The functionality and differentiate between MSFC & PFC

[parazhang]

Can someone explain the functionality of the following and differentiate between them - MSFC, PFC?
When I purchase a Supervisor Engine to make our enterprise L3 Switching,should I must buy both of MSFC and PFC? Or I can select one of them?
I have found some Supervisor Engines have both of them, some have only PFC,and others have only MSFC.Oh,my god!I really want to know the relation and differ between them,thx!

 

[ADB100]

For a Catalyst 6500 Supervisor to run as a layer-3 device (router) then you MUST have an MSFC - whether it is an MSFC1, MSFC2 or MSFC3. The MSFC is the actual router, the PFC is the packet forwarder and re-writer.

Simply put the MSFC makes the initial forwarding decision of a packet, the PFC cache's this information and forwards any subsequent packets, it obviously rewrites the layer-2 headers when routing packets between VLAN's (or interfaces). The MSFC updates the forwarding table in the PFC. The MSFC also run's your routing protocols etc.

The PFC can also rewrite the Layer-3 headers in packets to change the TOS Field (IP Precedence/DSCP) so is used for QoS. It can do this with or without the MSFC. What it can't do without the MSFC is route packets between VLAN's.

For Supervisor2 the PFC2 is not an option it is integrated, the MSFC2 is optional though. For the older Supervisor1 the PFC1 was an option as well as the MSFC or MSFC2. For the Sup720 I think the PFC3 and MSFC3 are no longer options and are integrated to the Supervisor.

You have 2 options with Software as well: If your Supervisor does not have an MSFC then you must run CatOS. If you have a MSFC then you have the option of running 'Hybrid' where the Supervisor runs CatOS and handles the Layer-2 functions and the MSFC runs IOS and handles the Layer-3 functions. Or you can run Native (Integrated) IOS where a single image runs and controls the Layer-2 & Layer-3 functions (like the 3550, 3560 & 3750 switches)

Hope this helps

Andy

 

[parazhang]

Thx andy!
If I purchase a catalyst 6509 with supervisor,and there is a PFC card in it only,then can this supervisor make Layer3 routing and forwarding?

 

[ADB100]

No - the you MUST have an MSFC installed on the Supervisor to perform any routing.

Andy

 

[parazhang]

Then what can the PFC card do on the supervisor without MSFC? Thx!

 

[ADB100]

Without the MSFC the PFC can be used to restrict traffic using security ACL's or to re-classify traffic for QoS purposes.

Andy