Etherchannel

We will begin with configuring the Etherchannel links between devices in the core/distribution layer of the network. Etherchannel, which allows many physical links to be bundled into a single logical link. The benefits of Etherchannel include the addition of bandwidth on each logical link, which can also be explained by two 100Mbit links in an Etherchannel group will mean the group has a total bandwidth of 200Mbit available. It also provides redundancy where if a single link goes down, the logical link does not necessarily go down, but it will reduce the total bandwidth available on the Etherchannel group until the broken link is restored. The following commands are an example of what is used on the network:

• #Switch(config): interface port-channel 1
• #Switch(config-intf): no switchport
• #Switch(config-intf): ip address 10.0.2.1 255.255.255.252

The above commands create an Etherchannel interface. The use of 'no switchport' allows an Etherchannel interface to run at layer 3 as oppose to layer 2. With layer 2 Etherchannel interfaces, you would omit the 'IP address' command. Currently, no Ethernet interfaces have been added to the port-channel group. The following commands cover adding the Ethernet interfaces to the Etherchannel group, which exist in the configuration files that will be used on devices:

• #Switch(config): interface FastEthernet0/1
• #Switch(config-intf): no switchport
• #Switch(config-intf): no ip address
• #Switch(config-intf): channel-group 1 mode active

• #Switch(config): interface FastEthernet0/2
• #Switch(config-intf): no switchport
• #Switch(config-intf): no ip address
• #Switch(config-intf): channel-group 1 mode active

The above commands configure the available Fast Ethernet interfaces as members of the Etherchannel group. 'channel-group 1' associates the interface with the corresponding port-channel interface, where the suffix modifier 'mode active' refers to negotiating different modes of Etherchannel, specifically choosing whether to actively or passively negotiate, PAgP (Port-Aggregation Protocol) or LACP (Link Aggregation Control Protocol).