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pythonlinuxipmac-addressarp

Python: get MAC address of default gateway

Is there any quick way in Python to get the MAC address of the default gateway?

I can't make any ARP requests from the Linux machine I'm running my code on, so it has to come directly from the ARP table.

Solution

  • The following DevFS files will provide this information:

    /proc/net/arp
/proc/net/route

    Find the route entry with 0/0 as the host/mask:

    Iface   Destination     Gateway         Flags   RefCnt  Use     Metric  Mask            MTU     Window  IRTT                                                       
eth0    00000000        B91A210A        0003    0       0       100     00000000        0       0       0

    and convert the Gateway field (it's in little-endian hex... grr):

    import struct
from IPy import IP
address = IP(struct.unpack('<I', struct.pack('>I', int(i, 16)))[0])
#Converts 'B91A210A' to IP('10.33.26.185')

    From there, you can find your default gateway in the arp table:

    IP address       HW type     Flags       HW address            Mask     Device
10.33.26.185     0x1         0x2         e6:92:ec:f5:af:f7     *        eth0

    If it doesn't show up, issue a single ping, then check again, then fail.