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Appendix C IP Addresses and Subnetting
ZyWALL 2WG User’s Guide
731
Subnet masks are expressed in dotted decimal notation just like IP addresses. The following
examples show the binary and decimal notation for 8-bit, 16-bit, 24-bit and 29-bit subnet
masks.
Network Size
The size of the network number determines the maximum number of possible hosts you can
have on your network. The larger the number of network number bits, the smaller the number
of remaining host ID bits.
An IP address with host IDs of all zeros is the IP address of the network (192.168.1.0 with a
24-bit subnet mask, for example). An IP address with host IDs of all ones is the broadcast
address for that network (192.168.1.255 with a 24-bit subnet mask, for example).
As these two IP addresses cannot be used for individual hosts, calculate the maximum number
of possible hosts in a network as follows:
Notation
Since the mask is always a continuous number of ones beginning from the left, followed by a
continuous number of zeros for the remainder of the 32 bit mask, you can simply specify the
number of ones instead of writing the value of each octet. This is usually specified by writing
a “/” followed by the number of bits in the mask after the address.
For example, 192.1.1.0 /25 is equivalent to saying 192.1.1.0 with subnet mask
255.255.255.128.
The following table shows some possible subnet masks using both notations.
Table 261
Subnet Masks
BINARY
DECIMAL
1ST
OCTET
2ND
OCTET
3RD
OCTET
4TH OCTET
8-bit mask
11111111
00000000
00000000
00000000
255.0.0.0
16-bit mask
11111111
11111111
00000000
00000000
255.255.0.0
24-bit mask
11111111
11111111
11111111
00000000
255.255.255.0
29-bit mask
11111111
11111111
11111111
11111000
255.255.255.248
Table 262
Maximum Host Numbers
SUBNET MASK
HOST ID SIZE
MAXIMUM NUMBER OF HOSTS
8 bits
255.0.0.0
24 bits
2
24
– 2
16777214
16 bits
255.255.0.0
16 bits
2
16
– 2
65534
24 bits
255.255.255.0
8 bits
2
8
– 2
254
29 bits
255.255.255.248 3 bits
2
3
– 2
6
Table 263
Alternative Subnet Mask Notation
SUBNET MASK
ALTERNATIVE
NOTATION
LAST OCTET
(BINARY)
LAST OCTET
(DECIMAL)
255.255.255.0
/24
0000 0000
0
255.255.255.128
/25
1000 0000
128
Содержание ZYWALL 2 WG
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Страница 8: ...Safety Warnings ZyWALL 2WG User s Guide 8 ...
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Страница 50: ...List of Tables ZyWALL 2WG User s Guide 50 ...
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Страница 80: ...Chapter 2 Introducing the Web Configurator ZyWALL 2WG User s Guide 80 ...
Страница 100: ...Chapter 3 Wizard Setup ZyWALL 2WG User s Guide 100 ...
Страница 140: ...Chapter 4 Tutorial ZyWALL 2WG User s Guide 140 ...
Страница 145: ...145 PART II Network and Wireless LAN Screens 147 Bridge Screens 159 WAN Screens 165 DMZ Screens 201 Wireless LAN 211 ...
Страница 146: ...146 ...
Страница 158: ...Chapter 6 LAN Screens ZyWALL 2WG User s Guide 158 ...
Страница 171: ...Chapter 8 WAN Screens ZyWALL 2WG User s Guide 171 Figure 108 NETWORK WAN General ...
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Страница 238: ...238 ...
Страница 258: ...Chapter 11 Firewall ZyWALL 2WG User s Guide 258 Figure 159 SECURITY FIREWALL Rule Summary Edit ...
Страница 270: ...Chapter 11 Firewall ZyWALL 2WG User s Guide 270 Figure 170 My Service Firewall Rule Example Rule Summary Completed ...
Страница 300: ...Chapter 13 Content Filtering Reports ZyWALL 2WG User s Guide 300 ...
Страница 313: ...Chapter 14 IPSec VPN ZyWALL 2WG User s Guide 313 Figure 199 SECURITY VPN VPN Rules IKE Edit Gateway Policy ...
Страница 322: ...Chapter 14 IPSec VPN ZyWALL 2WG User s Guide 322 Figure 202 SECURITY VPN VPN Rules IKE Edit Network Policy ...
Страница 348: ...Chapter 14 IPSec VPN ZyWALL 2WG User s Guide 348 ...
Страница 360: ...Chapter 15 Certificates ZyWALL 2WG User s Guide 360 Figure 229 SECURITY CERTIFICATES My Certificates Create Basic ...
Страница 378: ...Chapter 15 Certificates ZyWALL 2WG User s Guide 378 ...
Страница 380: ...Chapter 16 Authentication Server ZyWALL 2WG User s Guide 380 Figure 239 SECURITY AUTH SERVER Local User Database ...
Страница 384: ...384 ...
Страница 426: ...Chapter 20 Bandwidth Management ZyWALL 2WG User s Guide 426 ...
Страница 479: ...479 PART V Logs and Maintenance Logs Screens 481 Maintenance 511 ...
Страница 480: ...480 ...
Страница 485: ...Chapter 26 Logs Screens ZyWALL 2WG User s Guide 485 Figure 304 LOGS Log Settings ...
Страница 510: ...Chapter 26 Logs Screens ZyWALL 2WG User s Guide 510 ...
Страница 530: ...530 ...
Страница 558: ...Chapter 30 WAN and Dial Backup Setup ZyWALL 2WG User s Guide 558 ...
Страница 564: ...Chapter 31 LAN Setup ZyWALL 2WG User s Guide 564 ...
Страница 570: ...Chapter 32 Internet Access ZyWALL 2WG User s Guide 570 ...
Страница 574: ...Chapter 33 DMZ Setup ZyWALL 2WG User s Guide 574 ...
Страница 578: ...Chapter 34 Route Setup ZyWALL 2WG User s Guide 578 ...
Страница 582: ...Chapter 35 Wireless Setup ZyWALL 2WG User s Guide 582 ...
Страница 594: ...Chapter 37 IP Static Route Setup ZyWALL 2WG User s Guide 594 ...
Страница 614: ...Chapter 38 Network Address Translation NAT ZyWALL 2WG User s Guide 614 ...
Страница 632: ...Chapter 40 Filter Configuration ZyWALL 2WG User s Guide 632 ...
Страница 668: ...Chapter 44 System Maintenance Menus 8 to 10 ZyWALL 2WG User s Guide 668 ...
Страница 672: ...Chapter 45 Remote Management ZyWALL 2WG User s Guide 672 ...
Страница 680: ...Chapter 46 IP Policy Routing ZyWALL 2WG User s Guide 680 ...
Страница 685: ...685 PART VII Troubleshooting and Specifications Troubleshooting 687 Product Specifications 693 ...
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Страница 692: ...Chapter 48 Troubleshooting ZyWALL 2WG User s Guide 692 ...
Страница 702: ...Chapter 49 Product Specifications ZyWALL 2WG User s Guide 702 ...
Страница 704: ...704 ...
Страница 712: ...Appendix A Pop up Windows JavaScripts and Java Permissions ZyWALL 2WG User s Guide 712 ...
Страница 740: ...Appendix D Common Services ZyWALL 2WG User s Guide 740 ...
Страница 768: ...Appendix G Legal Information ZyWALL 2WG User s Guide 768 ...
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