Difference Between EtherChannel and Link Aggregation

Etherchannel is Ciscos propriety version of LACP.

Some even know that these are all words used to describe how to aggregate data across multiple physical links.

But many are confused when it comes to understanding the difference between each and when they should be used.

Link aggregation uses software to combine two to eight physical interfaces at layer 2 or layer 3 of the OSI model.

The goal is to have the multiple physical links act as a single logical interface.

EtherChannel was developed by a company Cisco acquired and integrated into Cisco network gear in the early 1990's.

It's become a generic term used that is often used interchangeably with the more correct term, link aggregation.

While link aggregation is the term used to describe the overall technology, EtherChannel is a Cisco proprietary method for actually configuring link aggregation on Cisco equipment.

There were originally three different ways to configure Cisco EtherChannel between switches.

One way was to statically set the connection on both sides.

The second was to negotiate the aggregation link using Cisco's proprietary Port Aggregation Protocol (PAgP).

And the third was to use 802.3ad, an open negotiation protocol also known as Link Aggregation Control Protocol (LACP).

It's important to note that Cisco is largely moving away from PAgP; newer switch operating systems, including the Nexus line, only support LACP as the link-aggregation negotiation protocol.

Other networking vendors such as Avaya, Juniper, and Huawei had their own proprietary link aggregation protocols that were similar to Cisco's PAgP, but all have since switched to the standards-based LACP.

Link aggregation (LAG) is simply a means to bundle multiple ethernet connections between a pair of switches to share the load. EtherChannel is Cisco's pre-standards model for doing so, which was originally inherited from the Kalpana acquisition. IEEE 802.3ad describes the standard way to aggregate links, including the Link Aggregation Control Protocol (LACP).

Link aggregation (LAG) is a partial implementation of the 802.3ad port aggregation standard. It bundles all of the controller’s distribution system ports into a single 802.3ad port channel, thereby reducing the number of IP addresses needed to configure the ports on your controller. When LAG is enabled, the system dynamically manages port redundancy and load balances access points transparently to the user.