Re: Multicast - AUTO-RP with SPARSE mode - how does the

From: Shivjit Patil (shivjitp@yahoo.com)
Date: Tue May 16 2006 - 16:36:32 ART

To configure Auto-RP in a sparse-mode env do the following
   
  1) Configure rp address for the global groups on all the routers participating in multicast using the following command
        ip pim rp-address x.x.x.x 1
        access-list 1 permit 224.0.0.39
       access-list 1 permit 224.0.0.40
   
  2) Configure the rp address for the local groups on the RP router using
      ip pim send-rep-announce lo 0 scope 16 group-list 1
      access-list 1 permit 239.0.0.0 0.255.255.255
   
  3) Configure the rp mapping agent on another router that has good connectivity to all routers in the multicast domain using
    ip pim send-rp-discover scope 16
   
  All the interfaces should have "ip pim sparse-mode" configured.
   
  So the difference between sparse-mode and sparse-dense-mode is that we need to define the rp address for the default groups on all the routers.
   
  Also keep in mind that when you are deploying this over a frame-relay network on the hub router configure " ip pim nbma-mode" to allow it to distribute the rp mappings to all its spokes.
   
  HTH
  Shiv

Mathew Fernando <mathewfer@gmail.com> wrote:
  Hi Group,

I setup a LAB scenario with a hub-and-spoke topology where there are 3 spoke
routers and 2 of the spokes has another router behind.
The hub router uses FR sub-interfaces for 3 spoke routers.

RIP is configured on all the interfaces on all the routers and PIM SPARSE
mode is configured on all the interfaces.
AUTO-RP is configured on the HUB router who acts as the RP as well as the
mapping agent. No filters are applied for the groups in RP or mapping agent
configs.

When I say "show ip pim rp mapping", it shows the RP IP (of the hub router)
on all the spoke routers except on the 2 routers behind the spoke routers.

MY QUESTION IS: I do not understand how these 3 spoke routers learn the
AUTO-RP when there is no DENSE mode (or sparse-dense) configured.

Also the command "ip pim autorp listener" is not configured on any of the
routers. I understand why these 2 routers behind the spoke does not see the
AUTO-RP (because there is no DENSE configured). IOS on all the routers are
12.2T.

Can someone please explain how this works?

Thanks in advance

mathew

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