Configuring CAM Distribution
Page 9-25

Configuring CAM Distribution

CAM (Content Addressable Memory) on switching modules is used to look up the MAC
address of endstations attached to the modules. You can use the camstat command to display
each module’s CAM usage. See Viewing CAM Information on page 9-24 for more information
on the camstat command.
The Omni Switch/Router supports approximately 31.25 K of usable CAM among all the
switching modules in a chassis. (A small amount of CAM memory is reserved by the Omni
Switch/Router for its processing.)
When each switching module in a 9-slot chassis has 1 K of CAM, the 31.25 K limitation is not
reached since only 8 K (assuming 8 switching modules) is used. However, when some
switching modules use 4 K or 8 K of CAM the 31.25 K limitation could be reached quickly.
For example, if all the switching modules in a fully-loaded 9-slot chassis have 4 K CAMs you
would exceed the 31.25 K limit. In this configuration, the Omni Switch/Router would subtract
256 K of available CAM memory from the first switching module to initialize and 512 K of
available CAM memory from the last switching module to initialize. If you need to configure
CAM usage use the camcfg command, which is described below.
♦ Important Note ♦
If you use a configuration file (e.g., mpm.cfg) from an
OmniSwitch on an Omni Switch/Router, any CAM
configuration settings will be ignored.
The camcfg command allows you to individually allocate CAM space to switching modules.
This command configures the maximum entries a switching module may use, freeing up over-
all CAM space in the chassis so that some modules can use more of their on-board CAM.
Follow these two additional rules:
• The CAM memory size for a switching module must be configured to at least one-half of
the total memory available on the switching module. For example, if your switching
module has 2 K of CAM memory, you must allocate at least 1 K of CAM to that switching
module.
• The amount of CAM memory allocated for a switching module must be a whole-number
multiple of 1024 (e.g., 1024, 2048, etc.).
Follow these steps to configure the number of CAM entries used by a switching module:
1. Enter camcfg followed by the slot number for the module that you want to configure. You
can configure the CAM on switching modules only, not on the MPX. For example, to
configure CAM for the module in slot 3, enter
camcfg 3
2. The system displays a prompt asking for the number of CAM entries to use for this
module.
Enter maximum number of CAM entries for slot 3 (1024):
Enter the number of CAM entries to use for this module. The current value is listed in
parentheses. The value you enter must be equal to or less than the total number of entries
available on board this module. For example, you could not configure 2048 entries for a
switching module with only 1K of CAM.