arp
Networking
Usage
arp -aShows the table of MAC addresses for neighbours on the same local network; anything beyond the router is never in it, and on Linux `ip neigh` is the current tool.
Common flags
| Flag | Meaning |
|---|---|
| -a | The whole neighbour cache, name plus MAC address. |
| -n | Numeric only, no name lookups. |
| -d <host> | Delete one entry, which forces a fresh lookup. |
| -s <ip> <mac> | Add a static entry by hand. |
Examples
arp -aThe MAC addresses of machines on this network segment.
sudo arp -d 192.168.1.10Clear a stale entry after a device changed hardware.
When a connection fails, these narrow down how far it got — name not resolving, no route, or a blocked port.
How to read this
- Square brackets [ ] mark a part you may leave out.
- An ellipsis … means you can list more than one.
- Flags are case-sensitive — in some commands -r and -R do different things.
Questions
Q. What does arp do?
Shows the table of MAC addresses for neighbours on the same local network; anything beyond the router is never in it, and on Linux `ip neigh` is the current tool.
Q. How do I type it?
arp -a — square brackets mark the parts you can leave out.
Q. How many flags are worth knowing?
4 are listed here; the full set is in man arp. This command sits under Networking.
Related commands
man page: man arp