From: Joseph Brunner (joe@affirmedsystems.com)
Date: Thu Nov 08 2007 - 02:56:30 ART
I have heard it's because the c-rp messages can't be forwarded by frame
relay spokes, or other nbma network where every end-point may not have a
full-mesh. (Which is why the HUB must be the MA). So if two people on spokes
of an NBMA network want to receive groups the other site is C-RP announcing,
they need a MA (who has pvc's, etc) to each site to do the C-CRP
"reflection" via the discovery messages.
Can any else point me to some good rfc or tech doc goodie explaining this.
Thanks guys!
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
William Nellis
Sent: Wednesday, November 07, 2007 11:58 PM
To: Wollmann, Bruno RQHR; ccielab@groupstudy.com
Subject: Re: OT: Multicast Auto-RP
Going many -> Few then Few -> Many gets around the o^N problem you'll have
in going many -> many...
ie, why does OSPF work the same way w/ having routers advertise LSA to
DR/BDR only to have them readvertise it? Removes full mesh issues...
Realistically... i dunno. Probably has to do w/ limited processing power at
the time AutoRP was invented, and being able to have beefier MA's do the
computations. By having RP's just say "hey, I'm an RP", you can have them
focus on doing RP stuff... like decapsulating registers. Then you have an MA
do calculatoins for (what could be many c-RP), then advertise results of
calculations out to all other routers who just follow orders. Otherwise,
every router has to do calculations. May not be too much of an issue
today... but... autoRP came out in the day of the 2500...
Thats my theory, but yeah, i know what you mean.
-------------------------------------------------------
r/s
William Nellis IV
nellis_iv@yahoo.com
----- Original Message ----
From: "Wollmann, Bruno RQHR" <Bruno.Wollmann@rqhealth.ca>
To: ccielab@groupstudy.com
Sent: Wednesday, November 7, 2007 9:29:19 PM
Subject: OT: Multicast Auto-RP
The document I'm reading right now while studying multicast and auto-rp
says that "all Cisco routers automatically join the Cisco-discovery
(224.0.1.40) group in order to receive group-to-RP mapping information
being multicast by the Mapping Agents in the network". The mapping
agent then advertises the C-RP with the highest IP address as the RP.
My question is, why bother with this step? Why don't the routers just
join the RP-announcement (224.0.1.39) group and learn the candidate RP's
right from the candidates themselves and then chose the one with the
highest IP address on their own. Why not learn it right from "the
horse's mouth" rather than a mapping Agent?
Anyone know the answer or have a logical explanation?
If you want to read what I'm reading for yourself check out page #7 at
ftp://ftp-eng.cisco.com/ipmulticast/training/Module6.pdf
thanks
Bruno
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