S/M, 224/4 - Cisco Catalyst 4500 Series Software Configuration Manual

Chapter 38 Configuring IP Multicast
When PIM-SM routing is in use, the MFIB route might include an interface as in this example:
Note
PimTunnel [1.2.3.4].
it is a virtual interface that the MFIB subsystem creates to indicate that packets are being tunnelled to
the specified destination address. A PimTunnel interface cannot be displayed with the normal show
interface command.

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.
Multicast HA
Starting with Release IOS XE 3.4.0SG and IOS 15.1(2)SG, the Catalyst 4500/4900/4900X Series
switches support multicast HA, which ensures uninterrupted multicast traffic flow in the event of a
supervisor engine failure. MFIB states are synced to the standby supervisor engine prior to a switchover,
ensuring NSF availability with a fast convergence upon switchover during a supervisor engine failure.
Multicast HA (SSO / NSF / ISSU) is supported for the PIM Sparse, Dense, Bidir, and SSM Modes; and
at Layer 2 for IGMP and MLD Snooping.
For details on Multicast HA, please refer to the following URLs:
http://www.cisco.com/en/US/docs/ios-xml/ios/ipmulti_resil/configuration/xe-3s/imc_high_availability.
html
Configuring IP Multicast Routing
The following sections describe IP multicast routing configuration tasks:
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Default Configuration in IP Multicast Routing, page 38-14
Enabling IP Multicast Routing, page 38-14
Enabling PIM on an Interface, page 38-15
Enabling Bidirectional Mode, page 38-16
Enabling PIM-SSM Mapping, page 38-17
Configuring a Rendezvous Point, page 38-17
Configuring a Single Static RP, page 38-21
Load Splitting of IP Multicast Traffic, page 38-22
Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS 15.2(5)Ex
Configuring IP Multicast Routing
38-13