Posts Tagged ‘ipv4’

I Tried to Make a Fancy IP Calculator

Friday, February 27th, 2009

Heyhey, I have been playing around with Ajax and Javascript and I made a more fancy IP Calculator.

I have one available on this site (in the menu to the right, use it in case you don’t have javascript enabled).
If you want to try out my fancy version just go to

I haven’t had the chance to try the design in Internet Explorer, so if anyone can email me a screenshot or something it would be just awesome! (It is probably totally broken, because I am not a designer.)

Well, that’s that, enjoy it!

Route overlaps, it’s dangerous!

Sunday, September 14th, 2008

Just wanted to tell you that I added a new page, it’s aIP subnet calculator tool.

It works with IPv4 and IPv6 addresses, just remember to add the network length in the end (/24) for a

The danger with dynamic routing is the possibility of route overlaps, by this I mean having the same subnet defined on two routers announcing it in a dynamic routing protocol like for example OSPF.

Let us say you have configured a customer as and he uses and

Then you get a new customer and configure for example a new subnet, which is a more specific route (CIDR wise).

You might end up effectively blackholing the old customers traffic, this is something one should consider.

Use my IP subnet calculator tool to be sure not to overlap networks!

Cisco wildcard cheat!

Tuesday, September 2nd, 2008

Just wanted to share a little fast cheat for figuring out the wildcard mask for networks!

The wildcard mask is used some places in IOS, for example in the network command in configuration of the OSPF routing process.

To figure out the network wildcard mask, just take each octet in the netmask and subtract it from 255.

For the wildcard mask will then be
For the wildcard mask will be (255 – 252)

Makes work go faster !