Cisco WS-C4506 - Syst. Catalyst 4500 Switch Manual de usuario descargar pdf (Pagina 40)

BRKARC-3445

Supervisor 6-E Multicast Packet Walk

 1. The packet comes in from the front panel module. Remember the modules on the Cat4K series provides

connectivity between the front panel ports and Packet processor.

 2. Packet Process receives the packet and stores the entire packet into the packet memory. It extract the

header information, packet length, index to the packet memory, plus few other information and that’s the Packet

Lookup Descriptor or PLD. And sends the PLD to the forwarding engine.

 3. The packet goes through L2 lookup and Spanning tree state is checked.

 4a. Input Services, such as input ACL, input policer and input marking are performed on the packet

 4b. Forwarding lookup is done here with TCAM. For multicast packet, it will return the RPF interface, PR ID,

and RET Index.

 4c. Output Service, such as output ACL, output policer and output marking are performed on the packet

 5. Now the replication module will do the RPF check, and it pass, then it consults with the replication table for

the OIL using the RET index.

 6. The lookup from the RET table indicates there are two OIFs (output interfaces), blue interface and gray

interfaces. Replication module will generated two replication request descriptor and send it into the replication

queue. The replication request descriptor has all the information necessary to generated replication lookup

request for every destination of the packet.

 7. The header for blue output interface goes through the forwarding engine pipeline and

 8. following by the header for output interface. As you notice, each copy of the packet goes through the same

pipeline, so you can have different services for the different copy of the packets.

 9. Once the PLD goes through the pipeline, a Packet Transmit Descriptor (or PTD) is generated and send to the

Packet Process. Packet process will reconstruct the packet and send out to the front panel port.

SUP6L-E shares the same architecture

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Cisco WS-C4506 - Syst. Catalyst 4500 Switch Manual de usuario Pagina 40