33-13
Software Configuration Guide—Release 15.0(2)SG
OL-23818-01
Chapter 33 Configuring IP Multicast Configuring IP Multicast Routing

S/M, 224/4

An (S/M, 224/4) entry is created in the MFIB for every multicast-enabled interface. This entry ensures
that all packets sent by directly connected neighbors can be register-encapsulated to the PIM-SM RP.
Typically, only a small number of packets are forwarded using the (S/M,224/4) route, until the (S,G)
route is established by PIM-SM.
For example, on an interface with IP address 10.0.0.1 and netmask 255.0.0.0, a route is created matching
all IP multicast packets in which the source address is anything in the class A network 10. This route can
be written in conventional subnet/masklength notation as (10/8,224/4). If an interface has multiple
assigned IP addresses, then one route is created for each such IP address.

Restrictions on Using Bidirectional PIM

Restrictions include the following:
IPv4 Bidirectional (Bidir) PIM is supported on Catalyst 4900M, Catalyst 4948E, Supervisor Engine
6-E, and Supervisor Engine 6L-E. IPv6 Bidir PIM is not supported.
The Catalyst 4500 series switch allows you to forward Bidir PIM traffic in hardware up to a
maximum of seven RPs. If you configure more than seven Bidir RPs, only the first seven RPs can
forward traffic in hardware. The traffic directed to the remaining RPs is forwarded in software.
Configuring IP Multicast Routing
The following sections describe IP multicast routing configuration tasks:
Default Configuration in IP Multicast Routing, page 33-13
Enabling IP Multicast Routing, page 33-14
Enabling PIM on an Interface, page 33-14
Enabling Bidirectional Mode, page 33-16
Enabling PIM-SSM Mapping, page 33-17
Configuring a Rendezvous Point, page 33-17
Configuring a Single Static RP, page 33-20
Load Splitting of IP Multicast Traffic, page 33-22
For more detailed information on IP multicast routing, such as Auto-RP, PIM Version 2, and IP multicast
static routes, refer to the Cisco IOS IP and IP Routing Configuration Guide, Cisco IOS Release 12.3.

Default Configuration in IP Multicast Routing

Table 33-1 shows the IP multicast default configuration.