Arista mlag

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Multi-Chassis Link Aggregation is the possibility with the Arista switch in order to utilize all interconnects in an active/active manner.

We will start from the below design :

with the the mlag configured between the 2 switch, all the path are in forward mode

CONFIGURATION PORT-CHANNEL

switch1#(config)#vlan 4094
switch1#(config)#name mlag
switch1#(config)#trunk group mlag
switch1#(config)#interface ethernet 47 - 48
switch1#(config-if-Et47-48)#description mlag
switch1#(config-if-Et47-48)#channel-group 100
switch1#(config-if-Po100)#switchport
switch1#(config-if-Po100)#switchport mode trunk
switch1#(config-if-Po100)#switchport trunk group mlag


switch2#(config)#vlan 4094
switch2#(config)#name mlag
switch2#(config)#trunk group mlag
switch2#(config)#interface ethernet 47 - 48
switch2#(config-if-Et47-48)#description mlag
switch2#(config-if-Et47-48)#channel-group 100
switch2#(config-if-Po100)#switchport
switch2#(config-if-Po100)#switchport mode trunk
switch2#(config-if-Po100)#switchport trunk group mlag

NO SPANNING-TREE FOR MLAG VLAN

switch1#(config)#no spanning-tree vlan 4094

switch2#(config)#no spanning-tree vlan 4094

CONFIGURATION INTERFACE PTP

switch1#(config)#interface vlan 4094
switch1#(config-if-Vl4094)#description mlag
switch1#(config)#ip address 100.100.100.0/31

switch2#(config)#interface vlan 4094
switch2#(config-if-Vl4094)#description mlag
switch2#(config)#ip address 100.100.100.1/31

CONFIGURATION MLAG

switch1#(config)#mlag configuration
switch1#(config-mlag)#domain-id mlag1
switch1#(config-mlag)#local-interface Valn4094
switch1#(config-mlag)#peer-address 100.100.100.1
switch1#(config-mlag)#peer-link Port-Channel100

switch2#(config)#mlag configuration
switch2#(config-mlag)#domain-id mlag1
switch2#(config-mlag)#local-interface Valn4094
switch2#(config-mlag)#peer-address 100.100.100.1
switch2#(config-mlag)#peer-link Port-Channel100

VERIFY

switch1#show mlag
....
MLAG Configuration:   
domain-id              :         mlag1
local-interface        :            Vlan4094
peer-address           :       100.100.100.1
peer-link              :     Port-Channel100
peer-config            :          consistent
                                            
MLAG Status:          
state                  :              Active
negotiation status     :           Connected
peer-link status       :                  Up
local-int status       :                  Up
system-id              :   xx:xx:xx:xx:xx:xx
dual-primary detection :            Disabled
                                            
MLAG Ports:           
Disabled               :                   0
Configured             :                   0
Inactive               :                   0
Active-partial         :                   0
Active-full            :                   0

CONFIGURATION DUAL-HOMED LINK

switch1#(config)#interface ethernet 45
switch1#(config-if-Et45)#channel-group 45 mode active
switch1#(config-if-Po45)#switchport mode trunk
switch1#(config-if-Po45)#switchport trunk group server
switch1#(config-if-Po45)#mlag 45

switch2#(config)#interface ethernet 45
switch2#(config-if-Et45)#channel-group 45 mode active
switch2#(config-if-Po45)#switchport mode trunk
switch2#(config-if-Po45)#switchport trunk group server
switch2#(config-if-Po45)#mlag 45

PECULIARITY

With the trunk group defined it is recommended to use the trunk group for all the vlans defined.

It is necessary to deploy on mlag port-channel all the vlans deployed

   interface Port-Channel 100
   description MLAG
   switchport mode trunk
   switchport trunk group mlag
   switchport trunk group server

CHECK CONFIG

switch1#show interface Port-Channel 45
............................
 Full-duplex, 20Gb/s 
  Active members in this channel: 2
  ... Ethernet45 , Full-duplex, 10Gb/s
  ... PeerEthernet45 , Full-duplex, 10Gb/s
 ..........................................

switch1#show mlag interface

mlag desc       state       local      remote     local/remote status
---------------------------------------------------------------------
45            Active-full     Po45      Po45              up/up  

the 2 sides must be up, otherwise it’s needed to check configuration on both sides (switch and server)

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