howto change range in ha-setup?

Glenn Satchell glenn.satchell at
Tue Mar 9 22:28:29 UTC 2010

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 

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 

Glenn Satchell                            |  Miss 9: What do you
Uniq Advances Pty Ltd, Sydney Australia   |  do at work Dad?
mailto:glenn.satchell at         |  Miss 6: He just tel:0409-458-580   |  types random stuff.

More information about the dhcp-users mailing list