3Com SuperStack 3C17300 Implementation Manual page 27

Figure 4 An illegal aggregated link configuration
To make this configuration work you need to have two aggregated links
defined on Switch A, one containing the member links for Switch B and
the other containing those for Switch C.
When using an aggregated link, note that:
To gather statistics about an aggregated link, you must add together
the statistics for each port in the aggregated link.
If you wish to disable a single member link of an aggregated link, you
must first physically remove the connection to ensure that you do not
lose any traffic, before you disable both ends of the member link
separately. If you do this, the traffic destined for that link is distributed
to the other links in the aggregated link.
If you do not remove the connection and only disable one end of the
member link port, traffic is still forwarded to that port by the
aggregated link port at the other end. This means that a significant
amount of traffic may be lost.
Before removing all member links from an aggregated link, you must
disable all the aggregated link member ports or disconnect all the
links, except one — if you do not, a loop may be created.
Traffic Distribution and Link Failure on Aggregated Links
To maximize throughput, all traffic is distributed across the individual links
that make up an aggregated link. Therefore, when a packet is made
available for transmission down an aggregated link, a hardware-based
traffic distribution mechanism determines which particular port in the link
should be used; this mechanism uses the MAC address. The traffic is
distributed among the member links as efficiently as possible.
Switch A
AL 1
Switch B
AL 2
Switch C
AL 3
Aggregated Links 29