[Dnsmasq-discuss] client q: both static and dhcp

Geert Stappers stappers at stappers.nl
Sun Jun 27 07:44:15 UTC 2021

> These machines are portable.


On Sun, Jun 27, 2021 at 01:26:24AM -0500, Carl Karsten wrote:
> On Sun, Jun 27, 2021 at 12:03 AM Dominik <dl6er at dl6er.de> wrote:
> > Hey Carl,
> >
> > On Sat, 2021-06-26 at 19:16 -0500, Carl Karsten wrote:
> > > I'm looking for advice on haveing some boxes to have both dynamic and
> > > static IPs.
> >
> > Why use a static IP at all? We have often enough seen people use static
> > addresses for the wrong reasons.
> >
> > Consider using only DHCP and
> >
> > (a) use a hostname to access the device. In the end, memorizing some-
> > service.lan is more reliable than You may think
> > differently, but let's see what you say after not having logged into
> > the box for half a year - do you still know the address without looking
> > it up? However, you may still recall a good hostname.
> >
> > (b) use a deterministic DHCP server like dnsmasq. It always tries to
> > assign the same IP addresses to the same devices (instead of numbering
> > them sequentially based on their appearance like cheap routers often
> > do).
> >
> > Using (a), (b) or (a)+(b) doesn't require you to have a static IP at
> > all.
> >
> These machines are portable. they will likely start out on a lan where I
> control the dhcp server;  the os apps and config are setup, then they are
> moved to another room.   They live there for a few days to a week, and then
> are put back in storage, with a few being left out for R&D to experiment
> with.
> There isn't always a dhcp server on the network.

There is the true problem.

And that problem implies manual assignment of IPv4 addresses
plus setting router and most likely DNS  (or even worse: At N servers
updating N entries in /etc/hosts)

> Sometimes there isn't even a network with the exception of a single
> run of cat 5 between 2 machines.
> This is what is going on:
> https://debconf-video-team.pages.debian.net/docs/room_setup.html#room-setup
> Sometimes there isn't a link to "DHCP – Gigabit feed out" (thus there is no
> live stream, just recording to local disk)
> This is what I want the static IP for:
> The "Opsis PC" has a systemd script that connects to "Voctomix PC"
> The script uses a hostname, the hostname is set in /etc/hosts
> If there is a network with dhcp, then it will be nice to get the gateway
> and be able to ssh into machines.

I recommend to add an OpenWRT device or another portable DHCP server + DNServer
to the equipment.

> > Best,
> > Dominik
> >
> Carl K

Geert Stappers

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