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Using Perl Net::IP to Manipulate IPv4 Addresses

In a previous post, I demonstrated a Korn shell script which determined the subnet mask for a range of IPv4 addresses. Perl has a module called Net::IP which provides a number of functions which can be used to manipulate IPv4 (and also IPv6) addresses to provide the same information and a lot more besides. For example, the following code outputs a lot of information about a classless prefix: use Net::IP; my $ip = new Net::IP (‘’) or die (Net::IP::Error()); print ("IP : ".$ip->ip()."n"); print ("Sho : ".$ip->short()."n"); print ("Bin : ".$ip->binip()."n"); print ("Int : ".$ip->intip()."n"); print ("Mask: ".$ip->mask()."n"); print ("Last:

Calculate IPv4 Subnet Mask and Prefix

Here is a simple ksh93 script which I recently wrote to calculate the subnet mask and prefix when given a range of IPv4 addresses. It makes use of the bit manipulation facilities available in ksh93. #!/bin/ksh93 [[ $# != 2 ]] && { echo "Usage: $0 ipaddress1 ipaddress2" exit 1 } SaveIFS=$IFS IFS="./" typeset -a IParr1=($1) typeset -a IParr2=($2) IFS=$SaveIFS typeset -i2 ip11=${IParr1[0]} typeset -i2 ip12=${IParr1[1]} typeset -i2 ip13=${IParr1[2]} typeset -i2 ip14=${IParr1[3]} typeset -i2 ip21=${IParr2[0]} typeset -i2 ip22=${IParr2[1]} typeset -i2 ip23=${IParr2[2]} typeset -i2 ip24=${IParr2[3]} mask=0; match=1 for ((arr=1; arr < 5; arr++)) do binary_value1="" binary_value2="" for ((b=7; b >= 0;

Spoof an IPv4 ARP Response

This post demonstrates how to spoof the response to an ARP request and thus poison the ARP cache of the requesting computer.