New Tool: IP Range to CIDR

Posted January 17, 2010 – 23:40 in: Nullamatix, syndicated

At least twice a week I find myself visiting ip2cidr.com, the IP to CIDR converter. Since the owner/author of the site hasn’t release the source code, and I love a challenge, I developed my own version. The guys at the job find the tool useful, and after a few minor bug fixes, I’ve made the IP Range to CIDR tool available for use here at Nullamatix.com.

Using IP to CIDR

The tool is very easy to use. The first text input field is the first IP address or start of the range. The second text input field is the second IP address or end of the range. For instance, supplying 172.0.0.0 in the first field and 192.168.255.255 in the second field will produce:

192.0.0.0/9
192.128.0.0/11
192.160.0.0/13
192.168.0.0/16
172.0.0.0/6
176.0.0.0/4

172.16.0.0 and 172.17.255.255 will produce:

172.16.0.0/15

I’ll eventually implement on-the-fly htaccess, null route, and iptables policy generation.

IPtables Drop Policies

In addition to the new IP Range to CIDR tool, I’ve also added drop lists for ThePlanet, Softlayer, APNIC, and Amazon, courtesy of robtex.com. While looking over firewall and httpd access logs, malicious attacks and comment spam seem to originate from these sources the most. If there’s a network or company you’d like me to add, just submit a comment to this post.