Hi, this is Sandra Henry-Stocker, author of the “Unix as a Second Language” blog on NetworkWorld.
In this Linux tip, we’re going to look at the ip neigh command. It works a lot like the arp command, but is considerably newer and still in active development. It provides network details – IP and MAC addresses — along with an indication of each system’s accessibility, but only for systems on your local network.
Here’s an example:
Most of this information is straightforward. It shows the IP addresses on the left, the network interface on the system you’re connecting from (3rd field), the hardware address of the remote system following the term “lladdr” (link level address) and the connection status. STALE entries are valid but suggest there haven’t been any connections in a while.
PERMANENT – manually added to the arp table as a static entry
REACHABLE – connected recently
DELAY – no recent verification received
STALE – no verification for 30 seconds or more
INCOMPLETE – address resolution in progress
In case you’re curious, the first three bytes of each hardware address (e.g., f8:8e:85) indicates the device’s manufacturer. This one (3rd in the list above) is a Comtrend router.
NOTE: The system this command is run on isn’t included in the output because it’s not needed in the arp table used to connect to other systems.
That’s your Linux tip for the ip neigh command.
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