mclt Values, was 2 Instances of dhcp on Same Platform

[David W. Hankins]

On Mon, Feb 26, 2007 at 06:35:41AM -0600, Martin McCormick wrote:
> 	On rare occasions, the secondary came up to normal within
> a few seconds.  I think I saw once where the primary came
> immediately back up, but I never got out of one of those
> transactions without at least one MCLT wait.  Our sites are very
> busy as I am sure yours are.  On the day in question, we had 1,269,677
> lines of dhcpd messages.

There's a bit of code that 'forgoes' the MCLT wait (I never liked
the way it does this - it plays with STOS) in the case where:

1) The local server is entering 'recover'.
2) The local server was previously in 'shutdown'.
3) The remote server is in 'partner-down'.
4) There are no updates queued.

In these cases, it's reasonably safe to transition immediately to
normal (I seem to recall the draft actually describes this).

At your level of activity, there are always going to be
updates queued, unless the DHCP servers lose connectivity
with clients (but not each other) before the shutdown, or
other 'weird corner cases'.

So I suspect what needs to happen is for the similar limit to
be reapplied on the exit -  when the update queue goes empty.

> 	Again, thanks for any thoughts.  When we had failover
> going, it was otherwise very good.  As I mentioned last week, the
> final blow was when we discovered that our present wireless
> network authentication devices could only talk to one dhcp server
> of the pair.

This must be in my email backlog somewhere.  We had a company
festival of sorts last week, so I've been away from the keyboard.

-- 
ISC Training!  http://www.isc.org/training/  training at isc.org
Washington DC area, April 16-20 2007.  DNS & BIND, DDNS & DHCP.
-- 
David W. Hankins	"If you don't do it right the first time,
Software Engineer		you'll just have to do it again."
Internet Systems Consortium, Inc.	-- Jack T. Hankins