I have a new laptop on my network which requires a USB->Ethernet dongle for a wired connection. I assigned different static leases to the laptop wifi and the dongle.
The wifi device gets it's static lease correctly, but the dongle ONLY ever gets a dynamic address from the DHCP pool. The system log is full of:
Mon Mar 23 14:40:02 2026 daemon.info dnsmasq-dhcp[1]: DHCPDISCOVER(br-lan) 10.1.100.127 30:23:03:e2:06:b1
Mon Mar 23 14:40:02 2026 daemon.info dnsmasq-dhcp[1]: DHCPOFFER(br-lan) 10.1.100.10 30:23:03:e2:06:b1ode here
(10.1.100.30 is the assigned static - 10.1.100.127 is from the DHCP pool).
I've tried a broad variety of cleanups directly on the router, re-starting the router and the laptop, etc.
Is this a problem with the device or do I need to do additional configuration?
Make sure the lease reservation MAC is using colons instead of dashes. dnsmasq won’t recognize dashes in a MAC, and therefore would appear to ignore the reservation.
Laptop is dual-boot, Windows and Ubuntu. The dongle has a windows app that sets up something called "pass-through" - when I do that, the DHCP server sees the wifi MAC and correctly assigns that static lease. Without setting the pass-through mode on Windows, or when booting Ubuntu, the DHCP server sees the MAC for the dongle, and FAILS to assign the correct static lease
A pre-existing dynamic DHCP lease in dnsmasq's state files takes precedence over static reservation, because it's still an active lease and can't just be pulled (rebooting the router, among other approaches, does fix that).
Given your explanation (which involves rebooting the router), that shouldn't be your issue though.
Errors in the dnsmasq configuration (wrong pool size for the start value, pool overlapping with the router's own IP, things like that) can cause similar behaviour though.
Possible, some computers bind the chassis MAC to connected (USB-) ethernet cards. Kind of makes sense for a notebook in a dock (not really, if you think about it deeper). in that case there may be BIOS settings about it (and there might be interesting behaviour while the driver initializes).
This particular laptop (Lenovo X1 Carbon Gen 11) DOES have a BIOS setting entitled "MAC Address pass-thru", and according to the help, this should "bind the dock to the chassis MAC address". However, when I set it, the static lease that I set for the dongle is correctly assigned on boot. Which makes no sense to me
Even weirder ... if I boot into Windows, the pass-thru "works" and I see the wifi MAC on the ethernet dongle, but in Ubuntu, I see the wifi MAC on the wifi connection and the MAC for the dongle on the wired connection!!
IP addresses can also be reserved by hostname. As long as you can set a hostname that is unique on your network, the same address will be assigned to any MAC used by that host.
