Allied Telesis AT-S81 - Manual (Page 85)

AT-S81 Management Software User’s Guide
Section I: Using the Menus Interface 85
highest priorities are designated as the active ports in an aggregate trunk.
For example, if both 802.3ad-compliant devices support up to four active
ports and there are a total of eight ports in the trunk, the four ports with the
lowest priority settings are designated as the active ports, and the others
are placed in standby mode. If an active link goes down on a active port,
the standby port with the highest priority is automatically activated to take
its place.
The default value of a port’s priority number is equal to 1.
The selection of the active links in an aggregate trunk is dynamic. It
changes 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 it
to return to the active state by virtue of its having a higher priority, while the
port that replaced it is returned to the standby mode.
In the unusual event that you set this parameter to the same value for
some or all of the ports of an aggregate trunk, the selection of active ports
is based on port numbering. The lower the port number, the higher the
priority.
Two conditions must be met in order for a port that is a member of 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 it does continue to send LACPDU packets. If a port that is part
of a trunk group does not receive LACPDU packets, it functions as a
normal Ethernet port and forwards network packets along with LACPDU
packets.
LACP Trunk
Guidelines
Following are the guidelines for creating aggregators:
ˆ LACP must be activated on both the switch and the other device.
ˆ The other device must be 802.3ad-compliant.
ˆ The AT-8000/8POE Fast Ethernet switch supports up to eight active
ports in a trunk group at a time.
ˆ The switch supports a maximum of four trunks.
ˆ The ports of a trunk group must be of the same medium type: all
twisted pair ports or all fiber optic ports.
ˆ The ports of a trunk can be consecutive (for example ports 5-9) or
nonconsecutive (for example, ports 4, 8, 11, 20).
ˆ A port can belong to only one trunk group at a time.
ˆ The ports of an trunk group must be untagged members of the same
VLAN.