unnamedplayer
12-28-2009, 08:52 PM
Hello all,
I am reading the Network+ study guide and I am on Chapter 8 dealing with subnetting. I actually understand what subnetting is about and how it works and I understand the steps Mr. Lammle provides to find how to get the number of subnets, number of hosts per subnet, etc.
What is actually throwing me for a loop right now as I just started this chapter is how does all this relate to CIDR?
I thought CIDR got rid of classful IP addressing, no? But reading this chapter and Mr. Lammle says that only certain subnet masks/CIDR values can be used with certain classes, for example he says /8 through /15 can only be used on Class A networks.
And then when finding the number of subnets he mentions using the formula 2^x where x is the number of masked bits (borrowed from the host portion of the IP address). Again, this relies on the class of the network.
Can someone help me clear up my confusion in regards to if a custom subnet mask is limited based on what class your IP address falls into? And can you really only use some subnet masks with a specific class?
For example, on a test Windows 2003 box I gave it a private Class B address with a subnet mask of 255.0.0.0 (/8) and it didn't reject it.
As you can probably tell from my post I am a bit confused. Any help would be great!
Thanks!
I am reading the Network+ study guide and I am on Chapter 8 dealing with subnetting. I actually understand what subnetting is about and how it works and I understand the steps Mr. Lammle provides to find how to get the number of subnets, number of hosts per subnet, etc.
What is actually throwing me for a loop right now as I just started this chapter is how does all this relate to CIDR?
I thought CIDR got rid of classful IP addressing, no? But reading this chapter and Mr. Lammle says that only certain subnet masks/CIDR values can be used with certain classes, for example he says /8 through /15 can only be used on Class A networks.
And then when finding the number of subnets he mentions using the formula 2^x where x is the number of masked bits (borrowed from the host portion of the IP address). Again, this relies on the class of the network.
Can someone help me clear up my confusion in regards to if a custom subnet mask is limited based on what class your IP address falls into? And can you really only use some subnet masks with a specific class?
For example, on a test Windows 2003 box I gave it a private Class B address with a subnet mask of 255.0.0.0 (/8) and it didn't reject it.
As you can probably tell from my post I am a bit confused. Any help would be great!
Thanks!