Allied Telesis AT-S63 - Manual (Page 135)

AT-S63 Management Software Menus Interface User’s Guide
Section I: Basic Features 135
Assume you selected source MAC address as the load distribution method
and that the switch needed to transmit over the trunk a packet with a
source MAC address that ended in 9. The binary equivalent of 9 is 1001,
making the last three bits of the address 001. An examination of the table
above indicates that the switch would use Port 8 to transmit the frame
because that port is mapped to the matching bits.
The same method is used for the two load distribution methods that
employ both the source and destination addresses. Only here the last
three bits of both addresses are combined by an XOR process to derive a
single value which is then compared against the mappings of the bits to
ports. The XOR rules are as follows:
0 XOR 0 = 0
0 XOR 1 = 1
1 XOR 0 = 1
1 XOR 1 = 0
As an example, assume that you had selected source and destination
MAC addresses for the load distribution method in our previous example,
and that a packet for transmission over the trunk had a source MAC
address that ended in 9 and a destination address that ended in 3. The
binary values would be:
9 = 1001
3 = 0011
Applying the XOR rules above on the last three bits would result in 010, or
2. A examination of the table above shows that the packet would be
transmitted from port 9.
Port trunk mappings on an AT-9400 Series switch can consist of up to
eight ports. This corresponds to the maximum number of ports allowed in
a static trunk and the maximum number of active ports in an LACP trunk.
(Inactive ports in an LACP trunk are not applied to the mappings until they
transition to the active status.)
You can assign different load distribution methods to different static trunks
on the same switch. The same is true for LACP aggregators. However, it
should be noted that all aggregate trunks within an LACP aggregator must
use the same load distribution method.
The load distribution methods assume that the final three bits of the source
and/or destination addresses of the packets from the network nodes are
varied enough to support adequate distribution of the packets over the
trunk ports. A lack of variation can result in one or more ports in a trunk
being used more than others, with the potential loss of a trunk’s efficiency
and performance.