Etherchannel(layer2-layer3)

EtherChannel is a port link aggregation technology or port-channel architecture used primarily on Cisco switches. It allows 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(wiki).

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There are two protocols in ether-channel:

  • PAGP (Cisco proprietary )

    • on

    • auto

    • desirable

  • LACP(Industry Standard)(802.3AD)

    • on

    • active

    • passive

To implement layer 2 PAGP:

SW1# conf t
SW1(config)#int range fa0/1-2
SW1(config-if)#channel-group 1 mode auto
SW1(config-if)#no shut
SW2# conf t
SW2(config)#int range fa0/1-2
SW2(config-if)#channel-group 1 mode desirable
SW2(config-if)#no shut

To implement layer 2 LACP:

SW1# conf t
SW1(config)#int range fa0/1-2
SW1(config-if)#channel-group 1 mode active
SW1(config-if)#no shut
SW2# conf t
SW2(config)#int range fa0/1-2
SW2(config-if)#channel-group 1 mode passive
SW2(config-if)#no shut

Layer 3 Etherchannel
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In layer3, we use virtual ip address in port channel to define PAGP:

SW1# conf t
SW1(config)#interface port-channel 1
SW1(config)#no switchport
SW1(config)#ip address 10.1.1.1 255.255.255.0
SW1(config)#interface range fa0/1-2
SW1(config-if)#channel-group 1 mode desirable
SW2# conf t
SW2(config)#interface port-channel 1
SW2(config)#no switchport
SW2(config)#ip address 10.1.1.2 255.255.255.0
SW2(config)#interface range fa0/1-2
SW2(config-if)#channel-group 1 mode auto
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