Port Aggregation Protocol

Port Aggregation Protocol (PAgP) is a Cisco Systems proprietary networking protocol, which is used for the automated, logical aggregation of Ethernet switch ports, known as an etherchannel. This means it can only be used between Cisco switches and/or switches from licensed vendors. A similar purpose protocol known as LACP, released by the IEEE known as 802.3ad, is an industry standard and is not tied to any specific vendor.

PAgP can be configured on a Cisco switch to operate in three different modes.
- auto : Passive negotiation of the channel.
- desirable : Active negotiation of the channel.
- on : No protocols are used, it assumes the other side has also enabled link aggregation.

On Cisco network devices running CatOS, a single switch module may only be configured to run in either LACP or PAgP modes. Cisco devices that run IOS (native and/or non-hybrid mode boxes) support individual port configuration for LACP and are not restricted to per module settings as with CatOS.

Limitations

A limitation of Port Aggregation Protocol is that all the physical ports in the aggregation group must reside on the same switch. Avaya's SMLT protocol removes this limitation by allowing the physical ports to be split between two switches in a triangle configuration or 4 or more switches in a mesh configuration.

External links

• Cisco Systems documentation