3Com 3C17300-US - SuperStack 3 Switch 4226T, Implementation Manual

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28 C
HAPTER
2: O
PTIMIZING
B
ANDWIDTH
Figure 3 Aggregated
—
Link Example
■
LACP Pre-Configured Aggregations — If you need to know which
aggregated link is associated with which device in your network you
can use a LACP pre-configured aggregation. This allows you to
manually configure the MAC address of a particular partner device
(called the partner ID) against a specified aggregated link. LACP will
then automatically determine the port membership for that
aggregated link.
The aggregated link may be manually configured with appropriate
configuration settings, such as VLAN membership, to match the
partner device.
■
LACP Automatic Aggregations — If LACP detects at least two active
ports sharing the same partner device, and if no matching
pre-configured aggregated links exist, LACP will automatically assign a
free un-configured aggregated link to form an aggregated link with
the partner device. The aggregated link will inherit its configuration
from the first port originally detected against the partner device.
If you have an existing single port connection between two devices,
this automatic behavior allows quick and easy addition of extra
bandwidth by simply adding an extra physical link between the units.
The Spanning Tree costs for a port running LACP is the cost assigned for
an aggregated link running at that speed. As required by the IEEE
802.3ad standard, no changes in cost are made according to the number
of member links in the aggregated link.
By default LACP is disabled on all 10/100/1000BASE-T and GBIC or SFP
Switch ports.
Switch A
Switch B
Switch C
Aggregated Link
Aggregated Link
dua1730-0bAA03.book Page 28 Monday, July 11, 2005 11:14 AM