30
Can a server's eth & wifi share the same IP address?
(lemmy.world)
you are viewing a single comment's thread
view the rest of the comments
view the rest of the comments
this post was submitted on 04 Jun 2026
30 points (100.0% liked)
Linux
65497 readers
410 users here now
From Wikipedia, the free encyclopedia
Linux is a family of open source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991 by Linus Torvalds. Linux is typically packaged in a Linux distribution (or distro for short).
Distributions include the Linux kernel and supporting system software and libraries, many of which are provided by the GNU Project. Many Linux distributions use the word "Linux" in their name, but the Free Software Foundation uses the name GNU/Linux to emphasize the importance of GNU software, causing some controversy.
Rules
- Posts must be relevant to operating systems running the Linux kernel. GNU/Linux or otherwise.
- No misinformation
- No NSFW content
- No hate speech, bigotry, etc
Related Communities
Community icon by Alpár-Etele Méder, licensed under CC BY 3.0
founded 7 years ago
MODERATORS
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'm at a loss as to how this would work consistently. If 2 interfaces share an IP without bonding, then only 1 would answer the ARP request from anothet host trying to establish a connection. If your system allows same static on 2 devices on same land, then other hosts talk to whoever establishes a session or answers the ARP request.
I'm curious why you would want this at all?
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)_/¯
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".