This lab is set-up for Auto-RP, for this to work we must specify an RP-Candidate “ip pim send-rp-announce [interface] scope [0-255] and RP-Mapping “ip pim send-rp-discovery [interface] scope [0-255] interval [seconds]”

“ip pim auto rp listener” This command needs to be on any other routers participating in PIM, what this does is allow the dense-mode flooding of RP-Announce (224.0.1.39) and RP-Discovery (224.0.1.40) messages thus allowing the RP to be elected on a Sparse-Mode network.

Auto-RP topology

Attached are the config’s for each router (Router Configs). As I’m using GNS3 I had to enter commands “no ip route-cache” and “no ip mroute-cache” on each PIM interface. Also add “no ip cef”. You won’t need this for physical routers.

Now lets confirm configurations with some well-known commands.

Run ” debug ip pim auto-rp” from the mapping agent this shows us the RP-Announce received from R3 and also shows the mapping agent R2 sending RP-Discovery messages out both PIM enabled interfaces.

*Mar 1 00:06:28.719: Auto-RP(0): Received RP-announce packet of length 48, from 15.15.15.3, RP_cnt 1, ht 181
*Mar 1 00:06:28.723: Auto-RP(0): Update (224.0.0.0/4, RP:15.15.15.3), PIMv2 v1
*Mar 1 00:07:21.475: Auto-RP(0): Send RP-discovery packet of length 48 on FastEthernet0/1 (1 RP entries)
*Mar 1 00:07:21.475: Auto-RP(0): Send RP-discovery packet of length 48 on FastEthernet0/0(*) (1 RP entries)

From R1 run the command “sh ip pim rp mapping” this shows that the RP was elected via Auto-RP

Group(s) 224.0.0.0/4
 RP 15.15.15.3 (?), v2v1
 Info source: 56.56.56.2 (?), elected via Auto-RP
 Uptime: 00:09:37, expires: 00:02:17

Confirm the auto-rp multicast address’ are in the mroute table with the command “show ip mroute” this shows the source tree entries for the mapping-agent (224.0.1.40) and the RP-Announce (224.0.1.39)

(15.15.15.3, 224.0.1.39), 00:00:28/00:02:31, flags: PT
Incoming interface: FastEthernet0/0, RPF nbr 56.56.56.2
Outgoing interface list: Null

(56.56.56.2, 224.0.1.40), 00:12:39/00:02:14, flags: PLT
Incoming interface: FastEthernet0/0, RPF nbr 56.56.56.2
Outgoing interface list: Null

Generate some traffic from R1 multicast source 232.4.4.4, R4 has already sent the IGMP join message to the RP for the group, so will have the IGMP connected group and begin to build the initial shared tree then eventually the source tree to R1.

 (*, 232.4.4.4), 03:23:51/stopped, RP 15.15.15.3, OIF count: 1, flags: SJC
(56.56.56.1, 232.4.4.4), 00:00:04/00:02:55, OIF count: 1, flags:

This confirms our multicast setup is working correctly.

RH

 

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