From: ccie2be (ccie2be@nyc.rr.com)
Date: Tue Jul 20 2004 - 21:44:08 GMT-3
Gerry,
There is something that's very confusing but that you should understand.
This sounds like a contrdiction and I don't fully understand all the
details, but...
The mode of the interface DOES NOT determine whether a mcast group runs in
sparse or dense mode.
Let me say that again.
The mode of the interface DOES NOT determine whether a mcast group runs in
sparse or dense mode.
What determines if a group if sparse mode or dense mode is whether or not
the router knows of a RP for the mcast group.
If the location of the rp for a mcast group is known, that mcast group runs
in sparse mode, otherwise it runs in dense mode.
I'd explain why this is except that I don't remember. It is, however,
explained in Beau Willianson's book Developing IP Multicast Networks.
Personally, I don't think the issue of what mode to use on the interface is
something to be too concerned about. I think that part of the mcast section
won't be difficult to figure out from the lab instructions and will most
likely be fairly obvious.
But, I think you should understand very thoroughly the differences between
BSR and Auto-rp and when each method needs to be used. It's my sense that
the lab can be worded in such a way that knowing whether to use BSR or
Auto-rp can be extremely non-obvious.
Also, I seem to recall that Scott Morris has written many posts on this
topic. I suspect that if you do a search on Scott Morris and Multicast,
you'll find a goldmine of helpful info.
HTH, Tim
----- Original Message -----
From: "Gerry Hilton" <gerry.hilton@rogers.com>
To: "Kenneth Wygand" <KWygand@customonline.com>
Cc: <ccielab@groupstudy.com>
Sent: Tuesday, July 20, 2004 7:45 PM
Subject: Re: Multicast - Sparse Mode
> Hi. I agree - if it is clearly stated to configure sparse mode, and
> there are no other requirements, then I too would configure sparse mode,
> and probably use the ip pim auto-rp listener command.
>
> In my email though, I was referring to the less clear case where there
> were additional requirements so that configuring sparse mode only would
> probably not work. I keep reading that interfaces are treated as sparse
> if they know of an RP, so in that case I was thinking that configuring
> them as sparse-dense and making sure that an RP was known, would meet
> the requirements of sparse mode as well as some additional requirements.
>
> Thanks,
> Gerry
>
> Kenneth Wygand wrote:
>
> >Gerry,
> >
> >My opinion... If "one is asked to configure sparse mode", hey, you'd
better be configuring SPARSE mode... not Dense mode, not Sparse-Dense mode,
but SPARSE mode... This is just my opinion.
> >
> >However, take a look at the following command in the Doc CD:
> >
> >"ip pim auto-rp listener"
> >
> >It may answer some of your question for things that previously "required"
dense-mode...
> >
> >HTH,
> >Ken
> >
> >________________________________
> >
> >From: nobody@groupstudy.com on behalf of Gerry Hilton
> >Sent: Tue 7/20/2004 7:12 PM
> >To: ccielab@groupstudy.com
> >Subject: Multicast - Sparse Mode
> >
> >
> >
> >Hi there. A few questions about multicast and sparse mode:
> >
> >If one is asked to configure sparse mode, then is it valid to configure
> >ip pim sparse-dense mode and have a known RP, as then the interfaces
> >would be treated as sparse mode (this would be if there was a case where
> >just configuring sparse mode would not meet all requirements)?
> >
> > If the interfaces are configured as sparse-dense and the RP is known
> >via auto-RP, then are they still considered to be acting in sparse
> >mode? If not, then is the only way to know the address of the RP and
> >still be considered sparse mode, to manually configure the RP address on
> >each router?
> >
> >This is only in the case where one requires the interfaces to be
> >configured in sparse-dense mode but treated as sparse.
> >
> >Thanks,
> > Gerry
> >
> >_______________________________________________________________________
> >Please help support GroupStudy by purchasing your study materials from:
> >http://shop.groupstudy.com
> >
> >Subscription information may be found at:
> >http://www.groupstudy.com/list/CCIELab.html
> >
> >_______________________________________________________________________
> >Please help support GroupStudy by purchasing your study materials from:
> >http://shop.groupstudy.com
> >
> >Subscription information may be found at:
> >http://www.groupstudy.com/list/CCIELab.html
>
> _______________________________________________________________________
> Please help support GroupStudy by purchasing your study materials from:
> http://shop.groupstudy.com
>
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
This archive was generated by hypermail 2.1.4 : Sun Aug 01 2004 - 10:11:59 GMT-3