
VSG-1200 User’s Guide
Appendix H IP Subnetting
267
For example, 192.1.1.0 /25 is equivalent to saying 192.1.1.0 with mask 255.255.255.128.
The following table shows all possible subnet masks for a class “C” address using both
notations.
The first mask shown is the class “C” natural mask. Normally if no mask is specified it is
understood that the natural mask is being used.
Example: Two Subnets
As an example, you have a class “C” address 192.168.1.0 with subnet mask of 255.255.255.0.
The first three octets of the address make up the network number (class “C”). You want to
have two separate networks.
Divide the network 192.168.1.0 into two separate subnets by converting one of the host ID bits
of the IP address to a network number bit. The “borrowed” host ID bit can be either “0” or “1”
thus giving two subnets; 192.168.1.0 with mask 255.255.255.128 and 192.168.1.128 with
mask 255.255.255.128.
Table 99
Alternative Subnet Mask Notation
SUBNET MASK IP ADDRESS
SUBNET MASK “1” BITS
LAST OCTET BIT VALUE
255.255.255.0
/24
0000 0000
255.255.255.128
/25
1000 0000
255.255.255.192
/26
1100 0000
255.255.255.224
/27
1110 0000
255.255.255.240
/28
1111 0000
255.255.255.248
/29
1111 1000
255.255.255.252
/30
1111 1100
Table 100
Two Subnets Example
NETWORK NUMBER
HOST ID
IP Address
192.168.1.
0
IP Address (Binary)
11000000.10101000.00000001.
00000000
Subnet Mask
255.255.255.
0
Subnet Mask (Binary)
11111111.11111111.11111111.
00000000
Note:
In the following charts, shaded/bolded last octet bit values indicate host
ID bits “borrowed” to form network ID bits. The number of “borrowed” host ID
bits determines the number of subnets you can have. The remaining number
of host ID bits (after “borrowing”) determines the number of hosts you can
have on each subnet.
Summary of Contents for VSG-1200
Page 1: ...VSG 1200 Vantage Service Gateway User s Guide Version 1 08 1 2006 ...
Page 8: ...VSG 1200 User s Guide 8 Customer Support ...
Page 22: ...VSG 1200 User s Guide 22 List of Figures ...
Page 26: ...VSG 1200 User s Guide 26 List of Tables ...
Page 40: ...VSG 1200 User s Guide 40 Chapter 2 Hardware Installation and Connection ...
Page 45: ...VSG 1200 User s Guide Chapter 3 The Web Configurator 45 Figure 13 System Setting System ...
Page 52: ...VSG 1200 User s Guide 52 Chapter 3 The Web Configurator ...
Page 64: ...VSG 1200 User s Guide 64 Chapter 4 LAN WAN and Server Setup ...
Page 74: ...VSG 1200 User s Guide 74 Chapter 6 Authentication Figure 29 System Setting Authentication ...
Page 102: ...VSG 1200 User s Guide 102 Chapter 9 Dynamic Subscriber Accounts ...
Page 128: ...VSG 1200 User s Guide 128 Chapter 13 Subscriber Information Window ...
Page 136: ...VSG 1200 User s Guide 136 Chapter 14 Account Printout ...
Page 140: ...VSG 1200 User s Guide 140 Chapter 15 User Agreement Page ...
Page 144: ...VSG 1200 User s Guide 144 Chapter 16 Bandwidth Management ...
Page 158: ...VSG 1200 User s Guide 158 Chapter 19 LAN Devices ...
Page 162: ...VSG 1200 User s Guide 162 Chapter 20 Static Route ...
Page 170: ...VSG 1200 User s Guide 170 Chapter 21 Syslog and Session Trace ...
Page 174: ...VSG 1200 User s Guide 174 Chapter 22 SNMP ...
Page 198: ...VSG 1200 User s Guide 198 Chapter 25 Secure Socket Layer ...
Page 206: ...VSG 1200 User s Guide 206 Chapter 26 The SMT ...
Page 214: ...VSG 1200 User s Guide 214 Chapter 27 LAN and WAN Setup Using the SMT ...
Page 226: ...VSG 1200 User s Guide 226 Chapter 28 Configuration and Firmware Maintenance ...
Page 236: ...VSG 1200 User s Guide 236 Appendix B IP Address Assignment Conflicts ...
Page 238: ...VSG 1200 User s Guide 238 Appendix C Subscriber Login ...
Page 242: ...VSG 1200 User s Guide 242 Appendix D Vendor Specific Attributes ...
Page 252: ...VSG 1200 User s Guide 252 Appendix F Cable Types and Cable Pin Assignments ...
Page 264: ...VSG 1200 User s Guide 264 Appendix G Setting up Your Computer s IP Address ...
Page 272: ...VSG 1200 User s Guide 272 Appendix H IP Subnetting ...