2.1.e Implement and troubleshoot EtherChannel

EtherChannel is the Cisco term for the technology that enables the bonding of physical Ethernet links into a single logical link.

EtherChannel is a port link aggregation technology or port-channel architecture used primarily on Cisco switches. It allows the grouping of several physical Ethernet links to create one logical Ethernet link for the purpose of providing fault-tolerance and high-speed links between switches, routers, and servers. On different Cisco switches, it is possible to create logical connections that are made-up of different physical interface. It is necessary that these interfaces have the same speed. Most Cisco switches support max 64 EtherChannels. These interfaces do not have to be contiguous or even on the same module. Each channel must be made up of min 2, max 8 interfaces. The best is to use 2, 4, or 8 interfaces as that will lead to perfect load-balancing.

EtherChannel can either be configured manually, or can be dynamically negotiated via one of two protocols:

● Port Aggregation Protocol (PAgP) —Cisco’s proprietary aggregating protocol.

● Link Aggregation Control Protocol (LACP) —The IEEE standardized aggregation protocol, otherwise known as 802.3ad.

Switch > enable

Switch# configure terminal

Switch( config)# interface range fasttethernet0/ 1-2

Switch( config-if-range)# switchport mode access

Switch( config-if-range)# switchport access vlan 10

Switch(config-if-range)# channel-group 1 mode desirable \* use active to configure LACP

Show commands:

● show interfaces port-channel [channel-group -number]

● show etherchannel [channel-group-number] summary Verify commands:

● test etherchannel load-balance interface port-channel [#] ip [src] [dst]

Configuration errors usually occur because of mismatched parameters on the ports involved (i.e. different speeds, duplex, or different spanning tree port values, etc.). You can also generate errors within the configuration if you set the channel on one side to on and wait too long before you configure the channel on the other side. This causes spanning tree loops, which generates an error, and shuts down the port.

When an error is encountered while you configure EtherChannel, be sure to check the status of the ports after you correct the EtherChannel error situation. If the port status is errdisable, that means the port has been shut down by the software and will not come up again until you enter the set port enable command.

Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 1652-1665).  . Kindle Edition.