Obtain MAC Address from Devices using Python

Question

I'm looking for a way (with python) to obtain the layer II address from a device on my local network. Layer III addresses are known.

The goal is to build a script that will poll a databases of IP addresses on regular intervals ensuring that the mac addresses have not changed and if they have, email alerts to myself.

Answer 1

an easier way, if on linux:

print os.system('arp -n ' + str(remoteIP))

you will get:

    Address        HWtype  HWaddress           Flags Mask            Iface
    192.168.....   ether   9B:39:15:f2:45:51   C                     wlan0

Answer 2

Try using the netifaces found here. netifaces

Answer 3

for Unix based systems:

#!/usr/bin/env python2.7

import re
import subprocess
arp_out =subprocess.check_output(['arp','-lan'])

re.findall(r"((\w{2,2}\:{0,1}){6})",arp_out)

will return list of tuples with macs. scapy is an amazing tool , but seems to be overkill for this case

Answer 4

There was a similar question answered not too long ago on this site. As mentioned in the answer chosen by the asker of that question, Python doesn't have a built-in way to do it. You must either call a system command such as arp to get ARP information, or generate your own packets using Scapy.

Edit: An example using Scapy from their website:

Here is another tool that will constantly monitor all interfaces on a machine and print all ARP request it sees, even on 802.11 frames from a Wi-Fi card in monitor mode. Note the store=0 parameter to sniff() to avoid storing all packets in memory for nothing.

#! /usr/bin/env python
from scapy import *

def arp_monitor_callback(pkt):
    if ARP in pkt and pkt[ARP].op in (1,2): #who-has or is-at
        return pkt.sprintf("%ARP.hwsrc% %ARP.psrc%")

sniff(prn=arp_monitor_callback, filter="arp", store=0)

Not exactly what you're looking for, but definitely on the right track. Enjoy!

Answer 5

To answer the question with Python depends on your platform. I don't have Windows handy, so the following solution works on the Linux box I wrote it on. A small change to the regular expression will make it work in OS X.

First, you must ping the target. That will place the target -- as long as it's within your netmask, which it sounds like in this situation it will be -- in your system's ARP cache. Observe:

13:40 jsmith@undertow% ping 97.107.138.15
PING 97.107.138.15 (97.107.138.15) 56(84) bytes of data.
64 bytes from 97.107.138.15: icmp_seq=1 ttl=64 time=1.25 ms
^C

13:40 jsmith@undertow% arp -n 97.107.138.15
Address                  HWtype  HWaddress           Flags Mask            Iface
97.107.138.15            ether   fe:fd:61:6b:8a:0f   C                     eth0

Knowing that, you do a little subprocess magic -- otherwise you're writing ARP cache checking code yourself, and you don't want to do that:

>>> from subprocess import Popen, PIPE
>>> import re
>>> IP = "1.2.3.4"

>>> # do_ping(IP)
>>> # The time between ping and arp check must be small, as ARP may not cache long

>>> pid = Popen(["arp", "-n", IP], stdout=PIPE)
>>> s = pid.communicate()[0]
>>> mac = re.search(r"(([a-f\d]{1,2}\:){5}[a-f\d]{1,2})", s).groups()[0]
>>> mac
"fe:fd:61:6b:8a:0f"

Answer 6

In Linux sometimems you miss the command line util "arp". A base yocto linux embedded environment image for instance.

An alternative way without the "arp" tool would be to read and parse the file /proc/net/arp:

root@raspberrypi:~# cat /proc/net/arp
IP address       HW type     Flags       HW address            Mask     Device
192.168.1.1      0x1         0x2         xx:xx:xx:xx:xx:xx     *        wlan0
192.168.1.33     0x1         0x2         yy:yy:yy:yy:yy:yy     *        wlan0