From: Daniel C. Young (danyoung99@xxxxxxxxxxxx)
Date: Sat Aug 18 2001 - 13:43:26 GMT-3
Hi Jay, see comments:
> Q1: is that all needed to configure ? auto-rp .. I am able to
> ping this multicast group
Jay, you are missing the 'ip pim send-rp-discovery' command. You need this
to configure the hub routers as mapping-agents. Recall that mapping agents'
role is to discover all the C-RPs (candidate RPs), hold an election and
multicast out the winner to all the other routers. Anyway, all this
discovery must been done under dense-mode. Think about it, you need to know
of an RP to send traffic, but to learn of an RP you need to know who the
source is... Doesn't work, that's why auto-rp requires you to have
sparse-dense mode.
That being said, I'm very curious to know why you said you can ping those
multicast groups. With certain releases of 12.0, even when you configure
sparse-mode, the code will actually run sparse-dense mode, which means that
if the rp is not discovered, your routers will actually use dense mode. Do a
'show ip mroute' and look at your (*,G) and (S,G) entries. Do they make
sense? Are you getting 'D' flags? If so, then you're running dense mode.
When you ping, do you get a response from all the members?
> Q2: I have added ip pim nbma mode on the hub router. Is this
> configuration necessary ?
This configuration is for effeciency. When configured, the router will
maintain next-hop information in the (*,G) and (S,G) outgoing interface list
in addition to the interface. This is so that the hub can maintain a
detailed list of all the spoke routers membership status. Without the
command, the hub only binds (*,G) and (S,G) entries to the outgoing
interface, which means that it will send out multicast traffic out that
interface if even only one of the spoke routers has requested a join. The
interface driver then will copy that packet out and also send it to the
other spokes, even though they have no active memebers on them. Not very
efficient at all.
I hope that helps. Feel free to email me directly off line for
multicasting-type questions.
Regards,
Daniel Young
CCIE #7999
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