8-1. Multilayer Switching

  • Multilayer switching (MLS) performs Layer 3 switching by combining separate routing and switching functions on different switch modules.

  • MLS is supported on the Catalyst 6000 by the MSFC (route processor) and the PFC (Layer 3 switching engine). On the Catalyst 4000 and 5000 platforms, the route processor can be an external router.

  • MLS can perform Layer 3 switching for IP, IP multicast (also known as IP Multicast MLS or MMLS), and IPX traffic.

  • MLS operation consists of these steps:

    - The route processor (RP) routs the first packet in a traffic flow.

    - The switching engine (SE) sets up an MLS cache entry for the flow based on the first packet (a “candidate” packet).

    - When the SE sees the return packet from the RP, the MLS cache ...

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