Limit DHCP requests with iptables - problem: Router

Simon Hobson dhcp1 at
Wed Aug 29 22:09:19 UTC 2012

Dorsey, Chris wrote:

>We are seeing a lot of induced IO wait due to processing/logging of 
>unwanted DHCP requests from *known* MAC addresses (broken printers, 
>mis-behaving clients, etc.) and were very interested in this thread.


>  or enhancing dhcpd with the ability to allow for 
>administrator-configured filtering.

You can do things like add a host statement with an "ignore booting" 
directive. This should be fairly cheap in processing terms and 
shouldn't clutter the logs.

Also, consider why you are getting IO performance issues. For 
logging, make you you configure the logging as async. The default on 
many setups is sync logging which means a sync (and potentially 
multiple disk writes/seeks) for each log message which will quickly 
consume IO resources.

Simon Hobson

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author Gladys Hobson. Novels - poetry - short stories - ideal as
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