Passive Multicast Route Insertion

To prevent unwanted multicast traffic from being sent to the CPU, IPv6 PIM routing and Passive Multicast Route Insertion (PMRI) can be used together to ensure that multicast streams are only forwarded out ports with interested receivers and unwanted traffic is dropped in hardware on Layer 3 routers.

PMRI enables a Layer 3 switch running IPv6 PIM Sparse to create an entry for a multicast route (for example, (S,G)), with no directly attached clients or when connected to another PIM router (transit network).

When a multicast stream has no output interfaces, the Layer 3 switch can drop packets in hardware if the multicast traffic meets the following conditions in IPv6 PIM-SM.

  • The route has no OIF.
  • The directly connected source passes source RPF check and completes data registration with the RP, or the non-directly connected source passes source RPF check.

If the OIF is inserted after the hardware-drop entries are installed, the hardware entries will be updated to include the OIFs.

Note: Disabling hardware-drop does not immediately take away existing hardware-drop entries, they will go through the normal route aging processing when the traffic stops.