ZyWALL 35 User’s Guide
Appendix C IP Subnetting
593
A
P P E N D I X
C
IP Subnetting
IP Addressing
Routers “route” based on the network number. The router that delivers the data packet to the
correct destination host uses the host ID.
IP Classes
An IP address is made up of four octets (eight bits), written in dotted decimal notation, for
example, 192.168.1.1. IP addresses are categorized into different classes. The class of an
address depends on the value of its first octet.
• Class “A” addresses have a 0 in the left most bit. In a class “A” address the first octet is
the network number and the remaining three octets make up the host ID.
• Class “B” addresses have a 1 in the left most bit and a 0 in the next left most bit. In a class
“B” address the first two octets make up the network number and the two remaining
octets make up the host ID.
• Class “C” addresses begin (starting from the left) with 1 1 0. In a class “C” address the
first three octets make up the network number and the last octet is the host ID.
• Class “D” addresses begin with 1 1 1 0. Class “D” addresses are used for multicasting.
(There is also a class “E” address. It is reserved for future use.)
Note:
Host IDs of all zeros or all ones are not allowed.
Therefore:
A class “C” network (8 host bits) can have 2
8
–2 or 254 hosts.
A class “B” address (16 host bits) can have 2
16
–2 or 65534 hosts.
A class “A” address (24 host bits) can have 2
24
–2 hosts (approximately 16 million hosts).
Table 12
Classes of IP Addresses
IP ADDRESS:
OCTET 1
OCTET 2
OCTET 3
OCTET 4
Class A
0
Network number
Host ID
Host ID
Host ID
Class B
10
Network number
Network number
Host ID
Host ID
Class C
110
Network number
Network number
Network number
Host ID
Summary of Contents for ZyXEL ZyWALL 35
Page 1: ...ZyWALL 35 Internet Security Appliance User s Guide Version 3 64 3 2005 ...
Page 2: ......
Page 38: ...ZyWALL 35 User s Guide 36 ...
Page 46: ...ZyWALL 35 User s Guide 44 ...
Page 74: ...ZyWALL 35 User s Guide 72 Chapter 2 Introducing the Web Configurator ...
Page 90: ...ZyWALL 35 User s Guide 88 Chapter 3 Wizard Setup ...
Page 100: ...ZyWALL 35 User s Guide 98 Chapter 4 LAN Screens ...
Page 106: ...ZyWALL 35 User s Guide 104 Chapter 5 Bridge Screens ...
Page 128: ...ZyWALL 35 User s Guide 126 Chapter 6 Wireless LAN ...
Page 135: ...ZyWALL 35 User s Guide Chapter 7 WAN Screens 133 Figure 47 General ...
Page 152: ...ZyWALL 35 User s Guide 150 Chapter 7 WAN Screens Figure 57 Dial Backup Setup ...
Page 158: ...ZyWALL 35 User s Guide 156 Chapter 7 WAN Screens ...
Page 166: ...ZyWALL 35 User s Guide 164 Chapter 8 DMZ Screens ...
Page 234: ...ZyWALL 35 User s Guide 232 Chapter 13 Introduction to IPSec ...
Page 275: ...ZyWALL 35 User s Guide Chapter 15 Certificates 273 Figure 129 My Certificate Details ...
Page 294: ...ZyWALL 35 User s Guide 292 Chapter 16 Authentication Server Figure 140 Local User Database ...
Page 314: ...ZyWALL 35 User s Guide 312 Chapter 17 Network Address Translation NAT ...
Page 318: ...ZyWALL 35 User s Guide 316 Chapter 18 Static Route ...
Page 324: ...ZyWALL 35 User s Guide 322 Chapter 19 Policy Route ...
Page 340: ...ZyWALL 35 User s Guide 338 Chapter 20 Bandwidth Management ...
Page 376: ...ZyWALL 35 User s Guide 374 Chapter 22 Remote Management ...
Page 390: ...ZyWALL 35 User s Guide 388 Chapter 24 Logs Screens Figure 198 Log Settings ...
Page 413: ...ZyWALL 35 User s Guide Chapter 25 Maintenance 411 Figure 220 Restart Screen ...
Page 414: ...ZyWALL 35 User s Guide 412 Chapter 25 Maintenance ...
Page 440: ...ZyWALL 35 User s Guide 438 Chapter 28 WAN and Dial Backup Setup ...
Page 456: ...ZyWALL 35 User s Guide 454 Chapter 31 DMZ Setup ...
Page 460: ...ZyWALL 35 User s Guide 458 Chapter 32 Route Setup ...
Page 470: ...ZyWALL 35 User s Guide 468 Chapter 33 Remote Node Setup ...
Page 522: ...ZyWALL 35 User s Guide 520 Chapter 39 System Information Diagnosis ...
Page 538: ...ZyWALL 35 User s Guide 536 Chapter 40 Firmware and Configuration File Maintenance ...
Page 550: ...ZyWALL 35 User s Guide 548 Chapter 42 Remote Management ...
Page 558: ...ZyWALL 35 User s Guide 556 Chapter 43 IP Policy Routing ...
Page 574: ...ZyWALL 35 User s Guide 572 Chapter 45 Troubleshooting Figure 364 Java Sun ...
Page 602: ...ZyWALL 35 User s Guide 600 Appendix C IP Subnetting ...
Page 608: ...ZyWALL 35 User s Guide 606 Appendix E PPTP ...
Page 626: ...ZyWALL 35 User s Guide 624 Appendix G Triangle Route ...
Page 656: ...ZyWALL 35 User s Guide 654 Appendix J Importing Certificates ...
Page 658: ...ZyWALL 35 User s Guide 656 Appendix K Command Interpreter ...
Page 664: ...ZyWALL 35 User s Guide 662 Appendix L Firewall Commands ...
Page 668: ...ZyWALL 35 User s Guide 666 Appendix M NetBIOS Filter Commands ...
Page 674: ...ZyWALL 35 User s Guide 672 Appendix O Brute Force Password Guessing Protection ...
Page 696: ...ZyWALL 35 User s Guide 694 Appendix Q Log Descriptions ...