), 0 packets/sec
5 minutes output rate 0 bits/sec (0%), 0 packets/sec
   0 packets input, 0 bytes
   Received 0 broadcasts, 0 multicast
   0 input errors
   0 packets output, 0 bytes
   Sent 0 broadcasts




Now you're cooking with gas :)


For switch to switch LACP: 


7124-SWB(config)#int et1-4
7124-SWB(config-if-Et1-4)#channel-group 1 mode passive
7148-SWA(config)#int et1-4
7148-SWA(config-if-Et1-4)#channel-group 1 mode active

Once the above sequence is entered and synchronization is complete, the ethernet interfaces 1-4 on each switch are bound to the port-channel.

If you're using another switch with your Arista, the config might be a bit different and you may need to try a few different configs to get it to work correctly.