Reference Guide

Link aggregation control protocol
Group Ethernet interfaces to form a single link layer interface called a LAG or port-channel. Aggregating multiple links between physical
interfaces creates a single logical LAG, which balances trac across the member links within an aggregated Ethernet bundle and increases
the uplink bandwidth. If one member link fails, the LAG continues to carry trac over the remaining links.
You can use LACP to create dynamic LAGs exchanging information between two systems (also called Partner Systems) and automatically
establishing the LAG between the systems. LACP permits the exchange of messages on a link to:
• Reach an agreement on the identity of the LAG to which the link belongs.
• Move the link to that LAG.
• Enable the transmission and reception functions.
LACP functions by constantly exchanging custom MAC PDUs across LAN Ethernet links. The protocol only exchanges packets between
ports you congure as LACP-capable.
Modes
A LAG includes three conguration modes — on, active, and passive.
On Sets the Channeling mode to Static. The interface acts as a member of the static LAG.
Active Sets the interface in the Active Negotiating state. LACP runs on any link congured in this mode. A port in Active
mode automatically initiates negotiations with other ports by using LACP packets. A port in Active mode can set up
a port-channel (LAG) with another port in Active mode or Passive mode.
Passive Sets the interface in an Inactive Negotiating state, but LACP runs on the link. A port in Passive mode also responds
to negotiation requests (from ports in Active mode). Ports in Passive mode respond to LACP packets. A port in
Passive mode cannot set up a LAG with another port in Passive mode.
• There is no dual-membership in static and dynamic LAGs:
– If a physical interface is a part of a static LAG, the channel-group id mode active command is rejected on that interface.
– If a physical interface is a part of a dynamic LAG, the channel-group id command is rejected on that interface.
• You cannot add static and dynamic members to the same LAG.
• There is a dierence between the shutdown and no interface port-channel commands:
– The shutdown command on LAG xyz disables the LAG and retains the user commands.
– The no interface port-channel channel-number command deletes the specied LAG, including a dynamically created
LAG. The interfaces restore and are ready for conguration.
• A maximum of 128 port-channels with up to 16 members per channel are allowed.
Conguration
LACP is enabled globally by default. You can congure aggregated ports with compatible active and passive LACP modes to automatically
link them.
1 Congure the system priority in CONFIGURATION mode (1 to 65535; the higher the number, the lower the priority; default 32768).
lacp system-priority priority-value
2 Congure the LACP port priority in INTERFACE mode (1 to 65535; the higher the number, the lower the priority; default 32768).
lacp port-priority priority-value
3 Congure the LACP rate in INTERFACE mode (default normal).
lacp rate [fast | normal]
Layer 2
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