Cisco switches support two dynamic aggregation protocols:
- PAgP (Port Aggregation Protocol) – Cisco proprietary aggregating protocol.
- LACP (Link Aggregation Control Protocol) – IEEE standardized aggregation protocol, originally defined in 802.3ad.
PAgP and LACP are not compatible – both sides of an Etherchannel must use the same aggregation protocol.
EthernChannel – PAgP
It supports 2 Modes
- Desirable – actively attempts to form a channel
- Auto – waits for the remote switch to initiate the channelA PAgP channel will form
- desirable <- -> desirable
- desirable <- -> auto#interface range f0/22 – 24 #channel-protocol pagp #channel-group 1 mode desirable / auto
EtherChannel – LACP It has 2 Modes
- Active – actively attempts to form a channel
- Passive – waits for the remote switch to initiate the channelAn LACP channel will form
- active <- -> active
- active <- -> passive#interface range f0/22 – 24 #channel-protocol lacp
#channel-group 1 mode active / passive
Maximum of 8 active ports are supported in a single Etherchannel. LACP supports adding an additional 8 ports into the bundle in a standby state, to replace an active port if it goes down.
- LACP assigns a numerical port-priority to each port, to determine which ports become active in the Etherchannel. By default, the priority is set to 32768, and a lower priority is preferred. If there is a tie in system-priority, the lowest switch MAC address is preferred.#interface range f0/22 – 24 #lacp port-priority 100
#lacp system-priority 500
#show etherchannel summary #show port-channel summary