[Dnsmasq-discuss] DHCP Request Flood

Simon Kelley simon at thekelleys.org.uk
Wed Mar 4 20:53:35 GMT 2015


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On 25/02/15 09:14, Gavin Hill wrote:
> As a quick update, I tried changing
> 
> dhcp-range=192.168.1.1,192.168.1.99,static,48h
> 
> to
> 
> dhcp-range=192.168.1.1,192.168.1.99,static,infinite
> 
> Things slowed down a little and I’m seeing fewer log entries, but
> it still doesn’t explain why the 48h entry didn’t seem to work.
> I’m assuming 48h is a valid syntax?
> 

48h is valid syntax.

You need to set log-dhcp in the configuration and examine the logs to
see what lease length the clients are requesting and being given.

This may be client oddness, rather than server oddness.

Cheers,

Simon.




> 
>> On 24 Feb 2015, at 10:31 AM, Gavin Hill <gavin at highpeak.co.za>
>> wrote:
>> 
>> I’m using dnsmasq on a Raspberry Pi as a DHCP and DNS server for
>> my home network.  I switched to using the Pi as it boots fast and
>> dnsmasq can start handing out IP addresses on my network quickly
>> after a power failure (IP cameras, alarms system, etc).
>> 
>> Network: 192.168.1.0/24 Range 1-99 static, defined in
>> /etc/dnsmasq.d/reservations file Range 100-250 dynamic
>> 
>> If I check my syslog though, I see many of my static devices
>> requesting IP addresses every 60 seconds or so, suggesting their
>> leases are only 120 seconds.  I’ve searched for the issue but the
>> only hits I could find were related to windows machines looking
>> for and autoconfig option (option 252).  While I’ve added that
>> option, many of the requests are not coming from Windows machines
>> anyway.
>> 
>> dhcp-range=tag:!known,192.168.1.100,192.168.1.250,12h
>> #Dynamic devices dhcp-range=192.168.1.1,192.168.1.99,static,48h
>> #Static devices in /etc/dnsmasq.d/reservations e.g.
>> dhcp-host=00:0c:5d:dc:4f:3c,192.168.1.52,cctv-ptz
>> 
>> 
>> Feb 24 10:15:13 ipam dnsmasq-dhcp[23224]: DHCPREQUEST(eth0)
>> 192.168.1.52 00:0c:5d:dc:4f:3c Feb 24 10:15:13 ipam
>> dnsmasq-dhcp[23224]: DHCPACK(eth0) 192.168.1.52 00:0c:5d:dc:4f:3c
>> cctv-ptz [may repetitive entries removed] Feb 24 10:16:10 ipam
>> dnsmasq-dhcp[23224]: DHCPACK(eth0) 192.168.1.52 00:0c:5d:dc:4f:3c
>> cctv-ptz Feb 24 10:16:14 ipam dnsmasq-dhcp[23224]:
>> DHCPREQUEST(eth0) 192.168.1.21 00:20:4a:a8:28:fe
>> 
>> 
>> Regards Gavin
>> 
>> -- Gavin Hill – gavin at highpeak.co.za
>> <mailto:gavin at highpeak.co.za> – http://www.highpeak.co.za
>> <http://www.highpeak.co.za/> -- @HighpeakHA
>> 
>> 
>> 
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> 
> 
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