rpf-override

Syntax

rpf-override <SRC-ADDR/SRC-MASK> <RPF-ADDR>

no rpf-override <SRC-ADDR/SRC-MASK> <RPF-ADDR>

Description

The Reverse Path Forward (RPF) override, allows overriding the normal RPF lookup mechanism, and indicates to the router that it may accept multicast traffic on an interface other than the one that the RPF lookup mechanism would normally select. This includes accepting traffic from an invalid source IP address for the subnet or VLAN that is directly connected to the router. Traffic may also be accepted from a valid PIM neighbor that is not on the reverse path towards the source of the received multicast traffic.

The no form of this command removes currently configured RPF entry.

Command context

config-pim6

Parameters

<SRC-ADDR/SRC-MASK>

Specifies the multicast source IPv6 address and mask. Format: X:X::X:X/M

<RPF-ADDR>

Specifies the RPF IPv6 address. Format: X:X::X:X/M

Authority

Administrators

Usage

  • Reverse Path Forward (RPF) checking is a core multicast routing mechanism. The RPF ensures that the multicast traffic received arrives on the expected router interface before further processing. If the RPF check fails for a multicast packet, the packet is discarded. For multicast traffic flow that arrives on the SPT, the expected incoming interface for a given source or group is the interface towards the source address of the traffic (determined by the unicast routing system). For traffic arriving on the RP tree, the expected incoming interface is the interface towards the RP.

  • RPF checking is applied to all multicast traffic and is significant in preventing network loops. Up to eight manual RPF overrides can be specified. The RPF-address indicates one of two distinct RPF candidates:

    1. A valid PIM neighbor address from which forwarded multicast traffic is accepted with a source address of <source-addr/src-mask>.

    2. A local router address on a PIM-enabled interface to which <source-addr/src-mask> is directly connected. If configured, the local router will assume the role of DR for this flow and registers the flow with an RP.

Example

Configuring and removing RPF override: 

switch(config)# router pim6
switch(config-pim6)# rpf-override 2001::01/128 2002::02
switch(config-pim)# no rpf-override 2001::01/128 2002::02