3Com 3c17300 Implementation Guide - Page 27

Aggregated Links 29 Figure 4 An illegal aggregated link configuration Switch A AL 1 Switch B AL 2 Switch C AL 3 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.