> # Prerequisites for PortChannels

> Before configuring a PortChannel, consider the following guidelines:

> - Configure the PortChannel across switching modules to implement redundancy on switching module reboots or upgrades.
> - Ensure that one PortChannel is not connected to different sets of switches. PortChannels require point-to-point connections between the same set of switches.

> Note On switches with Generation 1 switching modules, or a combination of Generation 1 and Generation 2 switching modules, you can configure a maximum of 128 PortChannels. On switches with only Generation 2 switching modules, or Generation 2 and Generation 3 switching modules, you can configure a maximum of 256 PortChannels.

> If you misconfigure PortChannels, you may receive a misconfiguration message. If you receive this message, the PortChannel’s physical links are disabled because an error has been detected.

> A PortChannel error is detected if the following requirements are not met:

> - Each switch on either side of a PortChannel must be connected to the same number of interfaces.
> - Each interface must be connected to a corresponding interface on the other side .
> - Links in a PortChannel cannot be changed after the PortChannel is configured. If you change the links after the PortChannel is configured, be sure to reconnect the links to interfaces within the PortChannel and reenable the links.

> If all three conditions are not met, the faulty link is disabled.

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