Q. ip multicast helper: Mcast -> Broadcast -> Mcast

From: sabrina pittarel (sabri_esame@yahoo.com)
Date: Sat Sep 16 2006 - 22:20:23 ART


Hi,
 I'm trying to use the multicast helper feature to convert from multicast to directed broadcast and into multicast again.
 Topology
 
 Mcast transport netw
 Source ---------- R3 ---- .....------ R2 ------- Receiver
 225.25.25.25 1 2 3 4
 
 On R3 interface 1 I convert 225.25.25.25 into directed broadcast for R2 interface 3 subnet (ex 129.1.23.255)
 I have no problem getting this directed brodcast traffic to R2 interface 3.
 On R2 interface 3 I convert broadcast back into 225.25.25.25.
 On R2 interface 4 I'm statically joining the 225.25.25.25 group (for testing purposes).
 PIM Dense mode is enabled on R3 interface 1, R2 interface 4
 
 I cannot make this working if I don't enable pim on R2 interface 3 as well.
 But if I do so, R2 complains because it is receiving multicast traffic on an interface where there are no PIM neighbors and the received traffic is not sourced from the connected network:
 
 *Sep 16 22:16:52.039: %MROUTE-3-NO_PIM_NBR: There is no PIM neighbor on this IDB: Serial1/1 -Process= "PIM Process", ipl= 0, pid= 132
 
 Has anyone been able to make this working without PIM on R2 interface 3?
 
 The configureation is the following:
 
 R3 interface 1:
 -----------------
 
 ip forward-protocol udp 31337
 
 interface Serial1/2
  ip address 129.1.13.3 255.255.255.0
  ip pim dense-mode
  ip multicast helper-map 225.25.25.25 129.1.23.255 100
  encapsulation ppp
  serial restart-delay 0
 
 access-list 100 permit udp 129.1.17.0 0.0.0.255 host 225.25.25.25 eq 31337
 
 R3 interface 2:
 -----------------
 
 interface Serial1/3
  ip address 129.1.23.3 255.255.255.0
  ip directed-broadcast
  encapsulation ppp
 
 
 R2 interface 3:
  -----------------
 
  ip forward-protocol udp 31337
 
 interface Serial1/1
  ip address 129.1.23.2 255.255.255.0
  ip pim dense-mode <<<<< without it it doesn't work...
  ip multicast helper-map broadcast 225.25.25.25 100
  encapsulation ppp
 
 access-list 100 permit udp 129.1.17.0 0.0.0.255 any eq 31337
 
 R2 interface 4:
   -----------------
 
 interface Ethernet0/0
  description "to SW1 e0/2"
  ip address 192.10.1.2 255.255.255.0
  ip pim dense-mode
  ip igmp join-group 225.25.25.25
 
 
 **************************************************
 On R2 Without the "pim" cmd on R3 interface 3:
 **************************************************
 
 "deb ip packet" and "deb ip mpacket" output:
 
 *Sep 17 01:13:28.622: IP: s=129.1.17.7 (Serial1/1), d=255.255.255.255, len 44, rcvd 2
 *Sep 17 01:13:28.622: UDP src=49182, dst=31337
 
 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,
        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
 Outgoing interface flags: H - Hardware switched, A - Assert winner
  Timers: Uptime/Expires
  Interface state: Interface, Next-Hop or VCD, State/Mode
 
 (*, 225.25.25.25), 00:00:03/00:02:56, RP 0.0.0.0, flags: DCL
   Incoming interface: Null, RPF nbr 0.0.0.0
   Outgoing interface list:
     Ethernet0/0, Forward/Dense, 00:00:03/00:00:00
 
 (*, 224.0.1.40), 00:00:03/00:02:56, RP 0.0.0.0, flags: DCL
   Incoming interface: Null, RPF nbr 0.0.0.0
   Outgoing interface list:
     Ethernet0/0, Forward/Dense, 00:00:03/00:00:00
 
 
 *************************************
 On R2 WITH the ip pim dense command
 *************************************
 
 "deb ip packet" and "deb ip mpacket" output:
 
 *Sep 17 01:16:50.618: IP: s=129.1.17.7 (Serial1/1), d=255.255.255.255, len 44, rcvd 2
 *Sep 17 01:16:50.618: UDP src=53508, dst=31337
 *Sep 17 01:16:50.618: IP(0): s=129.1.17.7 (Serial1/1) d=225.25.25.25 (Ethernet0/0) id=0, ttl=252, prot=17, len=44(44), mforward
 
 
 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,
        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
 Outgoing interface flags: H - Hardware switched, A - Assert winner
  Timers: Uptime/Expires
  Interface state: Interface, Next-Hop or VCD, State/Mode
 
 (*, 225.25.25.25), 00:03:23/stopped, RP 0.0.0.0, flags: DCL
   Incoming interface: Null, RPF nbr 0.0.0.0
   Outgoing interface list:
     Ethernet0/0, Forward/Dense, 00:03:23/00:00:00
     Serial1/1, Forward/Dense, 00:01:31/00:00:00
 
 (129.1.17.7, 225.25.25.25), 00:01:33/00:02:58, flags: LT
   Incoming interface: Serial1/1, RPF nbr 0.0.0.0
   Outgoing interface list:
     Ethernet0/0, Forward/Dense, 00:01:33/00:00:00
 
 (*, 224.0.1.40), 00:03:23/00:02:41, RP 0.0.0.0, flags: DCL
   Incoming interface: Null, RPF nbr 0.0.0.0
   Outgoing interface list:
     Ethernet0/0, Forward/Dense, 00:03:23/00:00:00
 
 
 Sabrina



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