Free IP address script

[Guest anon]

Here is a cool script i found/stole at http://www.brandonhutchinson.com

tried it out and it works

We frequently have to assign static IP addresses to servers and certain workstations. Although the following script does not guarantee that the IPs returned are not currently in use or are reserved for future use, it performs the following checks:

 

* ICMP ECHO REQUEST (ping)

* DNS PTR (reverse) lookup

* TCP Connect scan using nmap for common services

 

If an IP address does not respond to a ping, does not have a DNS PTR record, and is not listening for common services, it is considered available for assignment.

 

#!/bin/sh

 

# For each of the IPs specified, try an ICMP ECHO REQUEST (ping),

# reverse DNS (PTR) lookup, and port scan for open $SERVICES.

# If the host does not respond to a ping, has no DNS PTR entry,

# and does not have open ports listed in the $SERVICES variable,

# it is considered available for assignment.

 

if [ -z $@ ] ; then

  echo "  Usage: ./free_ips.sh {IP_range}"

  echo "Example: ./free_ips.sh 192.168.1.1-100"

  exit 1

fi

 

# SERVICES is the list of ports to scan on the host

SERVICES=21,22,23,25,53,80,137,138,139,443,445

 

for i in `nmap -sP -v $1 | grep down | awk '{print $2}' | tr -d '()'`

do

  # Does a DNS PTR record exist?

  dig -x $i | grep NXDOMAIN > /dev/null 2>&1

  if [ $? -eq 0 ] ; then

      # Are any of the ports listed in $SERVICES open?

      nmap -P0 -p $SERVICES -T Aggressive $i | grep open > /dev/null 2>&1

      if [ $? -eq 1 ] ; then

        echo $i

      fi

  fi

done

Last modified: 05/08/2003

[SoulSe]

Sweet!

 

Thanks for stealing that for us anon. A verible Robin Hood you are.