Re: Multicast Loopback strange behaviour

Nadeem,

The router is probably sending multiple pings, one for each interface
enabled with PIM. You should be able to do "debug ip icmp" to verify this.

On Tue, Dec 1, 2009 at 3:26 AM, <nrafia_at_gmail.com> wrote:

> 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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Bryan Bartik
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