Introduction

The EtherChannel allows you to group (aggregate) several ports into one.

The phrase "Link Aggregate" often comes up in French technical jargon (Aggregation – Grouping elements). I would use the terminology "EtherChannel" because all CISCO documentation is in English and it is important to become familiar with English terminology.

Knowing that a good sketch is better than a long speech, let's go straight back to the subject:

We have a link between two switches at 100Mbps. Our switch only has ports in Fast Ethernet (100 Mbps).

We need a 400Mb/s connection. We just have to add three links between these switches!

Unfortunately my links don't want to go up… What for? Because our equipment considers this to be a network loop! The STP protocol retains only a functional interface. How do I do that?

Setting up etherChannel 🙂

The EtherChannel allows you to group physical interfaces into a group. This group will be seen as a virtual interface by our switch.
To put it simply, we have 8 Ports (4 right and 4 left) it must be:

– All identical (Ethernet or Fast Ethernet or GigaBitEthernet etc…)
– Equal number on both sides of our Etherchannel.
– The ports that want to aggregate the same switch is in the same "Channel-group"

If one of the links falls, the EtherChannel continues on 3 links!

The EtherChannel is limited to 8 interfaces

There are two Etherchannel protocols:

PAgP (Port Aggregation Protocol)

– CISCO Owner
– Two modes: (Auto / Desirable)

LACP (Link Aggregation Control Protocol)

– IEEE 802.3ad Standard
– Two modes: (Active/Passive)

Switch (config-if) channel-group 1 mode?

active Enable LACP unconditionally
auto Enable PAgP only if a PAgP device is detected
desirable Enable PAgP unconditionally
on Enable Etherchannel only
passive Enable LACP only if a LACP device is detected

PAgP Configuration (CISCO)

Switch (config)#interface FastEthernet range 0/1 -4
Switch (config-range)#channel-group 1 mode [ on | Desirable | Auto ]
Switch (config-range) #exit

Switch (config)#interface port-channel 1
Switch (config-if)#description VERS-SWITCH-B
Switch (config-if)#switchport trunk mode
Switch (config-if)#switchport trunk encapsulation dot1q

LACP Configuration (IEEE)

Switch (config)#interface FastEthernet range 0/1 -4
Switch (config-range)#channel-group 1 mode [ on | Active | Passive ]
Switch (config-range)#channel-protocol lacp
Switch (config-range) #exit

Switch (config)#interface port-channel 1
Switch (config-if)#description VERS-SWITCH-B
Switch (config-if)#switchport trunk mode
Switch (config-if)#switchport trunk encapsulation dot1q

The default protocol is pagP. To use the LACP protocol, we just have to tell our equipment with the lacp channel-protocol command

Balancing Load

In order to balance the load on the physical interfaces participating in the EtherChannel, our Switches can distribute the frames to send according to several parameters:

– src-mac — MAC source address — Bits
– dst-mac — Mac destination address — Bits
– src-dst-mac — MAC address source and destination — XOR
– src-ip — IP source address — Bits
– dst-ip — IP address destination — Bits
– src-dst-ip —IP source and destination address (Default) — XOR
– src-port —Port source — Bits
– dst-port — Port destination — Bits
– src-dst-port —Source and destination port — XOR

The load balancing method changes this as follows:

Switch (config) port-channel load-balance src-dst-ip

Mind Map

Noël NICOLAS