Link aggregation control protocol (LACP) is the protocol that is providing a mechanism for two Layer-2 network devices to negotiate over bundling multiple Layer-1 links into a single, logical interface for the sake of easy configuration and monitoring. These types of interfaces are defined in 802.1AX
Many vendors have different words for describing this concept across their own operating systems:
- LACP can make Port-Channels (Arista/Cisco)
- LACP can make Bridge-Aggregation interfaces (HPE Comware)
- LACP can make Link-Aggregation bundles (Brocade/Foundry)
- LACP can make a NIC Team (VMWare ESX/Microsoft Windows Server)
- LACP can make an Aggregate Ethernet interface (Palo Alto Networks NGFW/Juniper)
- LACP can make a bond network interface (Linux)
The essential parts for making an LACP bundle work (without getting specific about per-vendor implementations), are ensuring that the aspects of LACP bundles exchanged during the LACP negotiation phase match on both sides.
LACP Mode
The LACP has a few different modes for operating the links together, particularly the modes are:
- Auto / Active
- This configured device moves into an active state where the device begins sending PDUs for protocol negotiation.
- Passive
- This causes the connected device to enter a passive mode
- The passive mode turns off active negotiation PDUs being sent from this device
- The other device on the other end of the cable is responsible for starting negotiation
- Mode “on”
- Forces the bundle up
- Works only when the other device is also configured to mode ‘on’
LACP Load Sharing/Balancing
Another part of this protocol is to exchange information that determines how the connected switches choose which port in the bundle to use for a particular packet or flow. The basic methods include:
Related Links External
- https://standards.ieee.org/standard/802_3-2002.html
- https://standards.ieee.org/standard/802_3ad-2000.html
- https://en.wikipedia.org/wiki/Link_aggregation#802.1AX