Link Aggregation Control Protocol (LACP) negotiates an EtherChannel between neighboring switches by comparing configuration parameters. As an IEEE 802.3ad standard, it supports links between equipment from different vendors, unlike Cisco-proprietary PAgP. section 16.2.1 section 16.5
Key operational points:
- Use active mode to actively negotiate; passive mode waits for a neighboring LACP device. An active/passive pairing forms the channel. section 16.5
- LACP combines physical links into one logical link, allowing member links to remain in STP forwarding without creating a Layer 2 loop. section 16.5
- LACP supports up to 16 links, although only eight operate simultaneously; additional links remain available as standby links. section 16.5
- Assign member ports with channel-group group-number mode active or passive, then configure access or trunk settings on the logical port-channel interface. section 16.5
Active/passive trunk EtherChannel
Configure SW1 interfaces G0/0–G0/1 with channel-group 1 mode active and SW2 interfaces with channel-group 1 mode passive. Apply switchport mode trunk to Po1 on both switches. Verify show etherchannel summary reports LACP and both member ports with P status.
