CO5023 Link Aggregation

Issues with Redundancy To increase capacity on links between layers (access and distribution, for example) it can be useful to use redundancy However, STP will automatically block redundant links between switches This problem can be solved by combining physical links into one, logical link. This is the purpose of EtherChannel

Etherchannel Rules EtherChannel groups multiple ports into one physical link. Interfaces cannot be mixed – must all be Fast Ethernet or all be Gigabit Ethernet. Can link up to 8 ports together in an Etherchannel Can have up to 6 EtherChannels per switch.

Port Aggregation Protocol (PAgP) PAgP is CISCO proprietary and allows us to configure etherchannel ports in several modes. For an EtherChannel link to be established, the modes at each end need to be compatible (see chart opposite). Link Aggregation Control Protocol (LACP) is exactly the same except Desirable is called LACP Active and Auto is called LACP Passive.

Configuring link aggregation When configuring EtherChannel, speed and duplex settings must be the same for all ports at both ends. All interfaces in the channel must have the same VLAN settings. Create an interface group using: S(config)# int range interface-list S(config-if-range)channel-group 1 mode active S(config-if-range)int port-channel 1 S(config-if)switchport mode trunk …continue to configure channel as one interface

Verifying Etherchannels There are a few commands you can use to check the status of an EtherChannel: show interface port-channel !Not available on all switch models show etherchannel summary show etherchannel port-channel show interfaces etherchannel