Slightly-Offtopic - Networking audit question

[Travis Roy]

My company is doing an audit to find out what customers are connected to 
  what switch ports.

Normally this would be done by just looking at the cable, but due to 
remote locations and improperly labeled cables we are doing it a 
different way.

This is our current procedure:

1.  Determine one of the IP addresses that the customer is using.

2.  Telnet to the router in the facility you are located in.  Enter 
enable mode.

3.  At the prompt, type "show arp | include [IP ADDRESS]":


4.  The output will look like the following:

Internet  xxx.xxx.xxx.xxx          59   yyyy.yyyy.yyyy  ARPA 
FastEthernet0/0/0

5.  The important part here is the mac address, which is the 
'yyyy.yyyy.yyyy' portion

6.  Next, telnet into the first switch at the facility.

7.  Type in "show mac | include [MAC ADDRESS FROM ABOVE]":

show mac | include yyyy.yyyy.yyyy

8.  The output will look like this:

yyyy.yyyy.yyyy       Dynamic          1  FastEthernet0/6

9.  This indicates that it is connected to FastEthernet0/6.  You are NOT 
done, however.  Because when we look up port 6, we see that is actually 
a feed to a different switch.

10.  We now telnet to the next switch, and issue the same command:

show mac | include yyyy.yyyy.yyyy

15.  The output is as follows:

yyyy.yyyy.yyyy       Dynamic          1  FastEthernet0/17

16.  We look up port 17 and see that it is otherwise unallocated, so it 
must be the port of our customer.

---- END PROCEDURE ----

Okay, so basically what I'm looking for, is there an easier way to do 
this? What would be good options to automate this? I have our IP ranges, 
it would be nice to just feed them in then get a list of what IPs are 
connect to whatever switch port.