Unknown client alerts and clients not getting IP addresses

Fleming, Tony t.fleming at tcu.edu
Mon Aug 22 22:30:18 UTC 2016

Good afternoon folks!
We ran into a problem today and it has me completely dumfounded
                We create a host record for each device that connects to our network
                Over the years our dhcpd.conf file has grown due to little purging (yeah - I know we should be purging the data)
                Suddenly today, we began getting reports users are unable to get an IP address.
                The clients vary from iphones, to OS X and PC laptops
                                The issue doesn't seem to be OS or hardware dependent
                My logs are alerting:
                                dhcpd: DHCPDISCOVER FROM xx:xx:xx:xx:xx:xx via x.x.x.x: uknown client
In my dhcpd file there is a "host" record for each device - so I am scratching my head to why the device isn't getting an IP address.
                Not all devices are having trouble getting IP leases
                We have removed the directive in dhcpd.conf to "deny unknown clients"
                Now all of our devices are getting IP addresses.

                Has anyone experienced a problem like this?
                                If so, what did you find to be the root cause?
                Is it possible my 300k line dhcpd.conf file is causing this behavior?
                                Could there be a programmatic time-out searching through host records in memory that is causing the host lookup to fail?

Thank you.

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