3Com 3C17203 - SuperStack 3 Switch 4400, Implementation Manual

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30 C
HAPTER
2: O
PTIMIZING
B
ANDWIDTH
configured as 100BASE-TX and they are operating in full duplex, the
potential maximum bandwidth of the connection is 800 Mbps.
Figure 1 Switch units connected using an aggregated link
.
3Com recommends that you use IEEE 802.3ad LACP automatic
aggregations rather than manual aggregations to ensure maximum
resilience on your network. Using manual aggregations to connect to a
stack could result in network loops if the cascade fails. By default, LACP is
disabled on all Switch ports.
How 802.3ad Link
Aggregation
Operates
Your Switch supports IEEE Std 802.3-2002 (incorporating 802.3ad)
aggregated links which use the Link Aggregation Control Protocol
(LACP). LACP provides automatic, point-to-point redundancy between
two devices (switch-to-switch or switch-to-server) that have full duplex
connections operating at the same speed.
By default, LACP is disabled on all Switch ports. If LACP is enabled on all
Switch ports, this means that your Switch will detect if there is more than
one connection to another device and will automatically create an
aggregated link consisting of those links.
If a member link in an aggregated link fails, the traffic using that link is
dynamically reassigned to the remaining member links in the aggregated
link.
Figure 2 shows the simplest case: two member links, that is the
physical links, form an aggregated link. In this example, if link 1 fails, the
data flow between X and B is remapped to physical link 2. The
re-mapping occurs as soon as the Switch detects that a member link has
failed — almost instantaneously. As a result, aggregated link
configurations are extremely resilient and fault-tolerant.