Subnetting trick

I've not been doing any true networking for quite some time, so the bits I picked up in college have been growing mental mold in my head. I've forgotten much of what I learned about subnetting, so when I had to quickly figure out what slash notation our mask was, it was Google to the rescue, or more accurately, mark-scott to the rescue! I've summed it up below. Click the link for a much better explanation.

Link to original content:

So you know what the mask is, but you need to quickly figure out what the slash notation is?

Basically, remember these numbers:

1 128
2 192
3 224
4 240
5 248
6 252
7 254
8 255

Consider each octet of the example:

If you add 8 (255) + 8 (255) + 6 (252) = 22

So = /22

How cool is that??? Thanks mark-scott, wherever you are!


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