Core issue
An incorrect channel mode configuration on a switch connected to a Catalyst 2900XL or 3500XL switch results in the inability to bring up an EtherChannel.
Resolution
The Catalyst 2900XL and 3500XL switches do not support Port Aggregation Protocol (PAgP) or Link Aggregate Control Protocol (LACP). Therefore, the channel mode of the connected devices must be set to on mode in order for a channel to come up. If the channel mode on the connected switch is set to the default value of auto or desirable, the channel does not come up.
To verify the channel mode on the connected switch, issue these commands:
- For Catalyst OS (CatOS), issue the show port channel command.
- For Cisco IOS , issue one of these commands (depending on the platform and Cisco IOS version):
For detailed instructions about the configuration of an EtherChannel on various switches connected to the Catalyst 2900XL and 3500XL switches, as well as configuration on the XL switches, refer to the documents listed in the Configuring EtherChannel and 802.1Q Trunking Between Catalyst 2900 XL/3500 XL and Catalyst 2950 section of EtherChannel.
