Hi James, The register message is unicast so it it routed direct to R6 address 215.0.0.6. Where this will break is when the routers try to switch over to the shortest path tree. Try doing a ping with a repeat of 5. You'll probably find that only the first ping gets a reply and the rest timeout.
cheers, Ben. From: James Roc <[email protected]<mailto:[email protected]>> Date: Monday, 23 April 2012 12:32 PM To: "[email protected]<mailto:[email protected]>" <[email protected]<mailto:[email protected]>> Subject: [OSL | CCIE_RS] PIM sparse-mode tree built through router with no RP configuration Hi Everyone, Im playing around with multicast and found an interesting issue where I have the following setup: r6 -- r1 --- r9 --- r5 I'm running pim sparse mode on all interfaces and ospf for unicast connectivity. I have R6 setup as the RP with a static command on R6, R1 and R5 'ip pim rp-address 215.0.0.6'. R9 has *no* RP configuration. I join a group on R6s loopback and ping from R5. The ping is successful. This is confusing to me as the way I understand PIM, R5 would send a group 'Register' to the RP via R9. R9 would receive this but having no knowledge of the RP, would simply drop the packet and respond back with a Register Stop. However, somehow the group register is making its way to the RP, SPT is built and pings flow. How/why is R9 forwarding the PIM register message if it does not know where the RP is? Thanks James PIM Debugs below show the tree being built. r5 ---- R5(config)#do ping 232.8.8.8 Type escape sequence to abort. Sending 1, 100-byte ICMP Echos to 232.8.8.8, timeout is 2 seconds: *Mar 1 01:20:28.727: PIM(0): Check RP 215.0.0.6 into the (*, 232.8.8.8) entry *Mar 1 01:20:28.727: PIM(0): Send v2 Register to 215.0.0.6 for 215.0.0.5, group 232.8.8.8 *Mar 1 01:20:28.727: IP(0): s=215.0.0.5 (Loopback0) d=232.8.8.8 id=187, ttl=254, prot=1, len=100(100), mroute olist null *Mar 1 01:20:28.751: PIM(0): Received v2 Join/Prune on FastEthernet0/1.59 from 215.5.9.9, to us *Mar 1 01:20:28.751: PIM(0): Join-list: (215.0.0.5/32, 232.8.8.8), S-bit set *Mar 1 01:20:28.755: PIM(0): Add FastEthernet0/1.59/215.5.9.9 to (215.0.0.5, 232.8.8.8), Forward state, by PIM SG Join. R5(config)#do un all All possible debugging has been turned off R5(config)#do ping 232.8.8.8 Type escape sequence to abort. Sending 1, 100-byte ICMP Echos to 232.8.8.8, timeout is 2 seconds: Reply to request 0 from 215.1.6.6, 28 ms R5(config)# r9 --- R9(config-subif)# *Mar 1 01:20:26.907: PIM(0): Received v2 Join/Prune on FastEthernet0/1.19 from 215.1.9.1, to us *Mar 1 01:20:26.907: PIM(0): Join-list: (215.0.0.5/32, 232.8.8.8), S-bit set *Mar 1 01:20:26.907: PIM(0): Add FastEthernet0/1.19/215.1.9.1 to (215.0.0.5, 232.8.8.8), Forward state, by PIM SG Join *Mar 1 01:20:26.907: PIM(0): Insert (215.0.0.5,232.8.8.8) join in nbr 215.5.9.5's queue *Mar 1 01:20:26.907: PIM(0): Building Join/Prune packet for nbr 215.5.9.5 *Mar 1 01:20:26.907: PIM(0): Adding v2 (215.0.0.5/32, 232.8.8.8), S-bit Join *Mar 1 01:20:26.907: PIM(0): Send v2 join/prune to 215.5.9.5 (FastEthernet0/1.59) R9(config-subif)# R9(config-subif)#do sh ip mroute (*, 232.8.8.8), 00:01:40/stopped, RP 0.0.0.0, flags: SP Incoming interface: Null, RPF nbr 0.0.0.0 Outgoing interface list: Null (215.0.0.5, 232.8.8.8), 00:01:40/00:02:33, flags: T Incoming interface: FastEthernet0/1.59, RPF nbr 215.5.9.5 Outgoing interface list: FastEthernet0/1.19, Forward/Sparse, 00:01:40/00:02:48 R9(config-subif)# r1 --- R1(config)# *Mar 1 01:20:27.907: PIM(0): Received v2 Join/Prune on FastEthernet0/0.16 from 215.1.6.6, to us *Mar 1 01:20:27.907: PIM(0): Join-list: (215.0.0.5/32, 232.8.8.8), S-bit set *Mar 1 01:20:27.907: PIM(0): Check RP 215.0.0.6 into the (*, 232.8.8.8) entry *Mar 1 01:20:27.907: PIM(0): Add FastEthernet0/0.16/215.1.6.6 to (215.0.0.5, 232.8.8.8), Forward state, by PIM SG Join *Mar 1 01:20:27.907: PIM(0): Insert (215.0.0.5,232.8.8.8) join in nbr 215.1.9.9's queue *Mar 1 01:20:27.907: PIM(0): Building Join/Prune packet for nbr 215.1.9.9 *Mar 1 01:20:27.907: PIM(0): Adding v2 (215.0.0.5/32, 232.8.8.8), S-bit Join R1(config)# *Mar 1 01:20:27.907: PIM(0): Send v2 join/prune to 215.1.9.9 (FastEthernet0/0.19) R1(config)# r6 --- R6(config)# *Mar 1 01:20:28.439: PIM(0): Received v2 Register on FastEthernet0/0.16 from 215.5.9.5 *Mar 1 01:20:28.439: for 215.0.0.5, group 232.8.8.8 *Mar 1 01:20:28.447: PIM(0): Insert (215.0.0.5,232.8.8.8) join in nbr 215.1.6.1's queue *Mar 1 01:20:28.447: PIM(0): Forward decapsulated data packet for 232.8.8.8 on Loopback0 *Mar 1 01:20:28.447: PIM(0): Building Join/Prune packet for nbr 215.1.6.1 *Mar 1 01:20:28.447: PIM(0): Adding v2 (215.0.0.5/32, 232.8.8.8), S-bit Join *Mar 1 01:20:28.447: PIM(0): Send v2 join/prune to 215.1.6.1 (FastEthernet0/0.16) R6(config)#do un all All possible debugging has been turned off R6(config)# _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com Are you a CCNP or CCIE and looking for a job? Check out www.PlatinumPlacement.com http://onlinestudylist.com/mailman/listinfo/ccie_rs _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com Are you a CCNP or CCIE and looking for a job? Check out www.PlatinumPlacement.com http://onlinestudylist.com/mailman/listinfo/ccie_rs
