No subnet declaration; Can't open /var/lib/dhcp/dhcpd.leases for append

Simon Hobson dhcp1 at
Sat Jan 27 21:28:27 UTC 2018

A <publicface at> wrote:

> Sounds reasonable.  And therefore if I was to force it to use enp4s5 somehow, there'd be no subnet for wlp2s0; right?
Probably - but now I understand your network a bit more, I think there are more fundamental problems with your network.

> I did originally have two separate subnets with a /28 CIDR, but I was unable to reach the Internet from blue and someone suggested I have one subnet in order to act as a typical home router. So I reconfigured everything and it's now borked worse than it was.  Said person disappeared shortly after of course.
>> I'm assuming this box is permanently connected to both networks ? If not then it wouldn't be very useful as a DHCP server.
> Yellow - yes.
>> Is there another device bridging the ethernet and WiFi ?
> Not anymore.  There was a virtual bridge using bridge-utils at one point as mentioned above.  Wouldn't be impossible to put it back.
>> I assume there's an AP
> I'm using hostapd as I'm unaware of any other option for AP software at this time.
>> , or it's built into the router - and in that case, you do not need (for DHCP anyway) to listen on the WiFi interface since packets will get bridges to the ethernet interface by the AP.
> There is no commercial router.  Yellow is the router, gateway, access point, dhcp server, dns server, firewall (iptables) and more.

OK, so this box is your gateway, AP, etc, etc. In that case I believe that your setup is fundamentally broken - you have TWO SEPARATE networks (one wired, one wireless) running the same subnet. Thus devices on the wired network cannot talk to devices on the WiFi and vice-verca.

Bear in mind that I've not used WiFi in this manner (I'm used to using external APs), so I am unsure of some of the details. If you want to run a single unified network then you will need to create a bridge, and put the wired and wireless adapters into that bridge - and put your address onto the bridge. You will then have one network, and the bridge software will pass packets between them, as well as keeping track of which clients are in which network segment.

As far as (almost) all software on your box is concerned, you just deal with one interface (the bridge, eg br0). What I am unsure about is how dhcpd behaves in this case - hopefully someone who's run this setup can comment ? I would hope that it would use the bridge interface in the same manner as it would use a "real" one, but there can be some subtle differences.

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