[Dnsmasq-discuss] dnsmasq not overriding leases for static assigments

Geert Stappers stappers at stappers.nl
Sun May 16 14:06:58 UTC 2021

On Sun, May 16, 2021 at 02:13:37PM +0100, Jesus M Diaz wrote:
> On Sun, 16 May 2021 at 13:48, Kristof Burek wrote:
> > >  ....
> > How do you know that the client is requesting the same IP address?  (Have
> > you been able to sniff the packets?)  Does the client "know" when its MAC
> > address has changed?
> That's an easy one,

Okay.  Here other easy one:  Reply below previous text.

> I have the 'old' lease, the dnsmasq config and logs,
> and tcpdump sniffing (see below). But the short story is:
>    1. device asked some time ago for an ip-addr, and as it is configured to
>    get a static one, it got it (logged in the 'old' lease)
>    2. device disconnect from the router and connects to one AP, and after
>    reconnecting, request the same ip-addr with a new mac-addr

a.k.a.  DHCP renewal

>    3. dnsmasq sees the 'old', and before even checking anything else (I
>    know this because there are no 'tags' assigned to the device), respond with
>    'address in use'

Actual "IPv4 address in use"

>    4. device requests for a new ip-addr with the new mac-addr

That new MAC address is the root cause of the "problem".

>    5. dnsmasq identify the client (assigns the tags 'known' -it is in the
>    config file-, 'eth0' -interfaz-, 'mobile' -assigned to this device in the
>    config file- and 'pasillo' assigned in the config file to all devices
>    connected to that AP.

I don't understand that   .  I think it tries to explain "available IPv4
address in best fit dhcp-range".

>    6. dnsmasq, despite having identified the client,

And how did that identification happen???

>    assigns a new ip-addr because the old one is in use.

Which is good.

Geert Stappers
Silence is hard to parse

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