LACP (802.3ad)
Link Aggregation Control Protocol
Step 1. Specify the interfaces that compose the EtherChannel group using the interface range interface global configuration mode command. The range keyword allows you to select several interfaces and configure them all together.
Step 2. Create the port channel interface with the channel-group identifier mode active command in interface range configuration mode. The identifier specifies a channel group number. The mode active keywords identify this as an LACP EtherChannel configuration.
Step 3. To change Layer 2 settings on the port channel interface, enter port channel interface configuration mode using the interface port-channel command, followed by the interface identifier. In the example, S1 is configured with an LACP EtherChannel. The port channel is configured as a trunk interface with the allowed VLANs specified.
Configure LACP on a range of interfaces using ‘active’ mode
LACP on a interfaces range using ‘Active’ mode
S1(config)# interface range FastEthernet 0/1 - 2 S1(config-if-range)# shutdown S1(config-if-range)# channel-group 2 mode active S1(config-if-range)# no shutdown S1(config-if-range)# exit
Configure the logical interface to become a trunk
Configuring the logical interface to become a ‘Trunk’
S1(config)# interface port-channel 2 S1(config-if)# switchport mode trunk S1(config-if)# exit
Configure the allowed VLANS on the Trunk
Allowing VLANS on the Trunk
S1(config)# interface port-channel 2 S1(config-if)# switchport trunk allowed vlan 1,2,20 S1(config-if)# exit
Configure Primary Root on Spanning Tree
At times, a Channel may not be operative because Spanning Tree Protocol placed some ports into blocking mode. It can be the case where such ports are the Gigabit ports and you want to restore them as the primary ports.
Configuring a Switch as the Primary Root in a Spanning Tree
S1(config)# spanning-tree vlan 1 root primary S1(config)# spanning-tree vlan 1 priority 24576 S1(config)# exit
LACP Complete Configuration example
S1(config)# interface range FastEthernet 0/1 - 2 S1(config-if-range)# shutdown S1(config-if-range)# channel-group 2 mode active Creating a port-channel interface Port-channel 2 S1(config-if-range)# exit S1(config)# interface port-channel 2 S1(config-if)# switchport mode trunk S1(config-if)# switchport trunk allowed vlan 1,2,20 S1(config-if)# exit