Archive for tag: arp

Find live IP addresses on your network

Sometimes it can be the simplest of things which are the hardest to do. An example is finding details of IP address allocation and usage on the network.

The built-in ARP command will tell you the IP addresses which have recently been accessed on the network.

C:>arp -a
Interface: 192.168.3.30 --- 0xb
Internet Address Physical Address Type 192.168.3.1 64-31-50-d2-ae-04 dynamic 192.168.3.3 00-13-72-1b-2a-de dynamic 192.168.3.22 00-1a-a0-25-87-42 dynamic 192.168.3.27 00-1f-29-34-8e-94 dynamic

 

However, this won't show you devices which are on, but not currently communicating with your PC. For this, you need to scan the network.

This command will ping all addresses in your class C network from .1 to .254 and display the result of the ping if the address responds:

C:\>for /L %a in (1,1,254) do @ping -n 1 192.168.3.%a|find "TTL"
Reply from 192.168.3.1: bytes=32 time<1ms TTL=128
Reply from 192.168.3.3: bytes=32 time<1ms TTL=128
Reply from 192.168.3.4: bytes=32 time<1ms TTL=128
Reply from 192.168.3.9: bytes=32 time<1ms TTL=64
Reply from 192.168.3.17: bytes=32 time=2ms TTL=128
Reply from 192.168.3.22: bytes=32 time=2ms TTL=12
Reply from 192.168.3.27: bytes=32 time=2ms TTL=128
Reply from 192.168.3.41: bytes=32 time=1ms TTL=128

 

As you can see, this has picked up some addresses which we didn't see in the ARP list.

The command is actually sending a single ping to each address in the range but only displaying those which respond as being 'alive'.

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