Fast EtherChannel (FEC) and Gigabit EtherChannel (GEC) port groups act as single, logical ports for high-bandwidth connections between switches, or between switches and servers. There are two different types of port groups:
source-based forwarding port groups
destination-based forwarding port groups.
Source-based forwarding port groups distribute packets forwarded to the group based on the source address of incoming packets. You can configure a maximum of eight ports in a source-based forwarding port group. Source-based forwarding is enabled by default.
Destination-based port groups distribute packets forwarded to the group based on the destination address of incoming packets. You can configure an unlimited number of ports in a destination-based port group.
You can create a maximum of 12 port groups. All ports in each group must be of the same type. For example, they must be all source-based or all destination-based. But, you can have source-based port groups and destination-based port groups. You can independently configure port groups that link switches, but you must consistently configure both ends of a port group.
The switch treats the port group as a single logical port. Therefore, when you create a port group, the switch uses the configuration of the first port for all ports added to the group. If you add a port and change the forwarding method, it changes the forwarding for all ports in the group. After the group is created, if you change Spanning Tree Protocol (STP) or VLAN membership parameters for one port in the group, this automatically changes the parameters for all ports. Each port group has one port that carries all unknown multicast, broadcast, and STP packets.
Complete these steps in order to configure port channeling on the Catalyst 2900XL and 3500XL series switches:
Enter interface configuration mode, and enter the first port to be added to the group when you issue the interface [type] slot/port command.
Issue the port group [group_number] destribution destination command in order to assign the port to a group number with destination-based forwarding.
Issue the interface [type] <mod/port> command in order to enter the second port to be added to the group. Issue the port group [group_number] distribution destination command in order to assign the port to a group number with destination-based forwarding. Repeat steps 4 and 5 for all ports in the first port group, where the group number is 1, or another number that you choose.
Issue the end command in order to return to privileged EXEC mode.
Issue the show running-config command in order to verify your entries.
Repeat the previous steps for each EtherChannel (port) group.
Note: The steps listed are for the Catalyst 2900XL and 3500XL series switches. Configuration steps for EtherChanneling on the Catalyst 2950 and 3550 are similar, but there are some significant differences. For example, unlike the XLs, EtherChannels are referred to as channel groups, and it is critical to pay attention to the EtherChannel mode, for example, desirable, auto, on, off, and passive. Port Aggregation Protocol (PAgP) and Link Aggregation Control Protocol (LACP), which are types of EtherChannels, are also options.