From: Chuck Ryan (chryan) (chryan@cisco.com)
Date: Wed Oct 08 2008 - 19:25:09 ART
Looks like I'll have to send this email in 2 parts due to size
restrictions of the list....I'll send the configs seperately...
Ok I made more progress on this....
if you stick a router inbetween your C-RP and the mapping agent
router....then it does not work. The reason for this is because the
router in the middle receives the RP announce message, but he can't
flood it out all of his PIM-enabled interfaces because he's configured
for pim sparse-mode only. So he receives the RP announce message, and
his oilist for 224.0.1.39 is null, so he drops the packet. He also sends
a prune message to the C-RP telling him to quit sending him the traffic
because he has no interested receivers for 224.0.1.39. See the debug
below (debug ip mpacket detail).....
R3#
*Oct 8 21:45:43.987: IP(0): MAC sa=aabb.cc00.6b00 (Ethernet0/0)
*Oct 8 21:45:43.987: IP(0): IP tos=0xC0, len=48, id=99, ttl=15, prot=17
*Oct 8 21:45:43.987: IP(0): s=11.11.11.11 (Ethernet0/0) d=224.0.1.39
id=99, ttl=15, prot=17, len=62(48), mroute olist null
*Oct 8 21:45:44.091: PIM(0): Insert (11.11.11.11,224.0.1.39) prune in
nbr 10.1.37.7's queue
*Oct 8 21:45:44.095: PIM(0): Building Join/Prune packet for nbr
10.1.37.7
*Oct 8 21:45:44.095: PIM(0): Adding v2 (11.11.11.11/32, 224.0.1.39)
Prune
*Oct 8 21:45:44.095: PIM(0): Send v2 join/prune to 10.1.37.7
(Ethernet0/0)
R3#
If the C-RP and the mapping agent router are directly connected, then
everything works fine. If you seperate them, then it does not work, and
that is the correct behavior. Here is the simple topology:
BB1 e0/0 ------ e0/0 R3 s1/1 -------- s1/1 R1
BB1 is the C-RP
R3 is a PIM-enabled router
R1 is the MA (mapping agent) router
In the simple 3 router topology, this will not work beyond the 3rd
router (R1), the non-rp that is directly connected to the MA. That
router will receive the RP mapping info from the MA because he's
directly connected to it. Once he receives it, he will not forward it
(flood it) out any of his interfaces without the use of "ip pim
sparse-dense" configured at the interface level or "ip pim autorp
listener" configured globally.
If this is totally wrong, someone please correct me. I've been playing
with this all day though, and this is what I have experienced.
Thanks,
Chuck
Blogs and organic groups at http://www.ccie.net
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