From: Lord, Chris (chris.lord@lorien.co.uk)
Date: Mon Aug 09 2004 - 11:11:49 GMT-3
I still don't really get this.....
Ok, I understand that it is rp mapping cache that determines whether the group should operate in SM or DM, right. So in my example there is no mapping for 224.3.3.3 so the router will try to use DM for this group and SM for the others. It is my understanding that the interface config then steps in and says "I know you would like to use DM but I only support SM so you can't"
Take Auto-RP for example. You cannot use this if you have only have SM on all of your interfaces. You have to use SDM so that the rp-announce and rp-discover process can fall-back to DM. If a router was free to choose between SM and DM regardless of the Interface config you wouldn't have this constraint on using Auto-RP.
(I know these days there is an RP listener option which gets around this but I'm ignoring that for the purpose of the current discussion)
Regards,
Chris.
-----Original Message-----
From: ccie2be [mailto:ccie2be@nyc.rr.com]
Sent: 09 August 2004 15:00
To: TAN CHOH KOON; Lord, Chris; ccielab@groupstudy.com
Subject: Re: PIM-SM
Hi,
Can anyone elaborate on the following by explaining the difference in how an
interface operates depending on mode setting (sparse or dense or
sparse-dense)?
Interface Mode
Determines how the interface operates when sending/receiving multicast
traffic.
That's never been clear to me.
Thanks, Tim
----- Original Message -----
From: "TAN CHOH KOON" <tckoon@pc.jaring.my>
To: "Lord, Chris" <chris.lord@lorien.co.uk>; <ccielab@groupstudy.com>
Sent: Monday, August 09, 2004 9:46 AM
Subject: RE: PIM-SM
> Hi Chris,
>
> Answer is if you do not configure static RP for group 224.3.3.3, it
> automatically fall to Dense Mode.
> If you configure static RP for group 224.3.3.3, but let say the RP address
> is non existing in your network. 224.3.3.3 will never fall to DM.
> Configure interface with only Sparse Mode, do not mean it will never fall
to
> Dense Mode.
> It depend on your Group mode. If your configure static RP for that gorup
it
> will never fall back to DM.
> Even the RP is down or not existing !!
>
> If you able to access to Networker 2003 slide, refer to Deploying IP
> Multicast.
>
> Extract from slide
> -------------------
>
> Group Mode vs. Interface Mode
>
> Group & Interface mode are independent.
> Interface Mode
> Determines how the interface operates when sending/receiving multicast
> traffic.
> Group Mode
> Determines whether the group is Sparse or Dense.
>
> Group Mode
> Group mode is controlled by local RP info
> Local RP Information
> Stored in the Group-to-RP Mapping Cache
> May be statically configured or learned via
> Auto-RP or BSR
> If RP info exists, Group = Sparse
> If RP info does not exist, Group = Dense
> Mode Changes are automatic.
> i.e. if RP info is lost, Group falls back to Dense.
>
>
> Configuring Interface
> Interface Mode Configuration Commands
> Enables multicast forwarding on the interface.
> Controls the interfaces interfaces mode of operation.
> ip pim dense-mode
> Interface mode is set to Dense mode operation.
> ip pim sparse-mode
> Interface mode is set to Sparse mode operation.
> ip pim sparse-dense-mode
> Interface mode is determined by the Group mode.
> If Group is Dense, interface operates in Dense mode.
> If Group is Sparse, interface operates in Sparse mode.
>
>
> Regards
>
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