Classful IP Address Tutorial (Interactive Animation 4)

Q1. What is address classification?
Answer: IP address is divided into network ID and host ID. It really is classified into five classes: A, B, C, D, E. The division is primarily based on network mask, a fixed length of leftmost bits assigned to network ID and host ID.

Q2. How to classify IP address?
Answer: IP address has 32 bits (four bytes) and is frequently represented as four decimal numbers a.b.c.d, 1 number per byte. Every number's worth is in between 0~25five. They are classified as follows:
Class A: "a" is 0~127. Network ID is "a" (the leftmost digit). Host ID is "b.c.d " (correct 3 digits)
Class B: "a" is 128~191. Network ID is "a.b" (the left 2 digits). Host ID is "c.d " (the correct 2 digits)
Class C: "a" is 192~223. Network ID is "a.b.c" (the leftmost 3 digits). Host ID is "d " (the rightmost digit)
Class D, E: "a" is 224~25five. Class D addresses are utilized for multicasting. Class E addresses are reserved for scientific study.

Q3. How numerous host IDs and network IDs for class A, B, C addresses?
Answer: The number of host/network IDs is determined by the number of bytes allocated for Every class.
Class Host-IDs Network-IDs Usage

A: 16,777,216 256 Very big networks

B: 65,536 65,536 Big networks

C: 256 16,777,216 Little networks. Each and every consists of no much more than 256 computer systems.
Note: In Every single class, two host IDs are reserved and can't be assigned to hosts: all 0 bits, all 1 bits.

Q4. How to determine classes when IP addresses are presented in binary?
Answer: We can just appear at the initial byte (leftmost 3 bits)

Number of left- Leftmost byte a.b.c.d
Class most bits, worth in binary (four-decimals)

A: 1 bit: 0 0xxxxxxx a is 0~127

B: 2 bit: ten 10xxxxxx a is 128~191

C: 3 bit: 110 110xxxxx a is 192~223
Note: The partnership in between classful address and routing table location network is much more clear when playing the companion animation.

Q5. How effectively does classful address work?
Answer: It worked effectively in the early stage of Net when there have been not also numerous computer systems connected to Net. Even so, classifying IP addresses by fixed length of bit does not scale nicely when the number of networks increases.

For instance, how to assign a network address for a group of 1000 computer systems? 1 class C network is not adequate. If allocate a class B address space for this group, there are 64,536 host IDs unused. It really is a substantial waste.

To resolve this dilemma, laptop or computer scientists created classless IP address (or subnetting) to additional divide a classful address space into Small networks. This way, a group of 1000 computer systems can match into a network address that consists of 1024 hosts.

To understand classless IP address, see subsequent tutorial: IP subnetting.

This report is the FAQ of an interactive animation. Ideas are less complicated to grasp when seeing visualizd topology, packets, and tables in this animation. It's listed under External hyperlinks.

External hyperlinks:
1. Classful IP address (this write-up): http://pre.visualland.net/view.php?cid=970&protocol=IPAddress&title=four.%20Classful%20IP%20Address
2. IP address overview: http://pre.visualland.net/protocol.overview.php?p=IPAddress&protocol=&title=0.IPAddress%20Overview