Alcatel Omni Switch/Router, User Manual

Page: 253 / 1100

Duplicate MAC Address Support
Page 9-31
If your network supports duplicate
MAC
addresses, there may be a significant performance
impact due to the following reasons:
• A
MAC
address is usually stored only in the
CAM
of the switching module where its desti-
nation address is located. If duplicate
MAC
addresses are treated as separate addresses,
then the same
MAC
address may have to be stored in the
CAM
of multiple switching
modules, not just the module that originally learned the address.
• Every duplicate
MAC
address becomes a
CAM
table entry, so there will be less room in the
CAM
for other entries to be learned. Since up to 32 duplications of a single
MAC
address
are possible, this
CAM
can become crowded with these duplicate entries.
You can reduce the impact of a crowded
CAM
by configuring the
Duplicate MAC Aging Timer
in the
syscfg
command, which is described in Configuring System Information on page 9-
23. This timer allows you to age out Duplicate
MAC CAM
entries from devices that are inac-
tive for the time period you specify.
• Extra search time will be required for each lookup of the same
MAC
address since it is
treated as a separate entry in the
CAM
.
In addition to these performance impacts, you will lose the tracking of legitimate station
moves. No traps will be sent for Duplicate
MAC
addresses that appear in different Groups.