IP stops broadcasting when sshed to.

[Scott Cohen]

When I do a scan of my local network via the command arp-scan --localnet, I find that the IP of the machine which has Ubuntu-MATE on it shows up in the list of IPs brought back by arp-scan. But when I ssh to that machine and then issue the command arp-scan --localnet from the machine that I had sshed from, I find that the IP address of the computer with Ubuntu-MATE on it is absent from the list. I'm not sure what information I can give other than my list of installed packages and that I'm running Ubuntu-MATE 17.10 getting updates from the developer repository.

I posted a bug report here: https://bugs.launchpad.net/ubuntu/+source/network-manager/+bug/1711465
This has more thorough data if applicable.

[nadrimajstor (ipejic)]

AFAIK, As arp-scan will show data for packets that went trough the interface, you won't see ARP request/reply to itself (as those will not "reach the wire"). Hence, the "missing" local IP/MAC pair.
IINM, You can observe same behavior on any other linux system and with other tools (netdiscover, tcpdump).
(I agree that this behavior does make additional cognitive load - It will easily show duplicate IP address for other hosts but for your own host you have to keep in mind that your IP/MAC is missing from the report)

[Scott Cohen (yetoo)]

So, if I understand correctly, this an issue with the arp-scan package?

[nadrimajstor (ipejic)]

I believe so.
If my understanding on how tools that relay on libpcap works (arp-scan, netdiscover, ...) this could be a feature request for them.
For example, netdiscover beside active mode (that arp-scan also use) it have an additional passive mode, where it does not send ARP requests just listen for other's and it also omits local IP/MAC from report.