From: HP-France,ex2 ("SANCHEZ-MONGE,ANTONIO)
Date: Wed Oct 08 2003 - 04:18:01 GMT-3
Thanks a lot Brian for detailed answer. The workaround proposed by Rolando
(setting r2 as RP) works as well (disregarding pim nbma-mode on or off).
Maybe RPF rules are applied in a slightly different way by the RP than
non-RP routers (I don't know).
Cheers,
Antonio.
-----Original Message-----
From: Brian McGahan [mailto:bmcgahan@internetworkexpert.com]
Sent: miircoles, 08 de octubre de 2003 4:02
To: 'SANCHEZ-MONGE,ANTONIO (HP-France,ex2)'; 'Alvarez, Rolando [NCSUS]';
ccielab@groupstudy.com
Subject: RE: Multicast in NBMA
This does not relate to PIM running in NBMA mode. PIM NBMA mode is
used to cut down on the amount of replicated unicast traffic sent over a
non-broadcast circuit, and to avoid mistakenly removing a group from a
multipoint non-broadcast interface when an explicit leave message is
received, and there are still clients who want to receive traffic for said
group.
The problem you are seeing is due to the fact that your outgoing
interface and your incoming interface cannot be the same. This principle is
similar to how IP split-horizon works for distance vector routing protocols.
A router will not forward a multicast packet out the same interface it is
received in.
The workaround in this case would be to run point-to-point IP
subnets, or to tunnel the multicast traffic from R3 to R4 through a GRE
tunnel.
HTH,
Brian McGahan, CCIE #8593
bmcgahan@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
Toll Free: 877-224-8987
Direct: 708-362-1418 (Outside the US and Canada)
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
Of
> SANCHEZ-MONGE,ANTONIO (HP-France,ex2)
> Sent: Tuesday, October 07, 2003 11:29 AM
> To: 'Alvarez, Rolando [NCSUS]'; 'ccielab@groupstudy.com'
> Subject: RE: Multicast in NBMA
>
> Hi Rolando, Ozgur,
>
> That's it, using sparse mode and setting r2 as RP fixes the issue.
>
> Thanks a lot to ALL.
>
> Cheers,
> Antonio.
>
> -----Original Message-----
> From: Alvarez, Rolando [NCSUS] [mailto:RAlvare5@NCSUS.JNJ.COM]
> Sent: martes, 07 de octubre de 2003 17:55
> To: 'SANCHEZ-MONGE,ANTONIO (HP-France,ex2)'
> Subject: RE: Multicast in NBMA
>
>
>
> Antonio,
>
> I am not a multicast expert by any means, but I will try to give you
my
> opinion. For this topology, I would try using Auto-RP so that the
> multicast runs on sparse-mode. I think that you may be running into
> the Reverse Path
> Forwarding that dense-mode uses. Since the packet came in on s0/0.30,
it
> will not forward that packet out that same interface. Try making r2
the
> rp
> and ma for this group, and your issue may be resolved. Let me know if
> that helps.
>
> Thanks,
> Rolando
> -----Original Message-----
> From: SANCHEZ-MONGE,ANTONIO (HP-France,ex2)
> [mailto:antonio.sanchez-monge@hp.com
<mailto:antonio.sanchez-monge@hp.com>
> ]
>
> Sent: Tuesday, October 07, 2003 8:32 AM
> To: 'ccielab@groupstudy.com'
> Subject: Multicast in NBMA
>
>
> Hi All,
>
> Nice to meet you. I am beginning to prepare CCIE lab.
>
> Could you please help me with this problem?
>
> My topology: Frame-relay multipoint
> r2 192.168.30.2(lo0 = 192.168.2.2)
> / / \
> / / \
> / / \
> / / \
> (r4)(r3) (r5)
> |________|
>
>
> OSPF is running everywhere, every router can ping the others'
loopbacks.
> Also PIM Sparse-Dense is running everywhere.
> The frame-relay maps are all configured for broadcast.
>
> The Ethernet interface of r3 (192.168.20.3) and r2 loopback
(192.168.2.2)
> are multicast group 225.6.7.8 receivers.
>
> When the multicast sender is r4, only r2 replies, whereas if it is r2
the
> sender, r3 replies too.
>
> I think this has to do with the multipoint architecture, but I cannot
see
> how to get a reply from r3 r4 (or how to get r2 forwarding the
multicast
> packet originated by r4 to r3). Any clues?
>
>
> r2#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 Outgoing
> interface flags: H - Hardware switched
> Timers: Uptime/Expires
> Interface state: Interface, Next-Hop or VCD, State/Mode
>
> (*, 224.0.1.40), 00:44:09/00:00:00, RP 0.0.0.0, flags: DCL
> Incoming interface: Null, RPF nbr 0.0.0.0
> Outgoing interface list:
> Serial0/0.30, Forward/Sparse-Dense, 00:44:09/00:00:00
>
> (*, 225.6.7.8), 00:15:22/00:00:00, RP 0.0.0.0, flags: DCL
> Incoming interface: Null, RPF nbr 0.0.0.0
> Outgoing interface list:
> Loopback0, Forward/Sparse-Dense, 00:07:56/00:00:00
> Serial0/0.30, Forward/Sparse-Dense, 00:15:22/00:00:00
>
> (192.168.2.2, 225.6.7.8), 00:00:07/00:02:52, flags: CLT
> Incoming interface: Loopback0, RPF nbr 0.0.0.0
> Outgoing interface list:
> Serial0/0.30, Forward/Sparse-Dense, 00:00:10/00:00:00
>
> (192.168.30.4, 225.6.7.8), 00:02:57/00:00:03, flags: CLT
> Incoming interface: Serial0/0.30, RPF nbr 192.168.30.4
> Outgoing interface list:
> Loopback0, Forward/Sparse-Dense, 00:02:57/00:00:00
>
>
> r2#i
> Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B -
BGP
> D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
> N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
> E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
> i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS
> level-2
>
> ia - IS-IS inter area, * - candidate default, U - per-user
static
> route
> o - ODR, P - periodic downloaded static route
>
> Gateway of last resort is not set
>
> 192.168.30.0/24 is variably subnetted, 4 subnets, 2 masks
> O 192.168.30.4/32 [110/64] via 192.168.30.4, 00:30:40,
Serial0/0.30
> O 192.168.30.5/32 [110/64] via 192.168.30.5, 00:30:40,
Serial0/0.30
> O 192.168.30.3/32 [110/64] via 192.168.30.3, 00:30:40,
Serial0/0.30
> C 192.168.30.0/28 is directly connected, Serial0/0.30
> 192.168.4.0/32 is subnetted, 1 subnets
> O 192.168.4.4 [110/65] via 192.168.30.4, 00:30:40, Serial0/0.30
> 192.168.2.0/32 is subnetted, 1 subnets
> C 192.168.2.2 is directly connected, Loopback0
> 192.168.3.0/32 is subnetted, 1 subnets
> O 192.168.3.3 [110/65] via 192.168.30.3, 00:30:41, Serial0/0.30
>
>
> Thanks & Cheers,
> Antonio.
>
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>
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