RE: Multicast Auto-RP

That's a good question! It seems like there's a bit of a documentation error.
You are right on the money! The Cisco AutoRP works on groups 224.0.1.39 and
224.0.1.40. If you check out the Cisco IOS 12.4 Configuration Guide,
Configuring IP Mulitcast
(http://www.cisco.com/en/US/customer/docs/ios/ipmulti/configuration/guide/imc
_basic_cfg_ps6350_TSD_Products_Configuration_Guide_Chapter.html#wp1058990),
it's a little more clear. The Mapping Agents listen to 224.0.1.39 for the
announcements from the candidate RPs and then send out the information over
224.0.1.40.

Good work!

Thanks,

Jacob Uecker
CCIE# 24481

Development Engineer
CCBOOTCAMP - Cisco Learning Partner (CLP)
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-----Original Message-----
From: nobody_at_groupstudy.com on behalf of Cisco League
Sent: Fri 7/24/2009 5:27 AM
To: Cisco certification
Subject: Multicast Auto-RP

Dear Group,

I am reading this from one of the Multicast Workbook.

Auto-RP

1-
The candidate RP (cRP) sends UDP packets to IP/PORT 224.0.1.39/496 with the
list of groups serviced by this particular RP.

The cRP announces are flooded across the network and reach special routers
called Mapping Agents (MA). Agents listen on 240.0.1.39 and collect all
announcements from candidate RPs.

Question:-
If cRP was sending multicast on 224.0.1.39 should not the MA be listening on
224.0.1.39 rather than 240.0.1.39?

2-
MA starts sending "RP discovery" messages to multicast address 224.0.1.40
port 496.
All regular routers join the multicast group 240.0.1.40 and listen to the
discover message.

Question:-
If MA was sending multicast on 224.0.1.40 should not the routers be joining
224.0.1.40 rather than 240.0.1.40?

It may be a gap in my understanding but I am very conused. Please help me
clarify this.

Thanks and Regards,
CiscoLeague

Blogs and organic groups at http://www.ccie.net
Received on Fri Jul 24 2009 - 05:41:34 ART