Saturday, May 18, 2013


Supervisor 1A with PFC-1 and MSFC-1/MSFC-2

Let us continue right from where we had left in the last post.

The last Supervisor 1A option and only L3 switching option for the Catalyst 6000/6500 using the Supervisor 1A is the Supervisor 1A module with PFC-1 and MSFC-1 or MSFC-2 installed.

Why can't you still use MSFC-1 ???
Well MSFC-1 is now end of sale i.e. Cisco no longer manufactures it.
So you can only purchase the MSFC-2 if you want to add Layer 3 switching capabilities to existing Supervisor 1A configurations.

Differences between MSFC-1 and MSFC-2.

1. Processor
The MSFC-1 has an R5000 200-MHz processor.
The MSFC-2 has an R7000 300-MHz processor.

2. Memory
MSFC-1 supports up to 128 MB memory.
MSFC-2 supports up to 512 MB memory.

3.  Speed
MSFC-1 can route packets at 170K pps (packets per second).
MSFC-2 can route packets at 650K pps.

The Layer 3 switching performance in hardware is still 15 Mpps, regardless of the MSFC used.

Fig 31.2.2

 In Fig 31.2.2, the addition of the MSFC allows for the L3 engine to L3 switch inter-VLAN traffic. All other features of the PFC, such as QoS classification and ACL filtering are also supported. The PFC-1 and MSFC-1/MSFC-2 use multilayer switching (MLS) to perform L3 switching; this means that a flow cache exists on the PFC which is used to L3 switch packet flows through the switch. The first packet within a flow must always be routed by the MSFC, which references the routing table to determine the next hop information for a packet. Once the MSFC has made a routing decision and forwarded the frame back to the L3 engine, the L3 engine reads the routed frame information and writes this information into the flow cache. Subsequent packets received and that match flow cache entries can now be L3 switched by the L3 engine, rather than the MSFC.
Limitation of the MLS L3 switching mechanism is the initial route lookup performed in software by the MSFC. The first packet in an IP flow must be passed to the MSFC route processor for routing. In an environment that has many connections being established at the same time, this can cause performance problems for the MSFC. This problem in particular applies to service provider environments, which typically must handle conditions where many short term connections (e.g., downloading a web page might open several HTTP connections that are terminated immediately once the page is downloaded) are being established at once.

The Supervisor 1 with PFC-1 and MSFC can L3 switch packets at 15 Mpps.

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