From: Scott Strobeck (scott@strobeck.net)
Date: Sun Jul 27 2008 - 13:33:02 ART
Hi David,
The issue I saw is that the hub (multipoint) configured for sparse mode
won't, by default, forward mcast back out the interface. You would
either need to create a tunnel between R2 & R3, or enable "ip pim
nbma-mode" on the multipoint on R1. If you do a "debug ip pim bsr" on
R2, you'll see that it never receives the BSR announcement. What you
will see, however, is that when R2 goes to build its RP-Candidate
announcement, it fails because it doesn't have the address of the BSR to
send the message to.. . . I was intrigued, so I dynamipped this. . ..
R2#debug ip pim bsr
PIM-BSR debugging is on
R2#
*Mar 1 18:11:41.399: PIM-BSR(0): Build v2 Candidate-RP advertisement for 10.0.2.2 priority 0, holdtime 150
*Mar 1 18:11:41.403: PIM-BSR(0): Candidate RP's group prefix 232.0.0.0/5
*Mar 1 18:11:41.403: PIM-BSR(0): no bootstrap router addressR2#
Enabling 'ip pim nbma-mode' on R1 causes the bsr message to make it to
R2. .. Here's R2 debug afterward. . . Voila, now your RP-mappings are
there...
R2#
*Mar 1 18:15:04.207: PIM-BSR(0): triggered v2 Candidate-RP advertisements to 10.0.3.3
*Mar 1 18:15:04.231: PIM-BSR(0): 10.0.3.3 bootstrap forwarded on Loopback0
*Mar 1 18:15:04.231: PIM-BSR(0): 10.0.3.3 bootstrap forwarded on Serial1/0
*Mar 1 18:15:04.251: PIM-BSR(0): bootstrap (10.0.3.3) on non-RPF path Loopback0 or from non-RPF neighbor 10.0.0.1 discarded
R2#
R2#
R2#
*Mar 1 18:15:41.571: PIM-BSR(0): Build v2 Candidate-RP advertisement for 10.0.2.2 priority 0, holdtime 150
*Mar 1 18:15:41.575: PIM-BSR(0): Candidate RP's group prefix 232.0.0.0/5
*Mar 1 18:15:41.575: PIM-BSR(0): Send Candidate RP Advertisement to 10.0.3.3
*Mar 1 18:15:41.855: PIM-BSR(0): 10.0.3.3 bootstrap forwarded on Loopback0
*Mar 1 18:15:41.859: PIM-BSR(0): 10.0.3.3 bootstrap forwarded on Serial1/0
*Mar 1 18:15:41.875: PIM-BSR(0): bootstrap (10.0.3.3) on non-RPF path Loopback0 or from non-RPF neighbor 10.0.0.1 discarded
R2#
R2#
R2#sh ip pi rp ma
PIM Group-to-RP Mappings
This system is a candidate RP (v2)
Group(s) 224.0.0.0/5
RP 10.0.1.1 (?), v2
Info source: 10.0.3.3 (?), via bootstrap, priority 0, holdtime 150
Uptime: 00:00:47, expires: 00:02:17
Group(s) 232.0.0.0/5
RP 10.0.2.2 (?), v2
Info source: 10.0.3.3 (?), via bootstrap, priority 0, holdtime 150
Uptime: 00:00:09, expires: 00:02:17
R2#
So, NO, the BSR candidate doesn't have to be the hub. In a live
environment, however, you'd want to choose the bsr and rp's as centrally
located routers with a good deal of BW. Also, you didn't forget your
bsr-candidate config, as suggested below.
Now, here's an interesting twist. This set-up is using EIGRP.
Everything works fine. The first time I did this, however, I used OSPF
and ran into a problem. Here's the debug on R2 when initially running
ospf on the network:
R2#
*Mar 1 18:42:06.775: PIM-BSR(0): bootstrap (10.0.3.3) on non-RPF path Serial1/0 or from non-RPF neighbor 10.0.0.3 discarded
R2#
This brings up an interesting difference between OSPF and EIGRP in a
hub-and-spoke environment. This is the kind of obscure thing they might
throw into the lab. In the routing table, EIGRP will show the
advertising router as the next hop, but OSPF will list the originating
neighbor on the segment. Here's the output below before and after
replacing OSPF with EIGRP:
R2#sh ip route eigrp
10.0.0.0/24 is subnetted, 4 subnets
D 10.0.3.0 [90/2809856] via 10.0.0.1, 02:52:16, Serial1/0
D 10.0.1.0 [90/2297856] via 10.0.0.1, 02:54:59, Serial1/0
R2#
R2#sh ip route ospf
10.0.0.0/24 is subnetted, 4 subnets
O 10.0.3.0 [110/65] via 10.0.0.3, 00:00:04, Serial1/0
O 10.0.1.0 [110/65] via 10.0.0.1, 00:00:04, Serial1/0
I'm not sure exactly why the RPF check fails (anybody care to go into
that?), but through experimentation, I found that it didn't like the
next-hop address being 10.0.0.3 on s1/0. I found two ways to remedy
this. The first is to change the ospf network types on the serials to
point-to-point and point-to-multipoint (don't forget your hello
intervals). (By default, these network types are non-broadcast, so I
originally just added neighbor statements on R1.) This change fixes the
next-hop in the routing table:
R2#sh ip route ospf
10.0.0.0/8 is variably subnetted, 5 subnets, 2 masks
O 10.0.3.0/24 [110/129] via 10.0.0.1, 00:05:01, Serial1/0
O 10.0.1.0/24 [110/65] via 10.0.0.1, 00:05:01, Serial1/0
O 10.0.0.1/32 [110/64] via 10.0.0.1, 00:05:01, Serial1/0
The second way to fix this is to add an mroute for 10.0.3.3 with a
next-hop of 10.0.0.1.
I can see this being a very good situation to throw at you in the real
lab. How to get it all working depends on the constraints they give
you. Just remember that when something doesn't work, DEBUG!!!
Good luck,
Scott
shiran guez wrote:
Hi David
you are missing some config,
ip pim bsr-candidate *type number* *hash-mask-length* [*priority*]
for the bootstrap router (R1 in your case).
also in hub and spoke you want only the hub to be the RP and not one of the
spokes!
also you do not need to set ip pim sparse-dense mode a ip pim sparse is
enough.
you can read this http://www.netcraftsmen.net/welcher/papers/multicast04.html or http://cciep3.blogspot.com/2007/10/ccie-pim-auto-rp.html although this is
explaining AutoRP it will give you some ground for Multicast.
On 7/26/08, David Lonnie <david.lonnie@gmail.com> wrote:
Hi,experts:
I have a question about bsr.
R1,R2,R3 are in frame-relay cloud,and R1 is hub,R2 and R3 are spokes.
R1:
interface s0/0
ip pim sparse-dense-mode
interface l0
ip pim sparse-dense-mode
access-list 30 permit 224.0.0.0 7.255.255.255
ip pim rp-candidate Loopback0 group-list 30
R2:
interface s0/0
ip pim sparse-dense-mode
interface l0
ip pim sparse-dense-mode
access-list 30 permit 232.0.0.0 7.255.255.255
ip pim rp-candidate Loopback0 group-list 30
R3:
interface s0/0
ip pim sparse-dense-mode
interface l0
ip pim sparse-dense-mode
ip pim bsr-candidate lo0
When i verified on R3:
R3#sh ip pi rp mapping
PIM Group-to-RP Mappings
This system is the Bootstrap Router (v2)
Group(s) 224.0.0.0/5
RP 11.11.1.1 (?), v2
Info source: 11.11.123.1 (?), via bootstrap, priority 0, holdtime 210
Uptime: 00:00:15, expires: 00:03:08
My question is that,why i can's see R2 is RP for 232.0.0.0/5?
Can somebody explain for me?
This is my debug information.
R3#debug ip pim bsr
*Jul 25 09:44:58.762: PIM-BSR(0): RP 11.11.1.1, 1 Group Prefixes,
Priority
0, H
oldtime 210
R5#
*Jul 25 09:45:03.462: PIM-BSR(0): RP-set for 224.0.0.0/5
*Jul 25 09:45:03.462: PIM-BSR(0): RP(1) 11.11.1.1, holdtime 210 sec
priority 0
*Jul 25 09:45:03.466: PIM-BSR(0): Bootstrap message for 11.11.3.3originated
R2#debug ip pim bsr
*Mar 9 17:42:25.970: PIM-BSR(0): Build v2 Candidate-RP advertisement for
11.11.
2.2 priority 0, holdtime 210
*Mar 9 17:42:25.970: PIM-BSR(0): Candidate RP's group prefix 232.0.0.0/5
*Mar 9 17:42:25.970: PIM-BSR(0): no bootstrap router address
R2#
*Mar 9 17:43:26.022: PIM-BSR(0): Build v2 Candidate-RP advertisement for
11.11.
2.2 priority 0, holdtime 210
*Mar 9 17:43:26.022: PIM-BSR(0): Candidate RP's group prefix 232.0.0.0/5
*Mar 9 17:43:26.022: PIM-BSR(0): no bootstrap router address
David
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