Appendix B IP Addresses and Subnetting
P-663H-51 User’s Guide
173
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 67
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 68
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 69
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
Summary of Contents for P-663H-51
Page 2: ......
Page 7: ...Safety Warnings P 663H 51 User s Guide 7 ...
Page 8: ...Safety Warnings P 663H 51 User s Guide 8 ...
Page 10: ...Contents Overview P 663H 51 User s Guide 10 ...
Page 20: ...List of Figures P 663H 51 User s Guide 20 ...
Page 23: ...23 PART I Introduction Introducing the ZyXEL Device 25 Introducing the Web Configurator 31 ...
Page 24: ...24 ...
Page 30: ...Chapter 1 Introducing the ZyXEL Device P 663H 51 User s Guide 30 ...
Page 36: ...Chapter 2 Introducing the Web Configurator P 663H 51 User s Guide 36 ...
Page 50: ...50 ...
Page 66: ...Chapter 5 WAN Setup P 663H 51 User s Guide 66 Figure 30 Advanced Setup WAN Add Summary MER ...
Page 108: ...Chapter 13 Dynamic DNS Setup P 663H 51 User s Guide 108 ...
Page 114: ...Chapter 15 Port Mapping P 663H 51 User s Guide 114 ...
Page 116: ...116 ...
Page 118: ...Chapter 16 Diagnostics P 663H 51 User s Guide 118 ...
Page 122: ...Chapter 17 Settings P 663H 51 User s Guide 122 ...
Page 126: ...Chapter 18 Logs P 663H 51 User s Guide 126 ...
Page 130: ...Chapter 19 SNMP P 663H 51 User s Guide 130 ...
Page 132: ...Chapter 20 Time P 663H 51 User s Guide 132 ...
Page 140: ...Chapter 23 Save Reboot and Logout P 663H 51 User s Guide 140 ...
Page 141: ...141 PART IV Troubleshooting and Specifications Troubleshooting 143 Product Specifications 147 ...
Page 142: ...142 ...
Page 152: ...Chapter 25 Product Specifications P 663H 51 User s Guide 152 ...
Page 154: ...154 ...
Page 188: ...Appendix D Common Services P 663H 51 User s Guide 188 ...
Page 196: ...Appendix F Legal Information P 663H 51 User s Guide 196 ...
Page 202: ...Appendix G Customer Support P 663H 51 User s Guide 202 ...