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Chapter 13
Configuring CEF for PFC2 and PFC3A
Follow these guidelines when specifying the maximum number of routes that can be programmed in the
FIB TCAM:
Routes that exceed the specified number of routes are not installed in the hardware. Packets that take
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those routes are switched by the MSFC. The routes argument is a unit of 1,000 entries. Setting the
routes argument to 0 returns the system to a system-determined default value.
When no protocols are set, an initial default value is assigned for each protocol. When at least one
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protocol is set, the default value for other unassigned protocols might change as the system tries to
assign the remaining space to the unassigned protocols.
This command has the following characteristics:
Changing the setting takes effect only after rebooting the active supervisor engine. The change does
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not take effect after a switchover.
The setting on the standby supervisor engine is synchronized with the active supervisor engine. If
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the standby supervisor engine is inserted, both the bootup setting and new setting, if existing, on the
active supervisor engine are synchronized with the standby supervisor engine. The standby
supervisor engine uses the bootup setting to configure the FIB TCAM. The standby supervisor
engine might need to be reset if its original bootup setting is different from the bootup setting of the
active supervisor engine. An informational message (FIB_MAXROUTES_RESET) is printed on the
active supervisor engine console if this situation occurs.
To maximize the TCAM utilization, we recommend that you set the maximum routes for IP unicast
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as a multiple of 16,000 and set the maximum routes for IP multicast as a multiple of 8,000. The
internal allocation scheme uses 16,000 as the allocation unit for unicast and 8,000 as the allocation
unit for multicast. For example, if IP unicast is set to 1,000, 16,000 entries are reserved, but only
1,000 is allowed.
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When the maximum routes are exceeded or the allocated TCAM space for a protocol is full, a system
message (FIB_ALLOC_TCAM_FULL) displays. Because of the internal software allocation
scheme, the allocated TCAM space might be full before the maximum routes are exceeded.
The sum of the number of maximum routes for all protocols cannot exceed 256,000.
Note
If the routes values for all protocols are set to 0, the bootup default is used. When you set the routes value
Note
for one protocol to a non-zero value, the default value for the other protocol changes to the remaining
size.
If the maximum number of routes is not set for an MLS protocol, a system-determined default value is
Note
shown. The default value for a protocol might not be fixed, as the system tries to assign the remaining
space to the unassigned protocols. If the maximum-routes configuration is changed after bootup, the
show mls cef maximum-routes command displays two kinds of information: one for the current
(bootup) configuration and the other for the new configuration that takes effect after reboot.
OL-8978-04
Catalyst 6500 Series Switch Software Configuration Guide—Release 8.7
Configuring CEF for PFC2/PFC3A on the Switch
13-17
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