Subnetting

[ikendo]

Hi guys,

As im reading Sybex CCNA 607 book. I noticed that Todd is using the production ip scheme. For example on class B or A , he is using like 255.255.255.192(/26). Does this work on a real world network?, I know it will give your more hosts and subnets. But isnt class B should 255.255.0.0 and class A is 255.0.0.0?. It took me awhile to figure it out that you need to add zero on the 3rd octate...lol duh!!. But it works out the sameway for me.

 

[Ntr0P]

1) Does this work on a real world network?

Absolutely.

2) But isnt class B should 255.255.0.0 and class A is 255.0.0.0?

These are the classful subnets. It is important to understand classes and how they work (as you will see with RIPv1) but to also know that classes are not really used anymore.

The first octet will dicate what class the address is and that in turn dictates the subnet mask used. So as you mentioned, if you determine you have a class A address, the class A subnet mask would be 255.0.0.0 However, since we don't pay too much attention to class anymore, we can use pretty much any subnet mask we want regardless of class.

Hopefully I didn't help confuse you.

 

[ikendo]

Yep I understood what you had said. I still remember when I took the MCSE 4.0(4 years ago). That time they were using only classful ip setting on the TCP/IP exam. On ccna, I guess they based on classless addressing I guess huh?. Anyway thanks for clearing it up.

 

[Ntr0P]

Don't get me wrong, you do need to know classful IP for the CCNA. Don't want to be responsible if you miss any questions on the exam!

 

[ikendo]

NTROP,

Thanks

 

[marsd]

You need to know more than just classful
addressing, you have to understand subnetting, supernetting and the concept of cidr.
My advice is to sit down with your masks
from /16 to /31 and figure out the number of hosts per network and number of subnets.

Then determine the subnet address and
broadcast address for each subnet given
a random ip address and a mask.
Once you can do this,those questions on the
exam will be trivial.

 

[ikendo]

Thanks for replying guys, I got it down packed with classless and classful,CIDR,yada,yada. I was just curious about the whole thang. Thanks for helping me.