Latest supervisor engine - MSFC, PFC

[ajay kondapalli]

What is the latest Sup engine ?  is it sup 720

What is the role of supervisor engine ?

Can any one explain me the exact differnce between , MSFC card, DFC card, and PFC card?

Thanks,

AJAY

[Leo Laohoo]

What is the latest Sup engine ?  is it sup 720

Cisco Catalyst 6500 Series Supervisor Engine 2T

The role of the supervisor engine is to act as the "brain".  Without it, your chassis is a big piece of door jam.

[Richard Michael]

Hi Ajay,

Supervisor in switches takes care of everything its like a brain controlling other line cards and giving out instructions constantly.

Supervisor have following important companents,

1) Processor - RP/SP - MSFC

2) PFC - L2/L3 Fwding engine + TCAM

3) Replication Engine

4) Fabric

Each components has specific duties to perform. When there is a packet lookup  done it programs the hardware TCAM and after which the packets never reach the MSFC it always refers the TCAM - PFC but still all the control packets would be handled by CPU RP/SP. As the name implies replication engine is to replicate handling multicast packets as such.

Now DFC is something that is present in the linecard, It downloads the information from the PFC and the lookup happens locally instead of going all the way to the PFC which is located in the Supervisor. Cool Isn't it?

At present SUP 720 has MSFC3/PFC3 and supports DFC3 LC's.

SUP 2T is the latest and would go with MSFC4/PFC4 and supports DFC4 LC's.

Thanks,

Ricky Micky

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[Jon Marshall]

Ajay

The 6500 is a L3 switch which means it forwards packets at L2 and L3 in hardware (where possible).

There are 2 aspects to a device such as L3 switch being able to forward packets.

1) The control plane. This is responsible primarily for managing the routing tables on the device. On the 6500 the MSFC is responsible for the control plane. It's primary responsibility is to establish peerings with other L3 devices, exchanging routes and building the routing table.

Anything that gets done by the MSFC is done in software ie. it uses the main CPU of the supervisor.

Once the forwarding table has been built it is downloaded to the PFC.

2) The data or forwarding plane. This is responsible for the actual forwarding of the data. On the 6500 the PFC is responsible for for the data plane.  The PFC forwarding is done in hardware not software.

It is very important for a L3 switch to be able to forward as much data in hardware ie. by the PFC. If data has to be sent to the MSFC before being forwarded then that has a negative effect on the performance of the switch.

Even with the PFC a 6500 switch with Centralised forwarding (CFC) means each linecard still has to send a portion of the packet to the supervisor for a forwarding decision. How much of the packet is sent depends on the actual switching mode the whole chassis is in (compact, truncated,  bus).

If you use DFC cards on the linecards then each linecard with a DFC can make a forwarding decision without having to send a portion of the packet to the supervisor. This is done by downloading the forwarding table to each DFC enabled linecard.

Using DFCs dramatically increases the throughput of the whole chassis.

Jon