RE: mroute

From: Alt, Ryan (ryan.alt@berbee.com)
Date: Fri Sep 14 2007 - 18:46:23 ART


The first solution that comes to mind is a GRE tunnel, but I'm not sure exactly why it doesn't work. That's an interesting problem...

________________________________

From: nobody@groupstudy.com on behalf of robert.steeneken@getronics.com
Sent: Fri 9/14/2007 3:23 PM
To: ccielab@groupstudy.com
Subject: mroute

A question about mroute on a lan. I have the following situation.
             R1
             |
             R2 (RP)
             |
             R4
            / \
           / \
          R5 R6
        __|______|__
             |
            R7

On R5 is multicast not enabled.
In the routing table on R7 is R5 the next hop to reach to R4 R2 and R1
So on R7 the rpf check fails, when I add the next mroute

 *, 224.2.2.2), 00:13:55/00:02:56, RP 140.40.2.2, flags: SCL
  Incoming interface: FastEthernet0.56, RPF nbr 140.40.56.5
  Outgoing interface list:
    Loopback0, Forward/Sparse, 00:13:55/00:02:56

R7(config)#ip mroute 140.40.2.2 255.255.255.255 140.40.56.6

(*, 224.2.2.2), 00:00:02/00:02:57, RP 140.40.2.2, flags: SCL
  Incoming interface: FastEthernet0.56, RPF nbr 140.40.56.5, Mroute
  Outgoing interface list:
    Loopback0, Forward/Sparse, 00:00:02/00:02:57

A ping to 224.2.2.2 (both loopbacks on R6 and R7 have a igmp join) only shows a result for R6 and not R7

But when i divide the lan between R5 R6 R7 in two seperated vlans and I change the mroute

ip mroute 140.40.2.2 255.255.255.255 140.40.76.6

(*, 224.2.2.2), 00:01:04/00:02:59, RP 140.40.2.2, flags: SCL
  Incoming interface: FastEthernet0.76, RPF nbr 140.40.76.6, Mroute
  Outgoing interface list:
    Loopback0, Forward/Sparse, 00:01:04/00:02:25

Now the RPF check don't fails and a ping to 224.2.2.2 works.

What did I wrong in the first situation? Or how could I have fixed the RPF with a mroute.

Robert.



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