Multicast mroute issue

[mark_tegg]

Hi

Please could someone explain the below output from the command issued.

The mutlicast source is as below 10.120.50.69.

Two things in question.

     1.) Why is the *,232.0.10.38 forwarding?

     2.) What is it forwarding?

1# sh ip mroute 232.0.10.38

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
       V - RD & Vector, v - Vector
Outgoing interface flags: H - Hardware switched, A - Assert winner
Timers: Uptime/Expires
Interface state: Interface, Next-Hop or VCD, State/Mode

(*, 232.0.10.38), 2d05h/00:02:47, RP 10.120.0.224, flags: S
  Incoming interface: Null, RPF nbr 0.0.0.0
  Outgoing interface list:
    Vlan906, Forward/Sparse-Dense, 00:01:29/00:02:47

(10.120.50.69, 232.0.10.38), 00:01:29/00:01:30, flags: M
  Incoming interface: Vlan722, RPF nbr 10.120.46.66
  Outgoing interface list:
    Vlan906, Forward/Sparse-Dense, 00:01:29/00:02:47

Thanks,

Mark

[Mohamed Sobair · Accepted solution]

Hi Mark,

The Output indicates that a Multicast host joined the shared tree for the Group 232.x.x.x, the *.232 means a shared tree is cretaed, and the RP information is known which is 10.120.0.224.

The Shared tree is Rooted at the RP FIRST, and then it switch to a source based tree if not configured otherwise.

and RPF neighbor of 0.0.0.0 , indicates that this router is an RP for the multicast group.

HTH

Mohamed