long expired DHCPD leases still in dhcpd.leases file

[schilling]

Thanks for the clarification. After reading your reply, I also found the
following past thread which has more details.

how dhcp-server select a ip-address to client?
https://lists.isc.org/pipermail/dhcp-users/2012-March/015052.html

Best,

Schilling


On Fri, Dec 15, 2017 at 3:25 AM, Glenn Satchell <glenn.satchell at uniq.com.au>
wrote:

> The dhcp RFCs state that a DHCP server must try hard to return the IP
> address a client previously used. So when the leases file is periodically
> re-written the newest lease for each IP address is retained.
>
> If required, the DHCP server will hand those IPs out to a new client if
> there are no other free leases available.
>
> All it indicates is that you have enough free IP addresses in the dynamic
> ranges so the server has not needed to use those old ones.
>
> I guess you could clean them out if you knew (or didn't care) if that
> client was coming back. In that case, stop the dhcp server, modify the
> leases file, then start it up again. I imagine you would want a script to
> do the editting quickly.
>
> regards,
> -glenn
>
>
> On Fri, December 15, 2017 5:22 pm, Bill Shirley wrote:
> > What "cleaning" do you expect?  If those addresses are still defined in
> > dhcpd.conf
> > the DHCPD will keep track of them no matter when they were last used.
> >
> > Bill
> >
> >
> > On 12/14/2017 4:04 PM, schilling wrote:
> >> When DHCPD write lease from memory to disk, there is no cleaning done?
> >> Or I am missing a configuration flag for that?
> >>
> >> We have one pair of DHCP servers which have been migrated several times
> >> to new pairs over the years. Currently running on
> >> RHEL7 with DHCP 4.2.5. We recently found out that there are a lot of
> >> expired leases from several years ago are still in the
> >> lease file. For example, there are about 2 millions leases in the file,
> >> but 32K leases have lease ends times in 2014, 2015,
> >> and 2016.
> >>
> >> We had database out of sync from secondary to primary issue, namely,
> >> both member is claiming the other member is holding all
> >> the free leases. It will get fixed after "faulting the database"
> >> https://kb.isc.org/article/AA-00609/0/How-do-I-
> resynchronize-a-failover-pair.html.
> >> We are suspecting these leases might
> >> contribute to the issue.
> >>
> >> Best,
> >>
> >> Schilling
> >>
> >>
> >>
> >>
> >>
> >> _______________________________________________
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> >> https://lists.isc.org/mailman/listinfo/dhcp-users
> >
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>
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