From: Brian McGahan (bmcgahan@internetworkexpert.com)
Date: Fri Sep 05 2003 - 13:26:30 GMT-3
You can run auto-rp with pim sparse mode. The reason that it is
most common to run sparse-dense mode with auto-rp is like Jeff
mentioned, due to the mapping-agent and the auto-rp announcements.
The RP-announce (from the RP itself) and RP-discovery (from the
mapping agents) messages are sent as a multicast to the groups
224.0.0.39 and 224.0.0.40. Since sparse mode dictates that in order to
join a group you must have an RP, you first need to know who the RP is
in order to find out who the RP is. Since this is recursive, there are
two ways to fix it.
With sparse-dense mode, groups with an RP will be sparse, while
groups without an RP will be dense. Therefore, when you 'show ip
mroute', you will see that 224.0.1.39 and 224.0.1.40 are dense:
(*, 224.0.1.39), 00:00:17/stopped, RP 0.0.0.0, flags: D
Incoming interface: Null, RPF nbr 0.0.0.0
Outgoing interface list:
Serial1/3, Forward/Sparse-Dense, 00:00:17/00:00:00
Ethernet0/0, Forward/Sparse-Dense, 00:00:17/00:00:00
(*, 224.0.1.40), 00:00:56/00:02:35, RP 0.0.0.0, flags: DCL
Incoming interface: Null, RPF nbr 0.0.0.0
Outgoing interface list:
Serial1/3, Forward/Sparse-Dense, 00:00:56/00:00:00
Ethernet0/0, Forward/Sparse-Dense, 00:00:56/00:00:00
The other option is to statically configure a default RP for
these groups.
ip pim rp-address 1.1.1.1 1
access-list 1 permit 224.0.1.39
access-list 1 permit 224.0.1.40
Now devices in the PIM domain can join these groups, and listen
for auto-rp messages. One advantage of the latter method is that
devices can not join groups that the RPs are not announcing. So if you
want to ensure that devices are not failing over to dense for groups
that aren't announced, use this method.
HTH,
Brian McGahan, CCIE #8593
bmcgahan@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
Toll Free: 877-334-8987
Direct: 708-362-1418 (Outside the US and Canada)
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
ccie2be
Sent: Friday, September 05, 2003 10:38 AM
To: Group Study; Jeff Wishnew
Subject: Re: PIM-Sparse vs Sparse-Dense
Thanks for that clarification.
----- Original Message -----
From: "Jeff Wishnew" <jwishnew@comcast.net>
To: "ccie2be" <ccie2be@nyc.rr.com>; "Group Study"
<ccielab@groupstudy.com>;
"Roger McNeace" <rmcneace@terremark.com>
Sent: Friday, September 05, 2003 10:31 AM
Subject: Re: PIM-Sparse vs Sparse-Dense
> That's not entirely accurate. Sparse-Dense enables the multicast
routers
to
> find the RPs via Auto-RP. The candidate RPs multicast out their
intent to
> become an RP for particular groups. The Mapping Agents listen for the
> announcements and then multicast out the Group-to-RP mappings. All PIM
> Sparse-Dense routers will listen for the Mapping Agent's Group-to-RP
mapping
> announcements.
>
> On the other hand, BSR uses hop-by-hop broadcast to send out the
Group-to-RP
> mappings. Therefore, you can use strictly Sparse mode when using BSR.
>
> Jeff Wishnew
> CCIE #12148
>
>
> ----- Original Message -----
> From: "ccie2be" <ccie2be@nyc.rr.com>
> To: "Group Study" <ccielab@groupstudy.com>; "Roger McNeace"
> <rmcneace@terremark.com>
> Sent: Friday, September 05, 2003 9:26 AM
> Subject: Re: PIM-Sparse vs Sparse-Dense
>
>
> > The sparse-dense mode, as I understand it, is so that all the
multicast
> > routers find out who the RP's are automatically via either Auto-RP
or
BSR.
> > If the routers are only sparse mode, then you have to manually
configure
> the
> > address(es) of the RP's on each router.
> >
> > For further info, see either Beau Williamson book, Developing IP
Multicast
> > Networks, Chapter 12 or Dolye's Routing TCP/IP volume II.
> >
> > HTH, dt
> >
> > ----- Original Message -----
> > From: "Roger McNeace" <rmcneace@terremark.com>
> > To: <ccielab@groupstudy.com>
> > Sent: Friday, September 05, 2003 9:27 AM
> > Subject: PIM-Sparse vs Sparse-Dense
> >
> >
> > > As I understand it by default on Cisco routers PIM-Sparse mode
will
> > > automatically switchover to a SPT (dense mode) to a source since
the
> > > threshold is set to 0. Why and when would I need Sparse-Dense if
Sparse
> > > alone does the same thing?
> > >
> > >
> > >
This archive was generated by hypermail 2.1.4 : Wed Oct 01 2003 - 07:24:23 GMT-3