From: Gustavo Novais (gustavo.novais@novabase.pt)
Date: Sun Dec 11 2005 - 12:43:34 GMT-3
Hi Chris,
I agree with what you say, but I was sourcing my pings from a
fastethernet interface on R4, meaning vlan 4 (not tunnel0), that is why
I thought I should have the mroute on.
One other thing is, if you notice the mroute table I've sent I have
always the FT flags, meaning that the source is always registering to
R1? That is strange because the RP to that group is R4, not R1?
Could you explain? (As you can see my multicast knowledge is pretty
scrambled up. :-( I'll start reading Beau's book.)
Gustavo Novais
________________________________
From: Chris Lewis [mailto:chrlewiscsco@gmail.com]
Sent: domingo, 11 de Dezembro de 2005 15:20
To: Gustavo Novais
Cc: ccielab@groupstudy.com
Subject: Re: Multicast over GRE tunnel question. Help to understand a
concept
If you configured IP addresses on the tunnel interface you would not
need an mroute. The thinking is that if say each end is addressed as
follows:
10.1.1.1/24 on R1 and 10.1.1.4/24,
The 10.1.1.0 subnet is a connected network, so when the ping from R4
comes over the tunnel, it is sourced from 10.1.1.4, arriving on the
tunnel interface, which coincides with the interface the router will use
to reply, so no RPF check fails.
Chris
On 12/10/05, Gustavo Novais <gustavo.novais@novabase.pt> wrote:
Hello,
I'm doing lab 11 of IEWB3 the multicast section.
We have a hub and spoke frame-relay network, being R3 the Hub and R1 and
R4
the spokes.
R3 is using its main interface. PIM sparse-mode everywhere and R3 is the
BSR.
R4 is the C-RP for the group we will test 228.34.28.100.
We cannot use ip pim nbma-mode.
The question is that a PC in vlan 7 (behind sw1, attached to R1) cannot
receive the feed from a source located on vlan 4 (behind R4).
Configure the network to solve this problem and so that SW1 (hanging on
R1
Fa0/0) responds to ICMP echo requests from vlan 4.
I solved this by configuring a tunnel between R1 and R4 loopbacks,
running PIM
sparse on it. I'm not running any routing protocol (besides PIM) on the
tunnel. So, the tunnel network is not known anywhere else on the
network, not
even by R3 (the hub of the FR network).
I was expecting to have to configure a static mroute on R1 pointing to
the
source network through the tunnel.
My doubt is, why did the ping from R4 vlan 4 to the group 228.34.28.100,
on
which SW1 participated through an igmp join-group, worked without the
static
mroute?
The show ip mroute on R1 simply states that the RPF neighbor Is 0.0.0.0,
but I
think it should be R4's tunnel interface.
Can anybody explain?
I send show ip mroute on R1
Rack1R1#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
(*, 224.0.1.40), 00:30:27/00:02:42, RP 0.0.0.0, flags: DPL
Incoming interface: Null, RPF nbr 0.0.0.0
Outgoing interface list: Null
(*, 228.34.28.100), 00:30:26/stopped, RP 150.1.4.4, flags: SF
Incoming interface: Serial0/0.134, RPF nbr 187.1.134.3
Outgoing interface list:
FastEthernet0/0, Forward/Sparse, 00:29:36/00:02:32
( 187.1.14.4 <http://187.1.14.4> , 228.34.28.100), 00:00:10/00:03:23,
flags: FT
Incoming interface: Tunnel0, RPF nbr 0.0.0.0
Outgoing interface list:
FastEthernet0/0, Forward/Sparse, 00:00:10/00:03:28
Rack1R1#sh ip mroute static
Rack1R1#
Thank you
Gustavo Novais
Network Engineer AAN - All Area Networks
Cisco CCNP, CQS-Wireless.
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