The Ether channel is a method of logically binding (port or link aggregation) the redundant links to provide high-speed data transfer. Which is developed by Cisco.

When multiple redundant links between switches are connected, the STP puts only one of the ports to the forwarding state and all other links are retained in the blocking state which significantly wastes bandwidth. By creating an EtherChannel, all the links are grouped together to form single logical link so it will act as a single logical link, therefore, no link will be blocked and also, its provide high-speed data without any error in the network.


Features of EtherChannel

EtherChannel features are as described below:

This support a maximum of 8 active ports depending on the port speed with a total bandwidth of 800 Mbit/s, 8 Gbits/s or 80 Gbits/s. 

Once EtherChannel is configured. all the ports that are part of the channel share the same MAC address. This makes the EtherChannel transparent to network users. Users only see a single connection (logical). 

when a physical link fails in a channel group. EtherChannel automatically redistributes the traffic with the remaining links. This provides high availability to the network. (Critical network such as servers. VolP, QoS). This automatic recovery takes less than one second.

STP with EtherChannel
After configuring EtherChannel. Spanning-tree treats all links between switches as one logical link and forwards the traffic to all connected ports. This provides load balancing in the switched network.

Manual and Dynamic EtherChannel

There are 3 ways of configuring the EtherChannel:

For manual channel configuration without using any form of negotiation and for configuring EtherChannel between different vendor switches. it is recommended to use either industry standard LACP or by performing manual channel configuration.

> Industry standard Dynamic channel negotiation using Link Aggregation Control Protocol (LACP).
> Cisco proprietary – Dynamic channel negotiation using Port Aggregation Protocol (PAgP) .

EtherChannel Terms 
Some of the EtherChannel terms are:

When multiple links are grouped into one single logical port, it is known as a port channel. 

To configure and assign a physical interface to EtherChannel, channel-group Commands are used.

Configuring and verifying Etherchannels
The two negotiation protocols use for aggregation are further classified as ‘Active’ and passive.

Port Aggregation Protocol (PAgP) is a Cisco proprietary protocol. PAgP has two channel modes. They are “Desirable” and “Auto”. 

> In the Auto mode, PAgP does not start any packet negotiation. 
> In the Desirable mode, it initiates the negotiation and tries to form a group (EtherChannel) with the other end.

LACP (802.3ad) 
Link Aggregation Protocol (LACP) is the IEEE open standard protocol. This has two channel modes, namely, ‘Active’ and ‘Passive’.

Active Mode 
It initiates the negotiation and tries to form a channel group(EtherChannel) with the other end.

Passive Mode 
‘it does not start Link Aggregation or packet negotiation.

A single logical channel is formed by grouping several physical ports by means LACP.

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