Allied Telesis AT-S79 - Manual (Page 69)

AT-S79 Management Software User’s Guide
Section I: Using the Menus Interface 69
manufacturer. For this reason static trunks are typically employed only
between devices from the same vendor. That is not to say that an Allied
Telesis layer 2 managed switch cannot form a static trunk with a device
from another manufacturer; but there is the possibility that the
implementations of static trunking on the two devices might not be
compatible.
Also, note that a static trunk does not provide for redundancy or link
backup. If a port in a static trunk loses its link, the trunk’s total bandwidth is
diminished. Although the traffic carried by the lost link is shifted to one of
the remaining ports in the trunk, the bandwidth remains reduced until the
lost link is reestablished or you reconfigure the trunk by adding another
port to it.
Static Port Trunk Guidelines
Following are the guidelines for creating a static trunk:
ˆ Allied Telesis recommends setting static port trunks between Allied
Telesis networking devices to ensure compatibility. While an
Allied Telesis device may be able to form a static trunk with a device
from another equipment vendor, it is possible that the implementation
of this feature on the two devices may not be compatible, resulting in
undesired switch behavior.
ˆ A static trunk can contain up to eight ports.
ˆ The ports of a static trunk must be of the same medium type. They can
be all twisted-pair ports or all fiber optic ports.
ˆ The ports of a trunk can be either consecutive (for example Ports 5-9)
or nonconsecutive (for example, ports 4, 8, 11, 20).
ˆ Before creating a port trunk, examine the speed, duplex mode, flow
control, and back pressure settings of all of the ports that will be
included in the trunk. Verify that the settings are the same for all ports
in the trunk. If these settings are not the same, then the switch will not
allow you to create the trunk.
ˆ After you have created a port trunk, a change to the speed, duplex
mode, flow control, or back pressure of any port in the trunk
automatically implements the same change on all the other member
ports.
ˆ A port can belong to only one static trunk at a time.
ˆ The ports of a static trunk can be untagged or untagged members of
the same VLAN.
The switch selects a port in the trunk to handle broadcast packets and
packets of unknown destination. The switch makes this choice based on a
hash algorithm, depending upon the source and destination MAC
addresses.