help on assigning invalid IP addresses

[Leonardo Boselli]

subnet with some server (fixed public IP addresses), workstation
(same, assigned by dhcp), portable (dhcp dynamic), peripherals using only
link local fe80:: IPv6
addresses.
All was fine until arrived a couple of peripherals that get their IPv4
address via dhcp and there is no way to avoid them to get it, even if you
access then only via IPv6 .
I have added in the imcluded file that assign always the same address to
workstations based on mac addresses record as

host XRX0000AABBCCDD {
hardware ethernet 00:00:aa:bb:cc:dd;
fixed-address 10.240.13.112;
option routers 10.240.13.1;
option subnet-mask 255.255.255.0;
}

but the resut is that while addresse in the "real" subnet assigned to
workstations works fine an are correctly assigned, peripherals insist on
getting public addresses from the pool of portables, that is something i
do not want.
How can i assign completely invalid (or better, unrouted) IPv4 addresses ?

--
Leonardo Boselli
DICEA
tel +39 0552758808 +39 3488605348

[Chris Bell]

Try using the package dnsmasq either on your firewall or a static server to
give a combination of static and dynamic address allocations over multiple
local networks.

--
Chris Bell
Website http://chrisbell.org.uk

[Emil Pedersen]

--On 17 januari 2020 16:06:20 +0100 Leonardo Boselli <l...@dicea.unifi.it>
wrote:

Just to check, do you have a specification for the "invalid" subnet in some
way in the dhcp server pointing in the same direction as the "good" subnet?

It was quite a long time since I messed with dhcp so I may be wrong but I
think that is required for what you want. Like setting an extra (invalid)
address on the same interface and maybe a shared network wrapping with both
of the networks in the dhcp config (no available addresses for the bad one
except the one fixed to the device).

// Emil

[Leonardo Boselli]

On Fri, 17 Jan 2020, Emil Pedersen wrote:
> Just to check, do you have a specification for the "invalid" subnet in some
> way in the dhcp server pointing in the same direction as the "good" subnet?

I have

subnet 10.240.13.0 netmask 255.255.255.0 {
}

and the dns server has 10.240.13.3/24 assigned ....

> It was quite a long time since I messed with dhcp so I may be wrong but I
> think that is required for what you want. Like setting an extra (invalid)
> address on the same interface and maybe a shared network wrapping with both
> of the networks in the dhcp config (no available addresses for the bad one
> except the one fixed to the device).

bit question is: if i give addresses, even just one, in the "invalid"
network how can I be sure that are not assigned to regular clients ?


--
Leonardo Boselli
DICeA

[Leonardo Boselli]

On Fri, 17 Jan 2020, Leonardo Boselli wrote:

> subnet 10.240.13.0 netmask 255.255.255.0 {
> }

including not an empty declaration but a full declaration (just without
range) did work .

--
Leonardo Boselli
Dipartimento Ingegneria Civile e Ambientale UNIFI