[Dnsmasq-discuss] can't take away IPv4 address

Uwe Schindler uwe at thetaphi.de
Wed Aug 26 08:37:08 BST 2015

Hi Harald,

> > Dnsmasq does the check which the standards require, which is to send
> > an ICMP ping (echo request) to the address it's about to allocate. The
> > fact that the client doesn't respond would seem to indicate that the
> > clients are NOT using IP addresses after the lease has expired.
> >
> I think the ping test would be pretty helpful.
> The IPv4 address range is set to Lease time is 1h.
> There are less than 200 DHCP clients in my net. Even without ping test it
> should be easy to avoid a conflict.

The problem with a ping test is: Most clients using a firewall (especially the Windows Firewall) block pings by default (which is horrible, just my personal opinion). So just throwing away the address may not work in all cases. But what can be done: If the lease expires and was not renewed by the client and client cannot be pinged anymore, then it could be removed from the leases.

The problem with ARP tables getting out of date is more Linux-Kernel specific. Dnsmasq does not really deal with ARP tables.


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