One of my friends recently mentioned his plans to upgrade some Cisco Catalyst 6500 linecards with DFCs (distributed forwarding cards), and was wondering which DFC to use. I told him the short answer was ‘It depends on the sup.’ Here are some of my notes on the subject.
The DFCs are field-upgradeable Ethernet module daughter cards that provide distributed forwarding capabilities to some Catalyst 6500 linecards.
When upgrading, your best option is to pick a DFC that matches the capabilities of the PFC (policy feature card) of the existing supervisor and the capabilities of the other DFC modules. You also have to match the DFC model with the linecard type you are upgrading. For example, the F6K modules work with the 65xx linecards, the F6700 modules work with the 67xx linecards.
The following chart outlines the options depending on sup is in the chassis:
| Supervisor | Matching DFC | 61xx Linecard |
6608 Linecard |
6516 6816 Linecard |
67xx Linecard |
| Sup 720-3A | WS-F6700-DFC3A | — | — | — | yes |
| WS-F6K-DFC3A | — | — | yes | — | |
| Sup 720-3B | WS-F6700-DFC3B | — | — | — | yes |
| WS-F6K-DFC3B | — | — | yes | — | |
| Sup 720-3BXL | WS-F6700-DFC3BXL | — | — | — | yes |
| WS-F6K-DFC3BXL | — | — | yes | — | |
| Sup 720-10G | WS-F6700-DFC3C | — | — | — | yes, * |
| Sup 720-10GXL | WS-F6700-DFC3CXL | — | — | — | yes, ** |
Notes:
* DFC3C is standard on the WS-X6708-10G-3C and the WS-X6716-10G-3C Ethernet modules
** DFC3CXL is standard on the WS-X6708-10G-3CXL and the WS-X6716-10G-3CXL Ethernet modules
If you have a range of DFCs or PFCs in the chassis, the system forces operation at level of the least-capable forwarding engine, whether the PFC or DFC, because the forwarding engines are all synchronized. For example, a PFC3C operating in 3B mode offers only those features supported by a PFC3B. You can verify the PFC operating mode with the show platform hardware pfc mode command.
The capabilities of the forwarding engines vary depending on the PFC/DFC. Some examples: the DFC3A, DFC3B, and DFC3C all support 256,000 routes and 128,000 NetFlow entries while the DFC3BXL and DFC3CXL support 1,000,000 IPv4 routes and 256000 NetFlow entries.VSS mode is currently only supported in PFC3C or PFC3CXL, so is not supported with any DFC3A, DFC3B, or DFC3BXL in the system. The DFC3B and DFB3XL support 64,000 MAC entries, while the DFC3C and DFC3XL support 96,000 MAC entries. The DFC3A does not supports MPLS, but all other DFCs do.
The 61xx and 6608 linecards are central forwarding only, and do not support DFCs. The system will run the CFC (centralized forwarding card) at a maximum of 15 Mpps of forwarding when classic-mode line cards are present, and lowest common level PFC/DFC for sups and line cards that support distributed forwarding.
— cwr
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If you would like some additional details, the following references should be helpful:
http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/hardware/Module_Installation/Mod_Install_Guide/0adtrcrd.html#wp1007726
http://www.cisco.com/en/US/products/hw/switches/ps708/products_qanda_item09186a00809a7673.shtml
http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps708/prod_bulletin0900aecd8017a5db.html