Users Guide

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.
The benefit of supporting a dynamic LAG is that the Aggregator's server-facing ports can toggle between participating in the LAG or
acting as individual ports based on the dynamic information exchanged with a server NIC. LACP supports the exchange of messages on a
link to allow their LACP instances to:
• Reach agreement on the identity of the LAG to which the link belongs.
• Attach the link to that LAG.
• Enable the transmission and reception functions in an orderly manner.
• Detach the link from the LAG if one of the partner stops responding.
LACP Modes
The Aggregator supports only LACP active mode as the default mode of operation. In active mode, a port interface is considered to be not
part of a LAG but rather in an active negotiating state.
A port in active mode automatically initiates negotiations with other ports by sending LACP packets. If you configure server-facing ports
for LACP-based NIC teaming, LACP negotiations take place to aggregate the port in a dynamic LAG. If you do not configure server-facing
ports for LACP-based NIC teaming, a port is treated as an individual port in active negotiating state.
Link Aggregation
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