Lag and its different variations

Lag increases the bandwidth between two nodes by grouping different ports together.

Increases performance as the load can be shared between the two links.

Also provides improved resiliency as the traffic can be switched from one port to another in the event of a failure of one of the ports.













Lags can be configured on both the access and the network ports. The speed and duplex settings of all the ports in the lag should match, autonegotiation should be disabled or should be configured as limited.

For 10 gig ports the X-GIG setting of the ports should be same.

Threshold action when down is specified the lag will be brought down only when the number of links active falls below the thresold.
ie if the threshold configured is 4, so the lag will be brought down when the number of active links in the lag is 4, the lag is up when the number of links is 5.

Dynamic Cost:- If the cost of the link is 100, and if we bundle 4 links the cost od the lag will be 25 and then if one of the link goes down the cost will 100/3=33 approx.

Configured address/Hardware Address;- The first 3 bits match the first 3 bits of the chassis mac address the last 3 bits resembles the lag number so if the lag used is 1 it should be 00:01:41.

Lacp

Lag can also be configured by using a protocol such as LACP.
These LACP messages every 1 sec if lacp is configured as fast or every 30 sec if lacp is configured as a slow.
Uses slow protocol destination mac 01:80:C2:00:00:02
Self is known as the actor and the peer is known as the partner.

Three parameters uniquely identify a LAG instance to the

local node:

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subsequent LAGs)

LACP key (default 32768 for first LAG, increase by one for

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System ID (derived from base MAC address; show chassis)

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x

Passive will only start sending lacp packets once it starts receiving from the active side.
System priority (default 32768; configure system lacp-systempriority)