IP Address Tools

I recently had to do some calculations to carve out big blocks of ip addresses for forwarding and nat rules. They varied by each site I was connecting because of the locally assigned internal address. The calculator I normally use was for different purposes. What I needed was a way to convert a random IP range into CIDR notation for creating the rules. I found a tool to do just that trick.

So I decided to compile a list of these ip address helpers. Here is the collection.

IP Range to CIDR Conversion

Put in any random range of IP addresses and it spits out a minimized list of CIDR blocks needed. Be sure to start with zero and end with 255 if you want the entire class c of a range.

Downloadable calculator


web calculator


Subnet Calculator

The free Solar Winds calculator has four main sections.

Address details – pulls basic lookups

Classful subnet creator – create a list of subnets starting with mask, host bit, number of subnets or number of hosts. This is great for cutting up an ip range into sections to distribute on the network.

CIDR Calculator – this takes and IP address and mask or host bits and lets you know what the full range that it belongs to. This is great when you get that single address and mask from the telco and want to see where the range lives.

Subnet Addresses – this generates the full list of addresses in an assigned subnet. Enter the address and mask provided and get a copy/paste list of your whole range. Great for setting up those documentation of how public ip addresses are assigned in a site.

Downloadable calculator


IP Whois Database

The ever popular who owns that public ip address. Sometimes we can’t lay our hands on the carrier information for a site or we are connecting to a partner network. Or that one hop in the trace route that shows the awful latency. This lets us know who is assigned to that public ip address.

Web listing


What is my public IP

We all need to know where that user that can’t connect is coming from sometimes. Quick, simple and easy to remember.

Web Site


IP Address Tracker

Another free Solarwinds tool that can scan and save responses on subnets in a small database. This could replace that excel spreadsheet we keep on how subnets are used on the sites. But I run it against all the sites periodcially to have a baseline saved when trouble is reported. I can see where computers were previously in dhcp and get a sense for the ping times on the subnet in the past.

Downloadable tool


What are your tools?

Originally Posted March 13, 2010
Last Revised on January 20, 2011