Monday, July 31, 2006

Subnet Mask Calculation

This is memo for myself.

Subnet mask is properly grouping the IP of the machimes together so it can communicate among others. Subnet mask will be something like this:

255.255.255.0 or 255.255.255.128 or 255.255.255.192 or 255.255.255.224 ..so on.

Note the last segment which has binary number as 00000000, 10000000, 11000000, 11100000,.... repectively.

Subnet mask above is showing the first 3 segments as a network address and the last segment as a host address. The host address is related to the IP of other computers.

For example, we have one host, which its IP is 192.168.2.1 in the subnet mask of 255.255.255.0. We can have group of other IP in the same network address which they can communicate each other from

192.168.2.0 - 192.168.2.255.

However, it is a good idea to leave out the first and the last IP because most firewall will use these two for specific purposes.

For how to calculate this group, check out this link.

For how to use it into the firewall, check this link.

Sunday, July 30, 2006

Mathcad VS Mathematica

I always love using mathematic tools for my works. They are extremely useful if you know what I mean. There are a lot of mathematic tools these day -- Mathcad, Mathematica, Matlab -- just to name a few. Out of the three, Matlab is the most flexible, but when it comes to a quick solving, the first two are my choices. When I want to do general calculations, I'll use Mathcad because it is very easy to write equations or symbols. However, when I want to do a symbolic calculation, I'll use Mathematica.

To compare the power of symbolic calculations of both tools, try to do the integral of x/(b+a-sqrt(a^2-x^2))^2 in both Mathcad and Mathematica. You'll be amazed by the power of Mathematica. Try it.