On 3/28/25 18:33, support | IT visibility wrote:
On 3/24/25 09:47, support | IT visibility via Dnsmasq-discuss wrote:
Hi *,
I’m using dnsmasq with a few vlan interfaces and each interface is tagged.
And running tests with pihole as well as native dnsmasq.
An example on how this is setup in both cases (.i.e. pihole as well as
native dnsmsaq):
=====
# Wired - vlan 210
interface=eth0.210
domain=wired.lan,192.168.210.0/24,local
dhcp-range=set:vlan-210,192.168.210.11,192.168.210.99,168h
dhcp-option=tag:vlan-210,option:router,192.168.210.241
dhcp-option=tag:vlan-210,option:dns-server,192.168.210.235
dhcp-option=tag:vlan-210,option:ntp-server,192.168.210.235
dhcp-option=tag:vlan-210,option:domain-name,wired.lan
=====
The idea behind this is that devices with multiple vlan interfaces
have their IP’s registered with dhcp and dns.
The dhcp part seems to work – all interfaces have the correct IP details.
However, the log has numerous wrong-address errors like this (i.e.
pihole as well as native dnsmasq):
=====
Mar 24 09:02:03 dnsmasq-dhcp[49]: DHCPREQUEST(eth0.210)
192.168.210.201
bc:24:11:87:be:e5
Mar 24 09:02:03 dnsmasq-dhcp[49]: DHCPNAK(eth0.210) 192.168.210.201
bc:24:11:87:be:e5 wrong address
Mar 24 09:02:03 dnsmasq-dhcp[49]: DHCPDISCOVER(eth0.210)
bc:24:11:87:be:e5
Mar 24 09:02:03 dnsmasq-dhcp[49]: DHCPOFFER(eth0.210) 192.168.210.201
bc:24:11:87:be:e5
Mar 24 09:02:03 dnsmasq-dhcp[49]: DHCPREQUEST(eth0.210)
192.168.210.201
bc:24:11:87:be:e5
Mar 24 09:02:03 dnsmasq-dhcp[49]: DHCPACK(eth0.210) 192.168.210.201
bc:24:11:87:be:e5 osiris
=====
*Question-1*: where are these wrong-address messages coming from?
If I look at the dhcp.leases (Pihole) or dnsmasq.leases (native
dnsmasq) there is always one entry like this:
1743408124 bc:24:11:87:be:e5 192.168.230.201 osiris *
*Question-2*: why is there only an entry from the last vlan interface
of (in this example) osiris? And not one for every vlan interface?
*Question-3*: the same applies for dns regestrations where there is
only an entry for the last vlan interface?
I have tried to force this dns regestration for all fqdn’s for each
vlan using the following settings (i.e. pihole as well as native dnsmasq):
dhcp-ignore-clid
dhcp-fqdn
dhcp-client-update
expand-hosts
domain-needed
domain=lan
local=/lan/
Does the above ring any bells? Any suggestion?
With warm regards – Will
Answer 1: Because a lease exists for the relevant MAC address with a different
IP address to the address it's requesting.
Answer 2: Because the device is using the same MAC address on all the VLANS
it's talking through. The MAC address is supposed to be unique: a DHCP
server won't allow a MAC address to have more than one lease.
Answer 3: Partly the same answer as 2, but even if you use unique MAC addresses
(or client-ids) dnsmasq will only associate a DNS name with at most one
DHCP lease. That's a design decision.
=====
Thank you for the detailed and to-the-point answers... which makes me wundering:
If the mac-address is unique and clid is set via the duid option, all
interfaces/vlan-domains are registered in DNS.
In addition, the leases file shows all the registrations - including the clid
for each interface.
This showed me that both are unique across all interfaces.
If I then remove the custom mac addresses (leaving the unique clid's in place),
only the last one is registered in dns.
Which is not what I would expect based on what the manual says about the way
things are expected to work with clid's.
This was tested with a Debian LXC-container where I replaced ifupdown and
isc-dhcp-client with systemd-networkd.
What am I missing/overlooking here?
Do you still have dhcp-ignore-clid in your configuration? That would
mess what you're trying to do here.
Cheers,
Simon.
With warm regards - Will
=====
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