Allied Telesis AT-S62 - Manual (Page 123)

AT-S62 Menus Interface User’s Guide
Section I: Basic Operations 123
❑ The switch can support up to six static trunks when LACP is
disable and three static trunks when LACP is enabled.
❑ The ports of a static trunk must be untagged members of the
same VLAN. A trunk cannot consist of untagged ports from
different VLANs.
❑ The switch selects the lowest numbered port in the trunk to
handle broadcast packets and packets of unknown destination.
For example, a trunk of ports 11 to 15 would use port 11 for
broadcast packets.
❑ You can create a port trunk of the ports in two expansion modules
in an AT-8500 Series switch, providing that the ports are of the
same medium type and have the same operating specifications.
LACP Trunk
Overview
An LACP (Link Aggregation Control Protocol) trunk is another type of
port trunk. Like a static trunk, it can increase the bandwidth between
two network devices by distributing the traffic load over multiple
physical links.
The advantage of an LACP trunk over a static port trunk is its flexibility.
While implementations of static trunks tend to be vendor specific, the
AT-8500 Series implementation of LACP is compliant with the IEEE
802.3ad standard. This makes it interoperable with equipment from
other vendors that also comply with the standard. This allows you to
create a trunk between an Allied Telesyn device and networking devices
from other manufacturers.
Another advantage is that ports in an LACP trunk can function in a
standby mode. This adds redundancy and resiliency to the trunk. Should
a link in a static trunk go down, the overall bandwidth of the trunk is
reduced and restoring it requires reestablishing the link or manually
modifying the trunk by adding another port to it. In contrast, an LACP
trunk can activate ports in a stand-by mode when an active link fails. The
automatic activation of standby ports allows the switch to maintain the
maximum possible bandwidth of the trunk.
For example, assume you create an LACP trunk of ports 11 to 20 on a
switch and the switch is using ports 11 to 18 as the active ports and ports
19 and 20 as reserve. If an active port loses its link, the switch
automatically activates one of the two reserve ports to maintain
maximum bandwidth of the trunk.
The main component of an LACP trunk is an aggregator. An aggregator
is a group of ports on the switch. The ports in an aggregator are further
grouped into one or more trunks, referred to as aggregate trunks.