Cisco Systems EA6500 Manual De Usuario
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Catalyst 6500 Series Switch Cisco IOS Software Configuration Guide—Release 12.1 E
78-14099-04
Chapter 18 Configuring IP Multicast Layer 3 Switching
Understanding How IP Multicast Layer 3 Switching Works
Partially Switched Flows with PFC2
In PFC2 systems, (*,G) flows will be partially switched on the last-hop leaf router if the shared-tree to
shortest-path-tree (SPT) threshold is not equal to infinity. This allows the flow to transition from SPT.
shortest-path-tree (SPT) threshold is not equal to infinity. This allows the flow to transition from SPT.
Note
With a PFC2, flows matching an output ACL on an outgoing interface are routed in software.
Completely Switched Flows
When all the outgoing Layer 3 interfaces for a given flow are Layer 3 switched, and none of the above
situations apply to the flow, that flow is considered completely switched. When a completely switched
flow is created, the PFC prevents multicast traffic bridged on the source VLAN for that flow from
reaching the MSFC interface in that VLAN, freeing the MSFC of the forwarding and replication load for
that flow.
situations apply to the flow, that flow is considered completely switched. When a completely switched
flow is created, the PFC prevents multicast traffic bridged on the source VLAN for that flow from
reaching the MSFC interface in that VLAN, freeing the MSFC of the forwarding and replication load for
that flow.
One consequence of a completely switched flow is that multicast statistics on a per-packet basis for that
flow cannot be recorded. Therefore, the PFC periodically sends multicast packet and byte count statistics
for all completely switched flows to the MSFC. The MSFC updates the corresponding multicast routing
table entry and resets the expiration timer for that multicast route.
flow cannot be recorded. Therefore, the PFC periodically sends multicast packet and byte count statistics
for all completely switched flows to the MSFC. The MSFC updates the corresponding multicast routing
table entry and resets the expiration timer for that multicast route.
Note
A (*,G) state is created on the PIM-RP or for PIM-dense mode but is not used for forwarding the flows,
and Layer 3 switching entries are not created for these flows.
and Layer 3 switching entries are not created for these flows.
Non-RPF Traffic Processing
These sections describe non-RPF traffic processing:
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Non-RPF Traffic Overview
In a redundant configuration where multiple routers connect to the same LAN segment, only one router
forwards the multicast traffic from the source to the receivers on the outgoing interfaces (see
forwards the multicast traffic from the source to the receivers on the outgoing interfaces (see
). In this kind of topology, only the PIM designated router (PIM DR) forwards the data in the
common VLAN, but the non-PIM DR receives the forwarded multicast traffic. The redundant router
(non-PIM DR) must drop this traffic because it has arrived on the wrong interface and fails the RPF
check. Traffic that fails the RPF check is called non-RPF traffic.
(non-PIM DR) must drop this traffic because it has arrived on the wrong interface and fails the RPF
check. Traffic that fails the RPF check is called non-RPF traffic.
The Catalyst 6500 series switch processes non-RPF traffic in hardware on the PFC by filtering (dropping)
or rate limiting the non-RPF traffic.
or rate limiting the non-RPF traffic.