Juniper Networks EX2500 manual 48 „ Link Aggregation Control Protocol

EX2500 Ethernet Switch Configuration Guide

NOTE: LACP implementation in the EX2500 switch does not support the Churn machine, an option used to detect if the port is operable within a bounded time period between the actor and the partner. Only the Marker Responder is implemented, and there is no marker protocol generator.

A port’s Link Aggregation Identifier (LAG ID) determines how the port can be aggregated. The Link Aggregation ID (LAG ID) is constructed mainly from the system ID and the port’s admin key, as follows:

„System ID—An integer value based on the switch’s MAC address and the system priority assigned in the CLI.

„Admin key—An integer value (13-65535) for the port that you can configure in the CLI. Each switch port that participates in the same LACP trunk group must have the same admin key value. The admin key is local significant, which means the partner switch does not need to use the same admin key value.

For example, consider two switches, an Actor (the EX2500 switch) and a Partner (another switch), as shown in Table 11.

Table 11: Actor vs. Partner LACP Configuration

Actor Switch	Partner Switch 1
Port 7 (admin key = 100)	Port 1 (admin key = 50)
Port 8 (admin key = 100)	Port 2 (admin key = 50)

In the configuration shown in Table 11, Actor switch port 7 and port 8 aggregate to form an LACP trunk group with Partner switch port 1 and port 2.

LACP automatically determines which member links can be aggregated and then aggregates them. It provides for the controlled addition and removal of physical links for the link aggregation.

Each port on the switch can have one of the following LACP modes:

„off (default)—The user can configure this port in to a regular static trunk group.

„active—The port is capable of forming an LACP trunk. This port sends LACPDU packets to partner system ports.

„passive—The port is capable of forming an LACP trunk. This port responds only to the LACPDU packets sent from an LACP active port.

Each active LACP port transmits LACP data units (LACPDUs), while each passive LACP port listens for LACPDUs. During LACP negotiation, the admin key is exchanged. The LACP trunk group is enabled as long as the information matches at both ends of the link. If the admin key value changes for a port at either end of the link, that port’s association with the LACP trunk group is lost.

48„ Link Aggregation Control Protocol