Getting Ip Address

[flamel]

Hi Monks,

I need to discover the ip address of a remote network device in my internal network(I know his Mac Address).
Is there a way do that in perl?

Thanks in Advance.

[Joost]

this link says that you can't do this generally, but that you can get the mac address from visited IPs in the arp cache.

Depending on your OS, you can get at that information in different ways. My linux box seems to store the IP/MAC info in /proc/net/arp, for instance. I have only one machine running here at the moment so it only shows my own address:

IP address       HW type     Flags       HW address            Mask   
+  Device
192.168.2.1      0x1         0x2         00:13:F7:27:FB:8A     *      
+  eth0

I suppose that you could ping all the IP addresses in your local subnet and then check the arp cache for matching MAC addresses.

[mreece]

I suppose that you could ping all the IP addresses in your local subnet and then check the arp cache

fyi, often pinging the broadcast address (ie, 192.168.2.255) will suffice for this.

[shmem]

Sure, just search CPAN (Arp)...

[tirwhan]

Non-perl solution, but if this is something you need to do often I recommend running arpwatch on a machine that is always connected to the network. You can then simply retrieve the IP address under which a given MAC last showed up from the arpwatch database.

Alternatively (if you really just want to do this once), you can use the arping utility to check every IP address on your network segment until you get a response with the matching MAC address. This puts less load on the network than similar solutions using nmap or ICMP ping because only the initial ARP request is sent and no further packets (this also means it's a lot faster on large networks). arping also has an option to search for a MAC address directly, but that relies on the host in question to respond to an ICMP broadcast ping, which many hosts will not be configured to do.

[gt8073a]

If your on a switched network, you'll need to get mac addresses from the switches. Look into Net::SNMP, or Net::Telnet, or even Net::SSH.

Remember, the mac may been flushed from a device's memory if it hasn't been seen in a while. So, you may need to ping sweep your entire network. nmap, unicorn, or paketto are 3 pretty well known scanners to check out.