All things related to multicast

[Stig Venaas <>]

On Tue, Nov 30, 2004 at 11:11:36AM -0600, John Kristoff wrote:
> On Tue, 30 Nov 2004 12:35:26 -0800 (PST)
> 
>  wrote:
> 
> > Setting DR priority will only set which router win's DR election - 
> > overriding the normal IP-based election.
> > 
> > If you want faster DR failover, tweak down the PIM hello timers. 
> > This is what is used for a candidate DR to determine that the elected DR 
> > is either alive or dead.
> 
> OK, thanks.  I guess that will have to do.  I thought that I might
> be able to gracefully migrate the DR to another interface, which would
> magically move PIM state by issuing the associated joins and prunes, but
> I guess that is just asking for too much magic.  :-)

Right, so that is another question really. You want to migrate
manually, while Shep is talking about automatic failover.

I must say I'm not sure myself what the answer to your question
is. You're partly talking of failove for receivers. Note that it's
not always the DR that is the last-hop router.

For sending, I think the new DR will immediately start sending PIM
registers. Also for how people may receive from your sources along
a SPT, it's the routing (RPF) that determines which of your routers
it is rooted at, not which is the DR.

At least I think so. I should read the spec to be sure I don't
embarass myself, but I don't have time for that right now.

Hopefully someone will correct me if I'm wrong.

Stig