howto change range in ha-setup?

John Wobus jw354 at
Fri Mar 12 20:27:37 UTC 2010

On Mar 9, 2010, at 5:28 PM, Glenn Satchell wrote:

> On 03/10/10 02:27, Nils-Henner Krueger wrote:
>> What is the recommended way to alter a range definition in a ha
>> configuration?
>> I'm running version 4.1.1 with failover configuration. Due to  
>> external
>> circumstances I will have to expand the ranges inside of subnet
>> configuration entries. This should be done with minimal  
>> interruption of
>> dhcp availability. What is the best way to achive this? I know that I
>> will have to restart the ha members for activating the change.  
>> Should I
>> restart down both servers at the time, or is it possible to to  
>> shutdown
>> only one at a time (by using the control object to inform the other
>> member) and restart it with the new configuration bevor taking down  
>> the
>> second one? Will I run into trouble with an inconsistent range
>> definition between the ha members? Will this be fixed as soon as I  
>> have
>> restarted both members?
>> Thanks for ideas.
>> nils-henner
> I have done this many times. Modify dhcpd.conf on both servers. Then
> stop dhcpd using your normal procedure and start it on the secondary,
> check that it is serving requests correctly, then stop and start the
> primary.
> I normally try to do the two restarts within a few minutes of each
> other. As long as one server is running then new requests will be  
> served
> by that server. Any client trying to renew to a specific server will
> retry if it happens to send a request while that server is restarting.
> The reason I do the secondary first, was that if you add new subnets  
> and
> restart the primary first then it communicates this to the secondary
> which logs a whole bunch of errors about unknown subnets. For changing
> ranges this may not be a problem, but I just made it a consistent
> procedure to avoid problems. This may no longer be the case with 4.x
> versions.
> -- 
> regards,
> -glenn

We change ranges and subnets all the time, creating our entire
configuration from an administration database, and our "reload"
script restarts one server before stopping the other.  However, we
make no distinction between a primary and a secondary in
choosing our order.

Is this really an area in which the primary and secondary are not
specific?  I gather from what you say that upon restart, the primary
initiates some inter-server communication that the secondary
would not.


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