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Introduction and Configurations of Arista MLAG

December 31, 2019 ,
Talking about Arista MLAG first, Arista’s Multichassis Link Aggregation (MLAG) feature removes this bottleneck and allows the utilization of all interconnects in an active/active mode. In order to utilize all interconnects in an active/active manner, Arista EOS now supports the MLAG feature. This allows one to interconnect two Arista 7000 Family switches and use them as one logical switch for the purpose of L2 protocols such as STP or LACP.

 Below is the sample topology showing the MLAG use in the Arista Network ( Datacenter environment). Hope the below mentioned network topology helps to understand about the MLAG.

Arista MLAG
Fig 1.1-Arista Networks MLAG
Features of using MLAG in the datacenter environment
  • Up to 16 1GbE or 10GbE ports can be aggregated together and spread across the two switches
  • Two Arista 7000 Family network switches can be in an MLAG pair, increasing your network scalability by 2X
  • Allows you to design non-blocking networks
  • Maintains same level of resiliency with redundant paths available at all times
  • No proprietary protocol used to connect an MLAG pair to servers or other switches. Interconnect to other switches or servers can use static LAG or IEEE 802.3ad LACP
  • Spanning Tree Protocol can still be used in conjunction with MLAG to detect and handle any misconfigurations
  • No wasted bandwidth with uplinks in Spanning Tree Blocking state
Lets talk about the basic configurations on these switches ( Sample Configurations)


Configuration on Arista Switch 1
!
vlan 4094
   trunk group MLAG_Peer
!
interface Vlan4094
   ip address 172.17.255.1/30
!
mlag configuration
   domain-id MLAG1
   local-interface Vlan4094
   peer-address 172.17.255.2
   peer-link Port-Channel1
!
interface Port-Channel1
   switchport mode trunk
   switchport trunk group MLAG_Peer
!
interface Ethernet47
   channel-group 1 mode active
!
interface Ethernet48
   channel-group 1 mode active
!
interface Port-Channel200
   switchport mode trunk
   mlag 200
!
interface Ethernet10
  switchport mode trunk
  channel-group 200 mode active
!

The port-channle and the IP addresses uses in the above mentioned configuration is just for the sample configuration and has no relevance with any of the enterprise network.

Configuration on Arista Switch 2
!
vlan 4094
   trunk group MLAG_Peer
!
interface Vlan4094
   ip address 172.17.255.2/30
!
mlag configuration
   domain-id MLAG1
   local-interface Vlan4094
   peer-address 172.17.255.1
   peer-link Port-Channel1
!
interface Port-Channel1
   switchport mode trunk
   switchport trunk group MLAG_Peer
!
interface Ethernet47
   channel-group 1 mode active
!
interface Ethernet48
   channel-group 1 mode active
!
interface Port-Channel200
   switchport mode trunk
   mlag 200
!
interface Ethernet10
  switchport mode trunk
  channel-group 200 mode active
!