combining lease files

project722 project722 at
Wed Aug 29 14:13:51 UTC 2018

Thanks for the feedback guys!

So, in this scenario I'll have 2 masters temporarily - B will become a new
master and sync to A-failover, and A-master will still be in the picture as
well? If I try this approach, then, I will have to add the subnets for
server B to A-failover, then enable failover between B and A-failover?
Wouldn't A-master have a problem with A-failover having subnets in its conf
file that A-master doesn't?

Also, I'm starting to think aboout ip helper addresses. Seems like the flow
would be:

Add an IP helper address on the router for server B's subnets to also point
to A-failover
Once they are completely in sync then remove the IP helper for server B
altogether and add another for A-master

Does that sound about right?

On Wed, Aug 29, 2018 at 8:36 AM Bob Harold <rharolde at> wrote:

> On Wed, Aug 29, 2018 at 9:33 AM Sten Carlsen <stenc at> wrote:
>> On 29/08/2018 14.28, project722 wrote:
>> Hey All,
>> We are consolidating all subnets on server B and moving to an exisitng
>> failover pair we have, In order to decom server B. I'll need to take the
>> leases file from server B and combine whats there with the leases file on
>> both servers in the failover pair. (doing this to make the failover pair
>> aware of what leases are already out there that were assigned by server B)
>> I am not sure, but I think one other way could be to make server B part
>> of a failover pair with one of the existing failover servers for a period
>> of time. That way the remaining server will have all the information
>> transferred from server B. Later that configuration could be changed to
>> have the other remaining failover server act as the peer, that way the
>> servers would transfer the data, probably with less risk.
>> Others should confirm or reject this idea.
>> I'm thinking just a simple cat on both files should be fine to combine
>> the data. And, all 3 servers are running the same verison of dhcp
>> ( and RHEL so I don't expect and formatting problems.
>> However, since failover pairs have more transitional states with the
>> "binding state" variable, is it possible I will run into any issues doing
>> this? Is there a better, more preferred way of doing this instead of
>> merging the leases file?
> The benefit of a failover pair is that we can upgrade/repair/replace one
> server at a time without any interruption in service.
> Let's call the failover pair A-master and A-failover.
> The recommended method is to configure server B as master and the
> A-failover server as failover for server B's subnets also.  Give it some
> time (watch the failover messages in the logs) to sync the data from B to
> A-failover.  Then move the subnets from B to A-master, and A-master will
> sync the data from A-failover.
> --
> Bob Harold
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> dhcp-users at
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