|
Home > Archive > CCNA > October 2000 > explain IP classless....
You are viewing an archived Text-only version of the thread.
To view this thread in it's original format and/or if you want to reply to
this thread please [click here]
| Author |
explain IP classless....
|
|
|
| hi,
What is IP classless? Differance bet. IP classless and IP classful?
When should i use this command on a router?
| |
|
| when you divide a class A, B, or C IP address into subnets that new address with its subnet becomes classless. | |
|
| Can someone elaborate on that....thanks | |
|
| Classless Interdomain Routing (CIDR)
CIDR provides a more efficietmethod of allocating IP address space by removing the concept of classes, such as A, B, and C. CIDR associates a value (bit mask) with each IP address that identifies the number of bits used to identify the network portion of the IP address.
/16 and /24 refer to the number of bits of the network part of the IP address. A former class B address might appear as 172.24.0.0/16, which is the same as 256 class Cs, which can appear as 192.200.0.0/16. A single class C appears as 192.201.1.0/24 when using CIDR. This new “look” to IP addresses consists of an IP address and a mask length. A mask length is often called an “IP prefix.” The mask length specifies the number of left-most contiguous significant bits in the corresponding IP address.
For example, the CIDRized IP address of 172.24.0.0/16 indicates you are using 172.24.0.0 255.255.0.0. The /16 is an indication that you are using 16 bits of the mask when counting from the far left.
------------------
Lanny
A+/MCP/CCNA
CCNA/CCDA Study Group Page | |
|
| What is the difference between classful IP addressing and classless IP addressing?
The difference between classful IP addressing and classless IP addressing is in selecting the number of bits used for the network ID portion of an IP address. In classful IP addressing, the network ID portion can take only the predefined number of bits 8, 16, or 24. In classless addressing, any number of bits can be assigned to the network ID.
Source from: http://www.geocities.com/~yega/network/cidr.html#A6
| |
|
| correct mi if i'm wrong:
Classless:
150.150.0.0/20
(I can use any amt of "/bits" i prefer?)
Classful:
150.150.0.0/16
(i need to use "/16" as that is a classB IP, nothing else?) | |
|
| assuming, that you get this classB-address-pool from internic for your internet-access:
150.150.0.0/16
then you have 65.534 possible hosts within only one network. but you want to subdivide that large host-pool into some subnets because of the need of differnet locations or different security-areas or different broadcast-domains or what else...
then you will decide to use classless ip-addresses.
150.150.0.0/20
now you can use 14 (forum-member subnet_zero would say 15) different subnets within the former network-pool. your possible host-amount per subnet will go down to 4.094
siegi |
|
|
|
|