Many times I am working on a network where I need to either flush out an ARP table or just see if any hosts respond. So from a Windows system we go to the command prompt and use the for command to setup a basic for loop (like back in the programming days). If you want to see all the options for the “for” command use the:
for /?
Our example is going to the sequence of numbers option “/L”. We are going to need to define 5 things to get our loop to work.
1) Variable: We need to define a variable that will be assigned the values as we loop through them.
2) Start: What number is the sequence is starting at. We will be using 1.
3) Step: What is going to be added to the sequence with each iteration.
4) End: What is the last sequence in the iteration.
5) Command: What command to run, and all its parameters to use
So to put it in context it would look like:
FOR /L %variable IN (start,step,end) DO command [command-parameters]
In my example I am using:
1) Variable: i
2) Start: 1
3) Step: 1
4) End: 254
5) Command: ping 192.168.1 -n 1
Put all together it is:
for /L %i IN (1,1,254) DO ping 192.168.1.%i -n 1
It will walk the whole local network block and ping each host one time. When it runs Below is the output.
Pinging 192.168.1.1 with 32 bytes of data:
Reply from 192.168.1.1: bytes=32 time=287ms TTL=255
Ping statistics for 192.168.1.1:
Packets: Sent = 1, Received = 1, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 287ms, Maximum = 287ms, Average = 287ms
Pinging 192.168.1.2 with 32 bytes of data:
Request timed out.
Ping statistics for 192.168.1.2:
Packets: Sent = 1, Received = 0, Lost = 1 (100% loss),
Pinging 192.168.1.3 with 32 bytes of data:
Request timed out.
Ping statistics for 192.168.1.3:
Packets: Sent = 1, Received = 0, Lost = 1 (100% loss),
.
.
.
Pinging 192.168.1.252 with 32 bytes of data:
Reply from 192.168.1.252: bytes=32 time=244ms TTL=63
Ping statistics for 192.168.1.252:
Packets: Sent = 1, Received = 1, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 244ms, Maximum = 244ms, Average = 244ms
Pinging 192.168.1.253 with 32 bytes of data:
Request timed out.
Ping statistics for 192.168.1.253:
Packets: Sent = 1, Received = 0, Lost = 1 (100% loss),
Pinging 192.168.1.254 with 32 bytes of data:
Request timed out.
Ping statistics for 192.168.1.254:
Packets: Sent = 1, Received = 0, Lost = 1 (100% loss),
Jason Howe, PEI
