Port Trunking

Overview of port trunking

Port trunking allows you to assign up to eight physical links to one logical link (trunk) that functions as a single, higher-speed link providing dramatically increased bandwidth. This capability applies to connections between backbone devices as well as to connections in other network areas where traffic bottlenecks exist. A trunk group is a set of up to eight ports configured as members of the same port trunk. The ports in a trunk group do not have to be consecutive. For Example:

Conceptual Example: of port trunking

Conceptual Example: of port trunking

With full-duplex operation in a eight-port trunk group, trunking enables the following bandwidth capabilities:

Port connections and configuration

All port trunk links must be point-to-point connections between a switch and another switch, router, server, or workstation configured for port trunking. No intervening, non-trunking devices are allowed. It is important to note that ports on both ends of a port trunk group must have the same mode (speed and duplex) and flow control settings.

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Link connections

The switch does not support port trunking through an intermediate, non-trunking device such as a hub, or using more than onemedia type in a port trunk group. Similarly, for proper trunk operation, all links in the same trunk group must have the samespeed, duplex, and flow control.

Port security restriction

Port security does not operate on a trunk group. If you configure port security on one or more ports that are later added to a trunk group, the switch resets the port security parameters for those ports to the factory-default configuration.


CAUTION: To avoid broadcast storms or loops in your network while configuring a trunk, first disable or disconnect all ports you want to add to or remove from the trunk. After you finish configuring the trunk, enable or re-connect the ports.