Non-Rpf Traffic Processing - Cisco 7604 Configuration Manual

Chapter 28 Configuring IPv4 Multicast Layer 3 Switching
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With a PFC2, flows matching an output ACL on an outgoing interface are routed in software.
Note
Completely Switched Flows
When all the outgoing 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.
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.
A (*,G) state is created on the PIM-RP or for PIM-dense mode but is not used for forwarding the
Note
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
Figure
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.
The Cisco 7600 series router processes non-RPF traffic in hardware on the PFC by filtering (dropping) or
rate limiting the non-RPF traffic.
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(*,G) flows are partially switched if a DVMRP neighbor is detected on the input interface of a (*,G)
entry.
(*,G) flows are partially switched if the interface and mask entry is not installed for the
RPF-interface of a (*,G) entry and the RPF interface is not a point-to-point interface.
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.
Non-RPF Traffic Overview, page 28-5
Filtering of RPF Failures for Stub Networks, page 28-6
Rate Limiting of RPF Failure Traffic, page 28-6
28-1). In this kind of topology, only the PIM designated router (PIM DR) forwards the data in the
Cisco 7600 Series Router Cisco IOS Software Configuration Guide, Release 12.2SX
Understanding How IPv4 Multicast Layer 3 Switching Works
28-5