A lot DHCP REQUEST

[sthaug at nethelp.no]

> > I use DHCP ISC on my network architecture, but I have noticed that
> > some clients are sending a lot of DHCP REQUEST, even if the client
> > does ACK for the REQUEST, the log is: 
> >  
> > May  7 05:15:53 dhcp-isc-01 dhcpd: DHCPREQUEST for 190.72.35.198 from 00:30:67:47:a9:f6 (oriana) via 172.17.49.239
> > May  7 05:15:53 dhcp-isc-01 dhcpd: DHCPACK on 190.72.35.198 to 00:30:67:47:a9:f6 (oriana) via 172.17.49.239
> > May  7 05:15:58 dhcp-isc-01 dhcpd: DHCPREQUEST for 190.72.35.198 from 00:30:67:47:a9:f6 (oriana) via 172.17.49.239
> > May  7 05:15:58 dhcp-isc-01 dhcpd: DHCPACK on 190.72.35.198 to 00:30:67:47:a9:f6 (oriana) via 172.17.49.239
> ...
> > Is there any way to avoid this behavior?
> 
> Disconnect the client from the network. ;-)
> 
> The ACK is what the server sends as a reaction to the REQUEST, not
> something the server sees from the client.
> 
> You might be dealing with a retarded client. Do you happen to know what
> operating system and DHCP client software you're dealing with?

I might add that any server that has a sufficiently large and varied
client population is likely to have some clients behaving like this.
It is pretty common, unfortunately. Sometimes a reboot of the client
helps.

Active management, including watching your DHCP server transaction
rates, is important.

Steinar Haug, Nethelp consulting, sthaug at nethelp.no