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 arping command. If it sounds like a combination of arp and ping, that should serve as a hint for how it works. It’s a command that you can use to discover or probe systems on your local network. For example, on the common 192.168.0.0 network, your default router is normally 192.168.0.1. We can use arping like this:
In this example, we see the request is going from 192.168.0.11 (our local system) to the router (192.168.0.1) through enp0s25 (the default ethernet port).
The -c 2 shows we’re going to send two requests for the system to respond. Notice that we get two responses back. We also see the hardware (MAC) address for the router displayed and the time that it took to receive each of the replies to be returned.
The first three bytes of the MAC address (F8:8E:85) also indicates the manufacturer of the router that we’re probing. In this case, it’s a Comtrend router.
Note that the arping command cannot send requests to systems outside of your local network because it works at the MAC level and is therefore non-routable. For this very reason, however, it can be especially useful for finding hosts that might not respond to layer 3 and layer 4 ping requests. So, it can come in very handy.
That’s your Linux tip for arping.
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