Administrator Guide

How the LACP is Implemented on an
Aggregator
The LACP provides a means for two systems (also called partner systems) to exchange information through
dynamic negotiations to aggregate two or more ports with common physical characteristics to form a link
aggregation group.
NOTE: A link aggregation group is referred to as a port channel by the Dell Networking OS.
A LAG provides both load-sharing and port redundancy across stack units. An Aggregator supports LACP for
auto-configuring dynamic LAGs. Use CLI commands to display LACP information, clear port-channel
counters, and debug LACP operation for auto-configured LAG on an Aggregator.
The Dell Networking OS implementation of LACP is based on the standards specified in the IEEE 802.3:
“Carrier sense multiple access with collision detection (CSMA/CD) access method and physical layer
specifications.”
LACP functions by constantly exchanging custom MAC protocol data units (PDUs) across local area network
(LAN) Ethernet links. The protocol packets are only exchanged between ports that you configure as LACP-
capable.
NOTE
: In Standalone, VLT, and Stacking modes, you can configure a maximum of 16 members in port-
channel 128. In PMUX mode, you can have multiple port-channels with up to 16 members per channel.
Uplink LAG
When the Aggregator power is on, all uplink ports are configured in a single LAG (LAG 128).
Server-Facing LAGs
Server-facing ports are configured as individual ports by default. If you configure a server NIC in standalone,
stacking, or VLT mode for LACP-based NIC teaming, server-facing ports are automatically configured as part
of dynamic LAGs. The LAG range 1 to 127 is reserved for server-facing LAGs.
After the Aggregator receives LACPDU from server-facing ports, the information embedded in the LACPDU
(remote-system ID and port key) is used to form a server-facing LAG. The LAG/port-channel number is
assigned based on the first available number in the range from 1 to 127. For each unique remote system-id
and port-key combination, a new LAG is formed and the port automatically becomes a member of the LAG.
All ports with the same combination of system ID and port key automatically become members of the same
LAG. Ports are automatically removed from the LAG if the NIC teaming configuration on a server-facing port
changes or if the port goes operationally down. Also, a server-facing LAG is removed when the last port
member is removed from the LAG.
Link Aggregation 527