FTL Two MACs to One IP/Hostname?

Greetings. I've read posts that come near to answering this question, but not quite.

I'd like to map two (or more?) MACs to the same IP address and hostname. In my case, it's because I have two NICs in my (Linux) laptop, and I want to treat the laptop as the same machine regardless of which NIC is in use. Right now I've got NIC 1 (eth) set to DHCP assigned via FTL (5.7) in Pi-hole, with NIC 2 (usb) configured with a static IP at the laptop. That's a workaround, but it seems less than ideal.

The Pi-hole web interface blocks an attempt to create a duplicate lease, and hand-editing 04-pihole-static-dhpc.conf proved to be ... a bad decision. I don't want to blow up my system again, so I'm wondering if there's a way to implement (outside the interface):


I found the above in a dnsmasq discussion, with the claim that dnsmasq will release a valid, unexpired, in-use lease using this syntax in its configuration file.

Any help appreciated,


Assigning the same IP address to two different MACs at the same time is a really bad idea.
It will severly mess up routing. If packages are routed to your NIC at all, an application may wait forever for an answer to a request that went out through NIC1, but arrived at NIC2, where your OS driver will just discard it as it doesn't know an associated request. Or your router may invalidate one of the MACs, not accepting packets from or delivering packets to it anymore.

It could only ever be an option if you can guarantee those two NICs will NEVER be active in your network at the same time, and only if those devices are strictly IPv4 only. Even then, your router may not play along nicely, especially if its routing table still holds entries for the respective other MAC address with the same IP.

For IPv6, your machine will continue to happily assign the usual set of IPv6 addresses (one link-local, zero or more ULAs, zero or more GUAs) to each of your interfaces.

As far as DNS is concerned, associating a hostname with several IP addresses is certainly possible.
Still, defining the respective records may mean a hit to responsiveness while a client works through the list of IPs until the active IP is found. Less intelligent programs may just use the first IP and fail if that's not available.

I'd strongly recommend to use two separate IPv4s and two separate hostnames for your two separate network interfaces. You can align IPs and use similar hostnames to help you identify it's the same laptop (e.g. laptop-wifi and laptop-eth).