[Dnsmasq-discuss] OpenWRT, modem restarts and lost dhcp leases

[Dave Taht]

The simplest thing to do is merely move the dhcp leases file to
persistent storage, if you are willing to live with the long term
failure mode of flash becoming less long term. I don't honestly know
the cycle lifetime of low end flash chips anymore - it was very bad
when they first came out but has improved dramatically in the last 10
years.

On Fri, Aug 22, 2014 at 11:39 AM, Anatol Pomozov
<anatol.pomozov at gmail.com> wrote:
> Hi
>
> This is a follow-up for a discussion that I had in systemd maillist
> [1]. Here is description of the problem:
>
> I have a router (Archer C7 V2) where I use patched version of OpenWRT.
> It uses dnsmasq as a dhcp server for my local network. OpenWRT uses a
> file on tmpfs to store the dhcp leases. When I reboot modem the files
> on tmpfs are lost and dnsmasq needs to build the dhcp lease database
> from anew. All the machines that are connected directly to the modem
> (via cable or via wifi) work fine here - they notice that data link
> went down and when it gets back they update DHCP information.
>
> The problem is when some machine is located in a different network
> segment. In this case the data layer stays healthy, machine does not
> notice anything wrong with the network and dhcp client does not update
> DHCP lease at the router. So I cannot ping my machine by the name
> anymore, pinging by ip works fine. To update the lease I need to power
> cycle the ethernet switch that serves that network segment. But of
> course it is not the best solution.
>
> So my question what is the solution for such problem? Should dnsmasq
> ask on start all the machines to update their dhcp leases? Is it what
> FORCERENEW option is? I see that FORCERENEW is not implemented in
> dnsmasq.
>
> [1] http://lists.freedesktop.org/archives/systemd-devel/2014-August/022363.html
>
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-- 
Dave Täht

NSFW: https://w2.eff.org/Censorship/Internet_censorship_bills/russell_0296_indecent.article