7 replies to this topic

[tha_dub]

I offered this method to a buddy of mine for remembering address classes and he said it helped him a lot so I figured I'd post it here too.

If you are studying for a CCNA you will almost certainly memorize all these address classes along the way. My simplified trick is to remember only 2 pieces of information for the classes.

127, and 192.


anything before 127 is class A, 192 and over is Class C obviously the middle is class b.
127 is loopback.

[ryeguy146]

I tried that for awhile, but was presented with a problem when I didn't remember where class C ended and class D began. So, I sorted it all out and now memorize just one small table

00000000-01111111
10000000-10111111
11000000-11011111

This is the basic binary form of the first three IP blocks. Notice the patterns that make it easy to remember? Now, to convert it, just remember what each bit represents:

128, 64, 32, 16, 8, 4, 2, 1

Start at 128 and just divide by two for each iteration until you reach one. Eight bits. Using this, we can do the math and figure out what each block is. I use this method and write the following table down whenever I need to remember IPs. This is, of course, for only the first octet, but it is the only one that matters for classes.

00000000-01111111 : A : 0-127 (64+32+16+8+4+2+1)
10000000-10111111 : B : 128-191
11000000-11011111 : C : 192-223

If you wanted to continue down, you could just continue the pattern in the binary...

00000000-01111111
10000000-10111111
11000000-11011111
11100000-11101111
11110000-11110111

...this has solved all of my problems in memorizing IP addressing information. Just remember the binary!

[templarvisonz]

Thanks for the post. I think this method will work for me when remembering the address classes.

Arbitor

[ryeguy146]

I've also noticed that my style of memorizing the IP classes has allowed me to easily learn subnetting. I don't know if that's an issue with anyone else, but I found the transition smooth after thinking of IPs in binary for so long.

[aurelius2000]

Great posts!  I will be using that ryeguy.  I have somewhat of a hard time with networking when it comes to classes and subnetting.

If you can, can you either message me or post your trick for subnetting?

Props to both tricks!  I am baffled that i did not find something like this sooner.  

Maybe post it in the IT Cert forum?

[Kameha]

COOL TIP MAN
thank you

[timtom22]

I tried that for awhile, but was presented with a problem when I didn't remember where class C ended and class D began. So, I sorted it all out and now memorize just one small table

00000000-01111111
10000000-10111111
11000000-11011111

This is the basic binary form of the first three IP blocks. Notice the patterns that make it easy to remember? Now, to convert it, just remember what each bit represents:

128, 64, 32, 16, 8, 4, 2, 1

Start at 128 and just divide by two for each iteration until you reach one. Eight bits. Using this, we can do the math and figure out what each block is. I use this method and write the following table down whenever I need to remember IPs. This is, of course, for only the first octet, but it is the only one that matters for classes.

00000000-01111111 : A : 0-127 (64+32+16+8+4+2+1)
10000000-10111111 : B : 128-191
11000000-11011111 : C : 192-223

If you wanted to continue down, you could just continue the pattern in the binary...

00000000-01111111
10000000-10111111
11000000-11011111
11100000-11101111
11110000-11110111

...this has solved all of my problems in memorizing IP addressing information. Just remember the binary!

Good way to understand.
When I was studying for CCNA, I remembered it as follows,

Class A address starts with 0XXXXXXX
Class B address starts with 10XXXXXX
Class C address starts with 110XXXXX
Class D address starts with 1110XXXX.

I remember doing some practice questions, where the entire IP address is given in Binary and they ask you what class it belongs to and such. So all you have to do is just look at first 4 bits to get your answer (as opposed to adding binary numbers).

Helpful? Comment as you see fit.....

Edited by timtom22, 16 October 2011 - 09:04 AM.

[timtom22]

Class A doesn't always start with 01, but does start with 0.

Thanks for pointing out the  typo (I just fixed it). However, I am sure you knew what I meant.