I definitely don’t intend to run anything core over wifi… my home servers all have direct eth connections but also have WiFi hardware that came with them. The WiFi is really just a backup in case the switch they’re connected to dies. And since it turns out the eth and WiFi devices can share the same ip, having a resilient backup was easier than I expected.

In terms of size, the networks has about 70 devices and I’ve got 2 pi hole servers running dhcp & dns services, including unbound, all with ups’ and a generator backup so it’s about as resilient as I can make it.

Thank you for the link… I didn’t know that was a thing. In the mean time though I can’t find a problem with what I’ve got… 2 connections with the same IP.

I simply wanted a fail-over but in the process got 2 interfaces with the same IP and I can’t find a problem with it 😄

What won’t work, because at the moment everything seems to be working fine and I’m pleasantly surprised.

In terms of why, all I really want is for the machine to have the same, consistent ip address. Since it’s one of my networks dns and dhcp servers, I want it always available with the same ip. It’s hard-wired but has wifi, so in theory if the eth connection or switch it’s attached to dies, the wifi connection can kick in and it can still serve the network if it still has the same ip address, otherwise the wifi connection is no benefit.

Since I didn’t know I could assign both connections the same ip address and still be functional, I originally setup a script that monitors network status and disables the wifi if eth is active and then re-enables the wifi if the eth connection drops. This works well on my two servers with one exception… my dvr scheduling/recording services don’t work properly when the wifi adapter is disabled. Not sure why but that’s how I stumbled on this setup with both active with the same ip and realized everything just seemed to work.¯\_(ツ)_/¯

That’s the thing about UDP packets… receipt isn’t acknowledged as part of the protocol. It’s send and forget. I’m not sure a UDP packet sent to my server would get lost but I’m not 100% certain there couldn’t be situations where the packet is received by the server on both interfaces, essentially duplicated. It’s been almost 30 years since I wrote programs that utilized UDP for communicating. I’m definitely a little rusty. 😄

Will UDP packets produce an error when sent or will they simply be received twice, potentially causing errors/issues?

You will need to make sure the IP you assign the adapter isn’t an IP the router will try to assign to another machine or device. The dhcp services don’t assign this IP address and it’s manually assigned in the adapter config so I guess the router doesn’t know or care.

I am kind of curious how traffic destined for this address doesn’t have issues though, like being received twice. Maybe I haven’t tested enough from a mix of devices on the network.

I know I’m a heretic but I’m a huge powershell fan. Once you work with an object-oriented shell you’ll wonder why you’ve dealt with parsing text for so long. Works great on Linux, MacOS and Windows, it’s open source, reads and writes csv, json and xml natively, native web and rest service support, built-in support for remote computing and parallel processing and extensive libraries for just about anything you can think of. It takes a little getting used to but it’s worth it.