I would like to display the output table of the arp
command every 30 seconds, so that I can monitor Address Resolution Protocol traffic on my network.
Unfortunately arp
doesn't have such option. It only prints the current content of the table once, like this:
Address HWtype HWaddress Flags Mask Iface
192.168.0.103 ether 48:e2:44:d5:7a:97 C eth0
192.168.0.1 ether c8:3a:35:49:77:48 C eth0
So I usually end up running arp
several times manually to detect any changes in the table entries, which is not very sophisticated.
In order to automate this task, I read that the watch
command allows to repeat commands automatically (1, 2, 3). Therefore I prepended watch -n 30
to arp
like this:
watch -n 30 arp
However, when I run it I don't get any kind of output. The table is not even printed once.
Why is that? How can I solve this?
This answer shows a working example with nmcli dev
, so I see no reason why this should not be possible to do with arp
.
I am using Xubuntu 16.04 Xenial Xerus.