From: Joe Chang (changjoe@earthlink.net)
Date: Wed Jun 02 2004 - 14:57:31 GMT-3
Because R2 sought to join the SPT of the multicast, and determined the best
path to it's source is 10.1.1.1 it's best path is through s1/0.
Recall that when a sparse mode peer becomes aware of a multicast group it
will first join the shared tree. Hence the initial state of your mroute
table.
----- Original Message -----
From: "Sergio Jimenez Arguedas" <sejimenez@its.co.cr>
To: <ccielab@groupstudy.com>
Sent: Tuesday, June 01, 2004 8:22 PM
Subject: RPF Check in IP Multicast!!!
> Hi Group,
>
> I have the following scenario:
>
>
>
>
> 10.1.1.1/24--Loop1--R1_s0/0______________________s1/0___R2--FE0/0--Group
> 226.7.6.5
>
> R1 and R2 have a EIGRP enable, and also a GRE Tunnel:
>
> R2#sh ip eigrp neighbors
> IP-EIGRP neighbors for process 100
> H Address Interface Hold Uptime SRTT RTO Q Seq
Type
> (sec) (ms) Cnt Num
> 1 138.1.11.156 Tu0 14 02:40:47 36 5000 0 10
> 0 138.1.11.156 Se1/0 138 02:51:53 30 1140 0 11
>
> RP:R1
> MA:R1
>
> When I make a ping from R1 to the Group 226.7.6.5 with the source address
> 10.1.1.1....I got the following in R2:
>
> +++++++Before the ping:
>
> R2#sh ip mroute 226.7.6.5
> 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
> Outgoing interface flags: H - Hardware switched
> Timers: Uptime/Expires
>
> Interface state: Interface, Next-Hop or VCD, State/Mode
>
> (*, 226.7.6.5), 00:00:11/00:00:00, RP 172.16.6.6, flags: SJCL
> Incoming interface: Tunnel0, RPF nbr 138.1.11.156, Mroute
> Outgoing interface list:
> Ethernet0/0, Forward/Sparse-Dense, 00:00:11/00:02:48
>
>
> +++++++In the moment of the ping: (debug ip mpacket 226.7.6.5)
>
> 03:48:19: IP: s=10.1.1.1 (Tunnel0) d=226.7.6.5 len 100, RPF lookup failed
for
> source
> 03:48:19: IP: s=10.1.1.1 (Tunnel0) d=226.7.6.5 (Ethernet0/0) len 100,
> mforward
>
> ++++The ip mroute table:
>
> R2#sh ip mroute 226.7.6.5
> 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
> Outgoing interface flags: H - Hardware switched
> Timers: Uptime/Expires
>
> Interface state: Interface, Next-Hop or VCD, State/Mode
>
> (*, 226.7.6.5), 00:03:30/00:00:00, RP 172.16.6.6, flags: SJCL
> Incoming interface: Tunnel0, RPF nbr 138.1.11.156, Mroute
> Outgoing interface list:
> Ethernet0/0, Forward/Sparse-Dense, 00:03:30/00:02:29
> (10.1.1.1, 226.7.6.5), 00:00:37/00:02:22, flags: CLJ
> Incoming interface: Null, RPF nbr 138.1.11.156
> Outgoing interface list:
> Ethernet0/0, Forward/Sparse-Dense, 00:00:37/00:02:29
>
>
> ++++THE QUESTION IS THE FOLLOWING:
>
> In R2 I don4t have the ip mroute 10.1.1.0 255.255.255.0 Tunnel 0. So I
> understand that the RPF fail,
>
> 03:48:19: IP: s=10.1.1.1 (Tunnel0) d=226.7.6.5 len 100, RPF lookup failed
for
> source
>
> After the debug notification shows mforward:
>
> 03:48:19: IP: s=10.1.1.1 (Tunnel0) d=226.7.6.5 (Ethernet0/0) len 100,
> mforward
>
> I really don4t understand WHY the ping got response in R1,
>
> R1#ping
> Protocol [ip]:
> Target IP address: 226.7.6.5
> Repeat count [1]:
> Datagram size [100]:
> Timeout in seconds [2]:
> Extended commands [n]: yes
> Interface [All]: loop 1
> Time to live [255]:
> Source address: 10.1.1.1
> Type of service [0]:
> Set DF bit in IP header? [no]:
> Validate reply data? [no]:
> Data pattern [0xABCD]:
> Loose, Strict, Record, Timestamp, Verbose[none]:
> Sweep range of sizes [n]:
> Type escape sequence to abort.
> Sending 1, 100-byte ICMP Echos to 226.7.6.5, timeout is 2 seconds:
> Packet sent with a source address of 10.1.1.1
>
> Reply to request 0 from 138.1.11.130, 36 ms
>
>
> ......If in theory the RPF don4t pass!!!
>
>
> Look the sh ip route 10.1.1.0 255.255.255.0 in R2:
>
> R2#sh ip route 10.1.1.1 255.255.255.0
> Routing entry for 10.1.1.0/24
> Known via "eigrp 100", distance 90, metric 20640000, type internal
> Redistributing via eigrp 100
> Last update from 138.1.11.156 on Serial1/0, 01:52:44 ago
> Routing Descriptor Blocks:
> * 138.1.11.156, from 138.1.11.156, 01:52:44 ago, via Serial1/0
> Route metric is 20640000, traffic share count is 1
> Total delay is 25000 microseconds, minimum bandwidth is 128 Kbit
> Reliability 255/255, minimum MTU 1500 bytes
> Loading 1/255, Hops 1
>
>
>
> Thanks in Advance,,,,
>
>
>
>
> Sergio Jiminez Arguedas...
>
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