Alex Ruben
How To Find All MAC Addresses and Their Corresponding IPs in Your Local Network (LAN) on Linux
Finding out what’s actually connected to your LAN can be a bit of a headache, especially if you’re paranoid about unknown devices lurking around. Sometimes, the standard tools just don’t show everything, or maybe you just want a quick overview. This guide is about getting an accurate list of all devices on your local network—showing their MAC and IP addresses—so you can keep tabs or troubleshoot issues. We’ll mostly use arp-scan because it’s pretty solid at crawling your network, plus a fallback with ip neigh. By the end, you’ll have a pretty good grip on what’s connected without needing any fancy network monitoring setup.
Prerequisites
Before diving in, make sure you’ve got:
- An Ubuntu machine (the commands might need tweaks for other distros, but most are similar).
- Terminal access with sudo rights—unless you wanna do everything as root, which is not recommended.
- Internet connection to grab the tools you’ll need.
How to Find Everything on Your Network: The Practical Ways
Install arp-scan — your main weapon for network discovery
This tool is kinda the bread and butter for scanning local subnets. If it’s not installed yet, you’ll have to add it first. Here’s why it helps: arp-scan actively probes your network, asking every device “Hey, who’s there?” and then reports back. It’s reliable, fast, and usually catches even those sneaky devices not listed in your DHCP lease. When it works, expect a clean list of MAC/IP combos of pretty much everything connected.
- Open Terminal.
- Type or copy-paste:
sudo apt update && sudo apt install arp-scan
Note: Sometimes, on Windows or Mac, you’d use different tools, but here, it’s all Linux-native magic.
Scan your network with arp-scan — see what’s really out there
Running arp-scan on your main network interface usually reveals all devices. But first, figure out what your network interface actually is. Run:
ip addr
This will list all network interfaces with their IPs. Look for something like eth0 or wlan0. Once identified, perform the scan:
sudo arp-scan --interface=wlan0 --localnet
If you don’t specify –interface, it defaults to the primary one, but setting it explicitly can sometimes help. This command sends out ARP requests across your subnet and gathers responses. The output should show each device’s MAC and IP, like a little dossier on your network “friends.”
On some setups, the scan might not show everything the first time—maybe due to network isolation or device firewalls. Just rerun if needed. Also, ensure your network isn’t on some managed VLAN or guest network that blocks ARP traffic.
Use ip neigh — a quick peek at the ARP cache
If you want a lightweight, instant look without the hassle of scanning, ip neigh is handy. It just checks your local ARP table, which is kinda like the phonebook your OS keeps. The catch is, it only shows currently known devices, so if something just connected or disconnected, it doesn’t update in real time. Still, for quick checks, it’s solid.
- Type:
ip neigh
This will spit out a list of IP addresses paired with Mac addresses, like:
192.168.1.10 dev wlan0 lladdr 00:11:22:33:44:55 REACHABLE 10.0.0.5 dev eth0 lladdr aa:bb:cc:dd:ee:ff STALE
It’s not exhaustive, but handy for quick verification, especially if you’ve recently connected something.
Extra tips & what might throw these off
- Make sure your network card or Wi-Fi is fully active—no quiet mode or disabled interfaces.
- Run these scans when nobody’s streaming or downloading heavily, because network congestion can cause weird delays or missed responses.
- If arp-scan or ip neigh gives incomplete info, try disabling VPNs or virtual adapters—they can mess with network visibility.
- Sometimes, permissions bite you: always prepend sudo for these commands, or you might just see blank outputs.
Wrap-up
Getting a handle on who’s on your LAN isn’t rocket science, but it does take a bit of fiddling around with the right tools. arp-scan is usually the most reliable for discovering connected devices, and ip neigh is good for a quick look at what your system already knows about. Just keep in mind, network configurations or device firewalls can hide or block some info, so sometimes, the list isn’t perfect. Experimenting with both methods usually covers most scenarios.
Frequently Asked Questions
What’s the main difference between arp-scan and ip neigh?
arp-scan really probes the network by asking everyone directly, so it finds stuff that might’ve not yet popped up in your ARP cache. ip neigh just looks at what’s already been seen—kind of like peeking into the OS’s recent call list. If you want fresh info, arp-scan wins; for speed, ip neigh is faster but less complete.
Can I run these commands on other Linux distros?
On most Linux systems like Fedora, Arch, or Manjaro, arp-scan and ip are available via their package managers. Just install arp-scan with your distro’s package tool and everything should work.
What if I can’t see all devices I know are connected?
Check network interface settings, or make sure your device isn’t on a separate subnet or VLAN. Firewalls and network isolation can also block ARP traffic, so sometimes it’s not your tools—just network policy.
Summary
- Use sudo apt install arp-scan if you haven’t already.
- Identify your interface with
ip addr. - Run
sudo arp-scan --localnetto discover devices. - Check your ARP cache with
ip neighfor quick info. - Make sure your network isn’t blocking ARP requests or responses.
Final thoughts
Figuring this stuff out isn’t always straightforward—networks can be weird, devices can hide, and sometimes you’re just chasing ghosts. Still, these methods cover most scenarios. On one machine it might be a breeze, on another… not so much. But at least you’ll have a few tricks to get the job done. Fingers crossed this helps someone save time or catch that rogue device that shouldn’t be there.