# Enabling and Disabling RPF Checks

By default, the router accepts multicast packets for each Source, Group (S,G) pair on an incoming interface (IIF), which satisfies the RPF check (RPF-IIF). When the router performs RPF checks, only the interface that first accepts traffic for an (S,G) pair accepts subsequent traffic for that pair. If traffic stops arriving on that interface and starts arriving on another interface, the router does not accept or forward the traffic.

Some network configurations require the router to accept traffic on any interface. To do so, you can disable the RPF check on a specified set of (S,G) pairs by issuing the ip multicast-routing disable-rpf-check command.

When you disable RPF checks, the router accepts multicast packets for (S,G) pairs on any incoming interface. When the router has added the new route to its multicast routing table, it then accepts multicast packets for these pairs on any interface in the virtual router and forwards them accordingly. Multicast routes established before you issue this command are not affected.

ip multicast-routing disable-rpf-check

- Use to disable RPF checks for specified (S,G) pairs.
- Specify a standard IP access list that defines the (S,G) pairs.
- Example
  host1(config)#ip multicast-routing disable-rpf-check boston-list
- Use the no version to restore the default, in which the router performs RPF checks for all (S,G) pairs.
- See ip multicast-routing disable-rpf-check.