LAG a.k.a Link aggregation is a technology where multiple links from a switch chassis were bundled together and connected to multiple links on the neighbor switch chassis to provide increased bandwidth capacity. Multiple links combined act as one logical link and in case any physical link fails the traffic is automatically shifted onto another link in bundle hence providing some redundancy. However in LAG in case a switch chassis goes faulty then there is no redundancy.
MLAG is an enhancement of LAG where the ports from different switch chassis are bundled together to act as a single logical link. This also provides active/active uplinks with no layer 2 loops. MLAG switch is much similar to VPC feature in Cisco Nexus but MLAG being non-proprietary.
MLAG Domain – A pair of physical switches
MLAG peer – A single switch within an MLAG domain
MLAG peer-link – Ethernet physical link between MLAG peers required to synchronize state between MLAG peers and carry user data
MLAG member port – One or more user-facing physical ports that forms an MLAG
MLAG port-channel – This is a combined user-facing port-channel between MLAG peers consisting of MLAG member ports on both MLAG peers
MLAG VLAN – A VLAN used exclusively on the MLAG peer-link, in order to aid control-plane communication between MLAG peers.
Multi-Chassis LAG (MLAG) configuration steps are as below:
Step 1: Configure the peer link.
There should be minimum of two ports for redundancy and under normal circumstances peer link shouldn’t be used to carry any data-traffic.
Switch1(config)#interface eth 1-2
Switch1(config-if-Et1-2)#channel-group 10 mode active