What is etherchannel ?

Etherchannel is a standard configuration IEEE 802.3AD. It is a link aggregation protocol, which enables multiple IDENTICAL links to be assembled into a single logical link.

Objectives:

• Increase bandwidth
• Increase fault tolerance

Requirements for 802.3AD :

Switch interconnection ports must be of same nature. i.e.:

WARNING: LINKS MUST BE FULL DUPLEX.

Definitions:

• HALF DUPLEX: is nano-directional communication
• FULL DUPLEX: is bidirectional communication

The 802.1Q configuration must be the same on both sides. i.e.:: If switch 0:

• VLANs 10,20,30 Then switch 1:
• VLANs 10,20,30

PAgP: Port Aggregation Protocol

PAgP is a Cisco proprietary protocol ettherchannel. This means it can only be configured between Cisco switches.

Cisco switch PAgP configuration commands :

Switch1> enable
Switch1# configure terminal
Switch1(conf)# interface range FastEthernet 0/1-2
Switch1(conf-if-range)# channel-group 1 mode desirable

INFO: Desirable mode must be set on the master switch (we must choose only one). On the slave switch(es), we must replace desirable by auto.

Definitions:

• desirable: Expects level 1 and 2 configuration from its neighboring switch.
• auto: Provides its level 1 and 2 configuration to its neighboring switch.

INFO: The 1 of channel-group, means aggregation group 1, we can set the desired value but the switches must have the same group.

Load Balancing :

Load balancing enables load balancing on etherchannel links.

Here's an example:

Switch1(conf)# port-channel load-balance ?
    dst-ip
    dst-mac
    src-ip
    src-mac
    src-dst-ip
    src-dst-mac

Switch1(conf)# port-channel load-balance src-ip

LACP: Link Aggregation Control Protocol

This is a non-Cisco proprietary etherchannel protocol => universal protocol.

LACP configuration :

Switch1(conf)# interface range FastEthernet 0/1-2
Switch1(conf-if-range)# channel-group 1 mode active

INFO: Active mode must be set on the master switch (we need to choose just one). On the slave switch(es), we must replace active by passive.