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Ill kill whoever did this....

haha..I'm just getting into it myself for an MCSE test (last one!), it was confusing at first, but I think I've gotten the hang of it now!
 
Ok, so you rather have no network?

If there wasnt subnetting, we wouldve run out of network space a long time ago
 
Not if we used IPv6!!!! hehe...ahh the joys of remembering 64 bits ....Well i think I got the whole thing down, I always had the concept but I was lacking on the math and this book said you cant have a Class C subnet like 255.255.255.128 then they go on to say you can even tho its against the rfc.
 
Hehe, yeah, you can't do that! Unless you do it anyways.

I just set up a network like that a few weeks ago. We only needed ~75 IPs, the ISP gave us 1/2 a class C.

cot
 
What I dont quite get, and maybe one of you can help me with is, why cant they legally (by RFC) have 255.255.255.128 as a class c subnet mask. Apparently it works.. so whats the problem.
 
To really make sense of it all you should work with it in binary instead of the dotted quad notation. Why? Because it will become clear to you what's going on and how it really works. After all that's the way the routers/computers view it, you should be able to do it that way as well.

Go to Barnes and Noble and sit down with the Cisco CCIE series Routing TCP/IP. They have an excellent section in the which explains the real nitty gritty of IP subnetting. The subnetting involves simple Boolean logic (0+0=0 and 1+0=1 and 1+1=0). Trust me, it will all make sense if you can grasp it in binary. 🙂
 
Maybe so, but that's how it really works. There's a reason they spend so much time explaining it in binary terms. 🙂 Trust me. Let some of it sink in, play with it, think about, then step away for a week and come back to it and re-read that stuff and it will probably click for you.
 
You can subnet however you want to. What is against the RFCs is having host bits being more signifigant than network bits.

Find the RFC on CIDR - classless inter-domain routing.

You can do whatever you want. 30bit netmask, no problem. Use subnet 0? Sure. 25bit netmask so you have a "high" and "low" subnet, no one would even blink an eye.

Problems crop up when you do VLSM and your routing protocol's not able to handle it, but even those issues you can get around.

If you don't like subnetting, stay away from networking as a career.
 
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