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  1. Agustin's Linux Manual
  2. Networks & Servers
  3. About the Author
  4. Table of Contents
  5. IP Addresses Networks and Subnets
  6. Network Classes
  7. IP Address in Decimal Notation
  8. Sub-netting
  9. Designing Subnets
  10. Allocating Subnets
  11. Defining Host Addresses
  12. Variable Length Subnet Mask
  13. Routing Protocols
  14. Classless Internet Domain Routing
  15. Servers - Chapter 9
  16. Apache Web Server
  17. Configuring Apache
  18. Uploading Web Pages
  19. Apache Overview
  20. MIMEMagic
  21. DNS Servers
  22. Welcome to Webmin
  23. Creating the Master Domain
  24. Adding the Reverse Zone
  25. Querying the DNS server
  26. Adding Virtual Domain to DNS Server
  27. Reverse Zone for Virtual Zone
  28. Binding IP Address for Virtual Domain
  29. Virtual Web Hosting
  30. DNS Security Options
  31. FTP Server
  32. Securing the FTP Server
  33. Email Server
  34. Postfix Configuration
  35. Dealing with Identical Users
  36. Configuring Email Clients
  37. Configuring Outlook
  38. Samba Server
  39. Configuring SAMBA Server
  40. The smb.conf File
  41. smb.conf Analysis
  42. Adding Users to Samba

IP Address in Decimal Notation

Reading IP addresses would be very difficult if we actually used its binary notation or hexadecimal notation. To simplify the reading, a standard was developed known as the doted decimal notation, which divides a 32-bit IP address into a four 8-bit.

Look at the following figure.

IP addresses
Fig 8.3

Figure 8.3 demonstrates a Class B network, doted in decimal notation. Now it simplifies the reading doesn't it?
So how do we recognize what type of network are we dealing with? The following table may answer the question.

Subnet ClassesDotted Decimal
ClassHigh Bit
Order 		Range
A /8 Prefixes01.xxx.xxx.xxx through 126.xxx.xxx.xxx
B /16 Prefixes10128.0.xxx.xxx through 191.255.xxx.xxx
C /24 Prefixes110192.0.0.xxx through 223.255.255.xxx
Table 8.1

Note. 127.0.0.1 is out of the table, because this address is the reserved loop back.

As you have already noticed, the classes A, B and C are easy to understand, and easy to allocate, but the allocation of addresses is truly inefficient because there are no classes to support medium sized networks.

If you notice a Class C, /24 which supports 254 hosts is too small and a class B /16 which support 65,534 hosts is too big. And assigning either one to an organization really makes a great impact when increasing the size of the Internet's routing table.
Anyways, if you are working in a private LAN behind a router or proxy server, you are probably using a Class C or Class B. Many system administrators are unaware of why they are using these types of networks; others don't even know that classes exist. All they know is that they have to place a subnet mask.