Dhcpd Frequent Renewals

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This might be the wrong place to ask, but I don’t know where to turn. My internal home network, including wireless, is controlled by a CentOS6 server, which provides dhcpd services, along with NAT. I
have DHCPD configured with the addresses through as the range for dynamic allocations. The default-lease time is 1800 seconds, the maximum is 3600 seconds.

My windows clients, and even an ipad-mini behave nicely, asking for DHCP renewals once ever five minutes, or at about 80% of the default lease time, a behavior I can understand. However, several of my guests, with their own iPads, I-watches, iPhones, connect to my network (via a wireless access point which does not do routing functions) and they’re renewing once every 20-30 seconds. In addition, these devices also loose connectivity for brief intervals, which seems to be roughly synchronized with dhcp renewal. This last fact I deduce by doing “tail -f /etc/log/messages” and hearing them say “lost connection” at just about the same moment the DHCPREQUEST
and DHCPACK statements show up.

It’s difficult to believe that Apple IOS devices (all of which are running apple’s latest) have a dhcp client problem not shared by windows or even linux hosts.

Does anyone have any clues?

David Kurn San Francisco

DHCPD.CONF file is excerpted below:


3 thoughts on - Dhcpd Frequent Renewals

  • does your dhcpd update the dns? name resolution for devices seems to be required for some applications and thus the dns needs to know about the leases. Have you checked your dhcpd log entries and your dns log entries? I have had situations where the dhcpd lease is dropped due to not being able to complete dns update of the info – thus the client retries again and again – they do get onto the internet but the connection drops and a new lease is requested, HTH

  • Rob DNS service for my clients is provided by my gateway server, the same machine as the DHCPD server. I think that’s what the “option domain-name-servers” line does. This allows me to provide 192.168
    addresses to them when they try to access anything inside the house with a name. If it’s not a locally defined name, BIND forwards the request to the internet.

    I’m not sure I understand about dhcpd log and dns log. I scan
    /var/log/messages, using the service name as the key. Looking at
    ‘named’ entries, all I see are messages of the form
    “clients-per-query increased to XX”. I’m still mystified by the fact that only the i-devices (iphone, ipad) exhibit this behavior of rapid dhcpd renewals. Mac’s and PC’s don’t.


    At 06:48 AM 2/17/2016, you wrote: