How to get the MAC address of the 'local' system given the IP address?

[rikona]

On Thu, 30 Jan 2020 17:22:48 +0000
Chris Green <cl at isbd.net> wrote:

> You'd think this was easy but although I can find the information
> easily enough I can't find a concise way of doing it.

Perhaps you might log onto the router? Mine gives me a table with the
IP and MAC addresses for all connected devices.

Rik

> What I want is to get same information for the system I'm logged into
> as is given by 'arp-scan -lx' for all other systems on the LAN:-
> 
>     root at t470:~# arp-scan -lx
>     192.168.1.1     xx:xx:xx:xx:xx:xx       DrayTek Corp.
>     192.168.1.3     xx:xx:xx:xx:xx:xx       Fujitsu Technology
> Solutions GmbH 192.168.1.4     xx:xx:xx:xx:xx:xx       Raspberry Pi
> Foundation 192.168.1.10    xx:xx:xx:xx:xx:xx       TP-LINK
> TECHNOLOGIES CO.,LTD. 192.168.1.20    xx:xx:xx:xx:xx:xx       DrayTek
> Corp. 192.168.1.50    xx:xx:xx:xx:xx:xx       Oki Electric Industry
> Co., Ltd. 192.168.1.96    xx:xx:xx:xx:xx:xx       HUMAX Co., Ltd.
>     192.168.1.98    xx:xx:xx:xx:xx:xx       TP-LINK TECHNOLOGIES
> CO.,LTD. 192.168.1.111   xx:xx:xx:xx:xx:xx       TP-LINK TECHNOLOGIES
> CO.,LTD. 192.168.1.114   xx:xx:xx:xx:xx:xx       MICRO-STAR INT'L
> CO.,LTD 192.168.1.95    xx:xx:xx:xx:xx:xx       Sonos, Inc.
>     192.168.1.104   xx:xx:xx:xx:xx:xx       Amazon Technologies Inc.
> 
> I can get IP address of my current LAN connection using 'hostname
> -i':-
> 
>     chris$ hostname -i
>     192.168.1.92
> 
> ... but I can't find a neat way of getting the corresponding MAC
> address and company information as for arp-scan. The MAC address can
> be obtained using ifconfig or ip but it's an exercise in frustration
> trying to extract the relevant bits:-
> 
>     chris$ ifconfig
>     enp0s31f6: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
>             ether c8:5b:76:de:2a:fc  txqueuelen 1000  (Ethernet)
>             RX packets 0  bytes 0 (0.0 B)
>             RX errors 0  dropped 0  overruns 0  frame 0
>             TX packets 0  bytes 0 (0.0 B)
>             TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
>             device interrupt 16  memory 0xec200000-ec220000
> 
>     lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
>             inet 127.0.0.1  netmask 255.0.0.0
>             inet6 ::1  prefixlen 128  scopeid 0x10<host>
>             loop  txqueuelen 1000  (Local Loopback)
>             RX packets 639  bytes 279749 (279.7 KB)
>             RX errors 0  dropped 0  overruns 0  frame 0
>             TX packets 639  bytes 279749 (279.7 KB)
>             TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
> 
>     wlp4s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
>             inet 192.168.1.92  netmask 255.255.255.0  broadcast
> 192.168.1.255 inet6 fe80::8239:9067:e11:92be  prefixlen 64  scopeid
> 0x20<link> ether xx:xx:xx:xx:xx:xx  txqueuelen 1000  (Ethernet)
>             RX packets 14315  bytes 7281010 (7.2 MB)
>             RX errors 0  dropped 1  overruns 0  frame 0
>             TX packets 14719  bytes 1911802 (1.9 MB)
>             TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
> 
> 
> You'd have to first find that the WiFi device wlp4s0 is providing the
> LAN interface (I want it to work when it's wired with enp0s31f6 when
> that's in use, can't just hard code wlp4s0) and then go to the 'ether'
> line to get the MAC address.  Even then you don't get the company
> name. It's possible but hard work and messy, I'd like to find a
> simple way.
>