Allied Telesis AT-9000/28, User Manual

Page: 458 / 1278

Chapter 34: Link Aggregation Control Protocol (LACP)
458 Section V: Port Trunks
ports, and the others are placed in the standby mode. If an active link goes
down on a active port, the standby port with the next highest priority is
automatically activated to take its place.
The selection of the active links in an aggregate trunk is dynamic and will
change as links are added, removed, lost or reestablished. For example, if
an active port loses its link and is replaced by another port in the standby
mode, the reestablishment of the link on the originally active port causes
the port to return to the active state by virtue of having a higher priority
value than the replacement port, which returns to the standby mode.
A port’s priority value is not adjustable.
Two conditions must be met in order for a port in an aggregate trunk to
function in the standby mode. First, the number of ports in the trunk must
exceed the highest allowed number of active ports and, second, the port
must be receiving LACPDU packets from the other device. A port
functioning in the standby mode does not forward network traffic, but does
continue to send LACPDU packets. If a port that is part of an aggregator
does not receive LACPDU packets, it functions as a normal Ethernet port
and forwards network packets along with LACPDU packets.
Load Distribution
Methods
The load distribution method determines the manner in which the switch
distributes the traffic across the active ports of an aggregate trunk. The
method is assigned to an aggregator and applies to the aggregate trunk in
it. For further information, refer to “Load Distribution Methods” on
page 440.
Guidelines
Here are the LACP guidelines:

LACP must be activated on both the switch and the other device.

The other device must be 802.3ad-compliant.

An aggregator can consist of any number of ports.

The switch supports up to eight active ports in an aggregate trunk at a
time.

The switch can support up to a total of 32 static and LACP aggregate
trunks at a time. An LACP trunk is countered against the maximum
number of trunks only when it is active.

The ports of an aggregate trunk must be the same medium type: all
twisted pair ports or all fiber optic ports.

The ports of a trunk can be consecutive (for example ports 5 to 9) or
nonconsecutive (for example, ports 4, 8, 11, 20).

A port can belong to only one aggregator at a time.

A port cannot be a member of an aggregator and a static trunk at the
same time.

The ports of an aggregate trunk must be untagged members of the
same VLAN.