I’m running Linux Mint on a home server that happens to run pihole. Since it’s both a dhcp and dns server for my network, it has a static ip address. It has an ethernet connection as well as wifi and it’s always been my understanding that you can’t have two network interfaces sharing the same IP address, so I’ve been looking into ways to have one network adapter enabled and the other disabled and then if the network connection of the active device is lost, the other re-enables with the same IP address and disables the other device. This mostly work.
However while debugging one bit of software that seems to have a problem with me disabling my wifi adapter, I inadvertently enabled both the eth and wifi connections while each have the same, manually assigned ip address and everything so far just seems to work. I didn’t think this was possible and I’m wondering, should I expect problems? I can connect to the machine remotely fine, pihole and dvr services installed on the box work. Is there any reason to believe this won’t work?
There is no DHCP, it’s all static addresses, but there is an ARP table maintained at the router, and modern routers protect against ARP poisoning, meaning the same IP cannot have two mac addresses, and they will churn out errors. It’s also a security nightmare because many low level packet tracing tools will not work or give out false positives. I still don’t know how it’s working for you, because by all accounts, it shouldn’t.
Metric seems to cause Linux to mostly arp reply on one interface. Not a lot of switching. I can even plug in an Ethernet cable during a network transfer to speed it up.
Linux treats ips as assigned to the host,so any interface can respond for packets sent to another interface (even if they have different ip addresses).
There is some network weirdness that a security scanner might complain about, but it “works”.