Select and synchronize bundle members
IEEE 802.1AX lets several full-duplex Ethernet links act as one Link Aggregation Group (LAG). With LACP, each side advertises its system and port identity, aggregation key and state. The exchanges let both sides identify compatible members and agree which can carry traffic in the bundle.
An active port initiates LACP exchanges. A passive port responds. Active and passive can form a bundle, as can two active sides. Two passive sides do not initiate negotiation. Matching mode is only one condition. The links also need compatible configuration and a consistent view of their partner.
What the bundle changes
The device can spread conversations across members, commonly by hashing packet fields. That raises aggregate capacity across multiple flows, but one flow normally stays on one member to preserve ordering. If a member goes down, the remaining members can carry traffic as long as the bundle still meets its minimum-link policy.
Try it in a lab
- Cable two links between compatible switches and configure both sides as LACP passive. Confirm that the links do not form a negotiated bundle.
- Change one side to active. Verify that both sides see the same partner on both members and that the members are forwarding in one bundle. Disconnect one link and check that the remaining link carries traffic if the configured minimum allows it.