2 dhcpd Instances on Same Platform? Take 2

John Wobus jw354 at cornell.edu
Thu Feb 22 14:22:03 UTC 2007

> I'm curious as to why you have MCLT issues when restarting the servers.
> I have run several large sites with failover, and we always used the
> procedure to stop and then start the secondary. Wait for it to sync
> (usually only a few seconds), then stop and start the primary. Both
> servers continue to hand out leases with the normal lease times after
> restarting this way.
> By normal I mean that the initial lease offered to a client is MCLT and
> then subsequently it goes to the default lease time. But unless a
> client tries to renew during the few seconds the server was shutdown
> things operate normally. In fact if the client tries to renew when the
> server is down, it will usually retry a short time later and because
> the server is back up, things keep on working.
> And it's good to see someone so dedicated to a project. Wow! 1993 must
> havc been pre1.0 code... Way to go.
> regards,
> -glenn

We also restart our servers frequently, careful to do the two servers 
and see no such problems.  We reconfigure the server "while you wait" 
to a maximum
frequency of once every two minutes.  This exercises the daemons' 
ability to handle
stops/starts to a high degree.  Size wise, we have 60,000 statically 
clients, and 33,000 dynamic addresses, of which perhaps 4,000 might
be active at busy times.

We see a very small number of leases become inconsistent between the
two servers, and remain that way for days, but generally, the setup 

John Wobus

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