Cisco Distributed Forwarding Card for 65xx, 6816 Modules used with SUP2 Guida Specifiche
Catalyst 6500 Series Switches PFC, DFC, and CFC FAQ
Introduction
This document addresses the frequently asked questions on the Policy Feature Card (PFC), Distributed Forwarding
Card (DFC), and Centralized Forwarding Card (CFC) of the Cisco Catalyst 6500 Series switches.
Q. What happens when you mix different versions of the PFC3x and DFC3x?
A. The PFC3 is the ASIC-based forwarding engine daughtercard for the Sup720; the DFC3 is the ASIC-based
forwarding engine daughtercard for various fabric-enabled linecards (CEF256, CEF720). The PFC3/DFC3 generation is
built upon a forwarding architecture known as EARL7. Within this generation, there are three different versions – 'A',
'B', and 'BXL' – that are all based on the same fundamental technologies but that each have incremental functionality.
'A' is the standard offering; 'B' is the intermediate option, and 'BXL' is the high-end option.
Since these versions are all within the same generation, it is possible that these versions can coexist within the same
chassis with similar operation, but there are functional differences between them. A system with a mixture of
forwarding engines only operates with the capabilities of the least-capable forwarding engine in the chassis. We
cannot allow each forwarding engine to operate independently in its own mode. The BXL to run in BXL mode, the B to
run in B mode, etc. within the same chassis is not allowed. This is because forwarding tables cannot be synchronized
if we allow each PFC3/DFC3 to have different capabilities within the same system. For example, if the FIB table grows
to 500K entries, the system is not able to provide consistent operation if it downloaded that 500K FIB table to the
PFC3BXL/DFC3BXL modules but not to the PFC3A/DFC3A and PFC3B/DFC3B modules. The same situation applies for
an ACL configuration that requires more than 512 ACL labels. It is for these reasons that a mixture of PFC3/DFC3
versions must operate in a least-common-denominator mode so that tables can remain synchronized, and features
can be applied consistently across interfaces.
This document addresses the frequently asked questions on the Policy Feature Card (PFC), Distributed Forwarding
Card (DFC), and Centralized Forwarding Card (CFC) of the Cisco Catalyst 6500 Series switches.
Q. What happens when you mix different versions of the PFC3x and DFC3x?
A. The PFC3 is the ASIC-based forwarding engine daughtercard for the Sup720; the DFC3 is the ASIC-based
forwarding engine daughtercard for various fabric-enabled linecards (CEF256, CEF720). The PFC3/DFC3 generation is
built upon a forwarding architecture known as EARL7. Within this generation, there are three different versions – 'A',
'B', and 'BXL' – that are all based on the same fundamental technologies but that each have incremental functionality.
'A' is the standard offering; 'B' is the intermediate option, and 'BXL' is the high-end option.
Since these versions are all within the same generation, it is possible that these versions can coexist within the same
chassis with similar operation, but there are functional differences between them. A system with a mixture of
forwarding engines only operates with the capabilities of the least-capable forwarding engine in the chassis. We
cannot allow each forwarding engine to operate independently in its own mode. The BXL to run in BXL mode, the B to
run in B mode, etc. within the same chassis is not allowed. This is because forwarding tables cannot be synchronized
if we allow each PFC3/DFC3 to have different capabilities within the same system. For example, if the FIB table grows
to 500K entries, the system is not able to provide consistent operation if it downloaded that 500K FIB table to the
PFC3BXL/DFC3BXL modules but not to the PFC3A/DFC3A and PFC3B/DFC3B modules. The same situation applies for
an ACL configuration that requires more than 512 ACL labels. It is for these reasons that a mixture of PFC3/DFC3
versions must operate in a least-common-denominator mode so that tables can remain synchronized, and features
can be applied consistently across interfaces.
PFC Card
DFC Card
Resultant
Mode
Mode
Comments
PFC3A
DFC3A
PFC3A mode
No restrictions
DFC3B
The PFC3A restricts DFC3B functionality
DFC3BXL
The PFC3A restricts DFC3BXL functionality
DFC3C
The PFC3A restricts DFC3C functionality
DFC3CXL
The PFC3A restricts DFC3CXL functionality
PFC3B
DFC3A
PFC3A mode
PFC3B functionality is restricted by the DFC3A
DFC3B
PFC3B mode
No restrictions
DFC3BXL
The PFC3B restricts DFC3BXL functionality
DFC3C
The PFC3B restricts DFC3C functionality
DFC3CXL
The PFC3B restricts DFC3CXL functionality
PFC3BXL
DFC3A
PFC3A mode
PFC3BXL functionality is restricted by the DFC3A
DFC3B
PFC3B mode
PFC3BXL functionality is restricted by the DFC3B
DFC3C
PFC3B mode
Each restricts the functionality of the other: the PFC3BXL functions
as a PFC3B, and the DFC3C functions as a DFC3B (PFC3B mode).
as a PFC3B, and the DFC3C functions as a DFC3B (PFC3B mode).
DFC3BXL
PFC3BXL mode
No restrictions
DFC3CXL
The PFC3BXL restricts DFC3CXL functionality
Mixing DFCs and PFCs also impacts on-line insertion and removal (OIR). If a line card with DFC3B is inserted into a
switch with SUP720-3BXL, the line card does not power up. In order to use DFC3A-equipped switching modules with
a PFC3BXL or PFC3B, the DFC3A-equipped switching modules must be installed at boot up. In order to use DFC3B-
equipped switching modules with a PFC3BXL, the DFC3B-equipped switching modules must be installed at boot up.
The system also displays a similar error message: OIR-6-DOWNGRADE_EARL: Module [dec] DFC installed is not
identical to system PFC and will perform at current system operating mode. This is an example of the error message: