ZyXEL P-2602HW-D3A User Guide - Page 356

Example: Two Subnets

Page 356 highlights

P-2602H(W)(L)-DxA Series User's Guide Table 136 Alternative Subnet Mask Notation (continued) SUBNET MASK 255.255.255.240 255.255.255.248 255.255.255.252 SUBNET MASK "1" BITS /28 /29 /30 LAST OCTET BIT VALUE 1111 0000 1111 1000 1111 1100 DECIMAL 240 248 252 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. Table 137 Two Subnets Example IP/SUBNET MASK IP Address IP Address (Binary) Subnet Mask Subnet Mask (Binary) NETWORK NUMBER 192.168.1. 11000000.10101000.00000001. 255.255.255. 11111111.11111111.11111111. HOST ID 0 00000000 0 00000000 The first three octets of the address make up the network number (class "C"). To make two 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. Note: In the following charts, shaded/bolded last octet bit values indicate host ID bits "borrowed" to make 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. Table 138 Subnet 1 IP/SUBNET MASK IP Address IP Address (Binary) Subnet Mask Subnet Mask (Binary) 356 NETWORK NUMBER 192.168.1. 11000000.10101000.00000001. 255.255.255. 11111111.11111111.11111111. LAST OCTET BIT VALUE 0 00000000 128 10000000 Appendix D IP Addresses and Subnetting

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P-2602H(W)(L)-DxA Series User’s Guide
356
Appendix D IP Addresses and Subnetting
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”).
To make two 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.
Note:
In the following charts, shaded/bolded last octet bit values indicate host ID bits
“borrowed” to make 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.
255.255.255.240
/28
1111 0000
240
255.255.255.248
/29
1111 1000
248
255.255.255.252
/30
1111 1100
252
Table 136
Alternative Subnet Mask Notation (continued)
SUBNET MASK
SUBNET MASK “1” BITS
LAST OCTET BIT VALUE
DECIMAL
Table 137
Two Subnets Example
IP/SUBNET MASK
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
Table 138
Subnet 1
IP/SUBNET MASK
NETWORK NUMBER
LAST OCTET BIT
VALUE
IP Address
192.168.1.
0
IP Address (Binary)
11000000.10101000.00000001.
0
0000000
Subnet Mask
255.255.255.
128
Subnet Mask (Binary)
11111111.11111111.11111111.
1
0000000