All things related to multicast

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.

Greg

On Tue, 30 Nov 2004, John Kristoff wrote:

> I have a situation where I have a pair of Cisco routers attached to the
> same edge LAN segment in a redundant configuration.  I'd like to try to
> minimize packet loss when one of the routers is intentionally brought
> down for maintenance activity.  In my case there will more likely be
> high-rate multicast receivers on the edge segment rather than sources,
> but reducing sender loss/latency is probably most important.
> 
> I see that my recent IOS code there is a 'ip pim dr-priority <#>' option
> in interface mode only.  In a cursory search it appears that IOS XR has
> a global option so hopefully that is on the horizon for existing trains
> of code.  In either case I was planning on testing this option to see
> what I can expect during planned maintenance activities, but thought I
> would check with folks here to see if this is the right and worthwhile
> path to go down.
> 
> Is there a better way to minimize or eliminate multicast forwarding loss
> in a scenario such as this?  It's not clear to me exactly what will
> happen in real-time situations when the DR priority is changed from one
> interface to another.  Any pointers to PIM join/prune state examples
> when a new DR priority is announced by a peer interface.  I presume the
> new DR priority will be announced during the next random interval.
> 
> John
>