Allied Telesis AT-S39 User Manual
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Now assume that you configured the port trunk on Switch #1 for SA load
distribution. The switch might distribute the load as follow:
For example, when Workstation B sends a packet to the server, Switch #1
will use Port 14 of the trunk to transmit it to Switch #2.
An assignment of a source MAC address to a port trunk remains active as
long as the source node remains active. If the MAC address times out,
the assignment is dropped. Should the source node become active
again and need to transmit a packet over the trunk, a new assignment is
made, either to the same port or to a different port in the trunk.
It should be noted that packets sent back from the destination node to
the original source node may travel the same or a different data link in
the trunk.
As a general rule, the SA load distribution method is useful in situations
where the number of source nodes equals or is greater than the number
of data links in the trunk.
So when would the SA method be inappropriate? Let’s look back again
at the example in Figure 20. Let’s assume that you configured Switch #2
also for SA load distribution. The result would be that the switch would
use only one data link in the trunk to send packets back to Switch #1,
because there is only one source, a Gigabit Ethernet server, connected to
Switch #2. Since there is only one source, only one data link is used. So
obviously the SA method is not appropriate when there are fewer source
nodes than data links.
Table 1 Switch #1 Load Distribution
Source Workstation
Source MAC
Address
Trunk Port
A
00A0EE 2313A3
13
B
00A134 1A9032
14
C
00A301 9083B2
15
D
001B21 87C6D6
14