LACP (Link Aggregation Control Protocol) negotiates and maintains link bundles. Both ends must agree on the bundle before forwarding.
LACP modes:
- Active: Sends LACP packets to initiate negotiation
- Passive: Waits for the other side to initiate
At least one side must be active. Both passive means no bundle forms.
interface range GigabitEthernet0/1-2 channel-group 1 mode active
This creates Port-channel1. LACP detects failures faster than physical link detection, typically within seconds.