Juniper Networks EX2500 - Manual (Page 64)

EX2500 Ethernet Switch Configuration Guide
50 „ Link Aggregation Control Protocol
A port’s Link Aggregation Identifier (LAG ID) determines how the port can be
aggregated. The 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.
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.
By default, 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. Alternatively, you can configure the trunk ID
manually.
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 packets
known as LACP data units (LACPDUs) 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 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.
When the system is initialized, all ports by default are in LACP off mode and are
assigned unique admin keys. To make a group of ports aggregatable, you assign
them all the same admin key. Setting a port’s LACP mode to
active enables the port
to activate LACP negotiation. You can set the port’s LACP mode to passive to
reduce the amount of LACPDU traffic at the initial trunk-forming stage. All ports can
be set to
active , or to passive , or to any mix of settings. If all ports are set to passive ,
the partner switch can negotiate the link.
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)