Administrative Distance, Access Lists, Route Manipulation, and IP Multicast - CCIE Routing and Switching Exam Certification Guide - page 496

Multicast Routing Table
The multicast routing (Mroute) table is shown with the show ip mroute command. It lists the
multicast (*,G) groups for PIM-SM, the RP, and the incoming and outgoing interfaces for the
group. Example 10-19 shows the output for the command.
Example 10-19 show ip mroute Command
router# show ip mroute 237.44.55.100
IP Multicast Routing Table
Flags: D - Dense, S - Sparse, C - Connected, L - Local, P - Pruned
R - RP-bit set, F - Register flag, T - SPT-bit set
Timers: Uptime/Expires
(*, 237.44.55.100), 00:07:40/0:01:43, RP 198.168.75.1, flags: S
Incoming interface: Serial0.2, RPF neighbor 198.168.2.10
Outgoing interface list:
Serial0.3, Forward state, Sparse mode, uptime 00:07:40, expires 0:01:04
Sparse Mode Configuration
As mentioned in the Dense Mode Configuration section, Cisco recommends using the sparse-
dense-mode keyword when running PIM. If the multicast group is running in sparse-mode (that
is, an RP is known), the interface is treated as sparse-mode. Example 10-20 shows a simple
configuration that you can use on all routers running PIM. The ip pim rp-address command
uses the IP address of the RP to tell the router who the RP is.
Example 10-20 Configuration of PIM for Sparse Mode
ip multicast-routing
!
interface ethernet 0
ip address x
ip pim sparse-dense-mode
!
interface ethernet 1
ip address y
ip pim sparse-dense-mode
!
ip pim rp-address address-of-RP
Auto-RP
Another method of configuring the RP for the network is to have the RP announce its services
to the PIM network. This is called Auto-RP . Candidate RPs send their announcements to RP
mapping agents with multicast address 224.0.1.39. RP mapping agents are also configured. In
smaller networks, the RP can be the mapping agent. Configured RP mapping agents listen to
the announcements. The RP mapping agent then selects the RP for a group, based on the highest