Multicast - AutoRP RPListener

Overview

The Cisco AutoRP feature relies on PIM dense mode to communicate between mapping agent and candidate RPs. This can create problems if dense mode is enabled on large networks. The command ip pim autorp-listener attempts to address this by allowing dense mode only for the 224.0.1.39 and 224.0.1.40 groups which allow sparse-mode hosts to communicate with their RPs and limits dense mode across the multicast domain.

Concepts tested

• AutoRP with PIM sparse mode only
• Limiting dense mode in an AutoRP multicast network
• Configuring AutoRP

Topology

Lab Tasks

• Configure PIM Sparse mode on all paths between the source and receiver routers
• Using Cisco's proprietary RP feature configure R2 and R3 as RPs
• Configure R4 as a RP mapping agent
• Ensure that the RPs and the mapping agent can communicate PIM AutoRP messages without enabling dense mode explicitly on the routers
• Verify your configuration by making sure all hosts can hear AutoRP messages.

GNS3 configuration file, requires IOS v15 for the 7200 router: Link


Solution

Receiver:

Receiver(config)#ip multicast-routing
Receiver(config)#int g0/0

Receiver(config-if)#ip pim sparse-mode
Receiver(config)#int g0/0
Receiver(config-if)#exit
Receiver(config)#ip pim autorp listener

R2:

R2(config)#ip multicast-routing
R2(config)#int g0/0
R2(config-if)#ip pim sparse-mode
R2(config-if)#exit
R2(config)#int s2/0
R2(config-if)#ip pim sparse-mode
R2(config-if)#exit
R2(config)#int loopback 0
R2(config-if)#ip pim sparse-mode
R2(config-if)#exit
R2(config)#ip pim send-rp-announce loopback 0 scope 10
R2(config)#ip pim autorp listener

R3:

R3(config)#ip multicast-routing
R3(config)#int g0/0
R3(config-if)#ip pim sparse-mode
R3(config-if)#exit
R3(config)#int g1/0
R3(config-if)#ip pim sparse-mode
R3(config-if)#exit
R3(config)#int loopback 0
R3(config-if)#ip pim sparse-mode
R3(config-if)#exit
R3(config)#ip pim send-rp-announce loopback 0 scope 10
R3(config)#ip pim autorp listener

R4:

R4(config)#ip multicast-routing
R4(config)#int g0/0
R4(config-if)#ip pim sparse-mode
R4(config-if)#exit
R4(config)#int g1/0
R4(config-if)#ip pim sparse-mode
R4(config-if)#exit
R4(config)#int g2/0
R4(config-if)#ip pim sparse-mode
R4(config-if)#exit

R4(config)#int s3/0

R4(config-if)#ip pim sparse-mode
R4(config-if)#exit
R4(config)#int loopback 0
R4(config-if)#ip pim sparse-mode
R4(config-if)#exit
R4(config)#ip pim send-rp-discovery loopback 0 scopre 10
R4(config)#ip pim send-rp-discovery loopback 0 scope 10
R4(config)#ip pim autorp listener

Souce:

Source(config)#ip multicast-routing
Source(config)#int g0/0
Source(config-if)#ip pim sparse-mode
Source(config-if)#exit

Verification

R4#sh ip pim rp map
PIM Group-to-RP Mappings
This system is an RP-mapping agent (Loopback0)

Group(s) 224.0.0.0/4
  RP 3.3.3.3 (?), v2v1
    Info source: 3.3.3.3 (?), elected via Auto-RP
         Uptime: 00:04:47, expires: 00:02:11
  RP 2.2.2.2 (?), v2v1
    Info source: 2.2.2.2 (?), via Auto-RP
         Uptime: 00:04:41, expires: 00:02:16

R4#sh ip pim interface

Address          Interface                Ver/   Nbr    Query  DR     DR
                                          Mode   Count  Intvl  Prior
0.0.0.0          GigabitEthernet0/0       v2/S   0      30     1      0.0.0.0
120.0.34.4       GigabitEthernet1/0       v2/S   1      30     1      120.0.34.4
120.0.24.4       Serial3/0                v2/S   1      30     1      0.0.0.0
4.4.4.4          Loopback0                v2/S   0      30     1      4.4.4.4
120.0.45.4       GigabitEthernet2/0       v2/S   1      30     1      120.0.45.5

Source#sh ip pim rp mapping
PIM Group-to-RP Mappings

Group(s) 224.0.0.0/4
  RP 3.3.3.3 (?), v2v1
    Info source: 4.4.4.4 (?), elected via Auto-RP
         Uptime: 00:00:14, expires: 00:02:44

Source#sh ip mroute
IP Multicast Routing Table
Flags: D - Dense, S - Sparse, B - Bidir Group, s - SSM Group, C - Connected,
       L - Local, P - Pruned, R - RP-bit set, F - Register flag,
       T - SPT-bit set, J - Join SPT, M - MSDP created entry, E - Extranet,
       X - Proxy Join Timer Running, A - Candidate for MSDP Advertisement,
       U - URD, I - Received Source Specific Host Report,
       Z - Multicast Tunnel, z - MDT-data group sender,
       Y - Joined MDT-data group, y - Sending to MDT-data group,
       V - RD & Vector, v - Vector
Outgoing interface flags: H - Hardware switched, A - Assert winner
 Timers: Uptime/Expires
 Interface state: Interface, Next-Hop or VCD, State/Mode

(*, 224.0.1.39), 00:00:53/stopped, RP 0.0.0.0, flags: DC
  Incoming interface: Null, RPF nbr 0.0.0.0
  Outgoing interface list:
    GigabitEthernet0/0, Forward/Sparse, 00:00:53/00:00:00

(2.2.2.2, 224.0.1.39), 00:00:20/00:02:39, flags: PTX
  Incoming interface: GigabitEthernet0/0, RPF nbr 120.0.45.4
  Outgoing interface list: Null

(3.3.3.3, 224.0.1.39), 00:00:26/00:02:33, flags: PTX
  Incoming interface: GigabitEthernet0/0, RPF nbr 120.0.45.4
  Outgoing interface list: Null

(*, 224.0.1.40), 00:03:06/stopped, RP 0.0.0.0, flags: DCL
  Incoming interface: Null, RPF nbr 0.0.0.0
  Outgoing interface list:
    GigabitEthernet0/0, Forward/Sparse, 00:03:06/00:00:00

(4.4.4.4, 224.0.1.40), 00:00:27/00:02:32, flags: PLTX
  Incoming interface: GigabitEthernet0/0, RPF nbr 120.0.45.4
  Outgoing interface list: Null