Multicast Loopback strange behaviour

Hi GS,

i have configured few routers in series Aluminum-->Platinum -->Brass (RP)
-->TIN -->Iron (Jeff-vol-2 chapter 5,page:505). On Aluminum i have
configured one l0 ip add 172.16.1.1 255.255.255.0 instead of attaching host.

when i ping 236.82.134.23 (iron multicast group joined by loopback). i got
following output...

Aluminum#ping 236.82.134.23 rep 3

Type escape sequence to abort.
Sending 3, 100-byte ICMP Echos to 236.82.134.23, timeout is 2 seconds:

Reply to request 0 from 172.16.2.241, 20 ms
Reply to request 0 from 172.16.2.241, 24 ms
Reply to request 1 from 172.16.2.241, 12 ms
Reply to request 1 from 172.16.2.241, 16 ms
Reply to request 2 from 172.16.2.241, 8 ms
Reply to request 2 from 172.16.2.241, 12 ms

why i am getting duplicate replies?

second sh ip mroute on Aluminum (ping originator) shows

Aluminum#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

(*, 236.82.134.23), 00:02:08/stopped, RP 172.16.224.1, flags: SPF
Incoming interface: Serial1/0, RPF nbr 172.16.2.234
Outgoing interface list: Null

(172.16.1.1, 236.82.134.23), 00:02:08/00:03:21, flags: FT
Incoming interface: Loopback0, RPF nbr 0.0.0.0
Outgoing interface list:
Serial1/0, Forward/Sparse, 00:01:48/00:02:40

(*, 224.0.1.40), 00:02:11/00:02:19, RP 172.16.224.1, flags: SJCL
Incoming interface: Serial1/0, RPF nbr 172.16.2.234
Outgoing interface list:
Loopback0, Forward/Sparse, 00:02:11/00:02:19

all other routers shows

Iron#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

(*, 236.82.134.23), 00:09:04/stopped, RP 172.16.224.1, flags: SJCL
Incoming interface: Serial1/0, RPF nbr 172.16.2.242
Outgoing interface list:
Loopback0, Forward/Sparse, 00:09:04/00:02:46

(172.16.2.233, 236.82.134.23), 00:06:34/00:02:52, flags: LJT
Incoming interface: Serial1/0, RPF nbr 172.16.2.242
Outgoing interface list:
Loopback0, Forward/Sparse, 00:06:34/00:02:46

(172.16.1.1, 236.82.134.23), 00:06:34/00:02:52, flags: LJT
Incoming interface: Serial1/0, RPF nbr 172.16.2.242
Outgoing interface list:
Loopback0, Forward/Sparse, 00:06:34/00:02:46

(*, 224.0.1.40), 00:09:04/00:02:49, RP 172.16.224.1, flags: SJCL
Incoming interface: Serial1/0, RPF nbr 172.16.2.242
Outgoing interface list:
Loopback0, Forward/Sparse, 00:09:04/00:02:49

my second question. why on originator its mapping to loopback 172.16.1.1,
instead of serial interface? and why on all the rest of the routers i can
see two mapping, one for loopback and one for serial?

Thanks in advance for any help.

Best Regards,

Nadeem Rafi

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Received on Tue Dec 01 2009 - 10:26:53 ART