ZyXEL Communications G-1000 Example Two Subnets, Subnet Mask Ip Address, SUBNET MASK “1” BITS

Models: G-1000

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SUBNET MASK IP ADDRESS

G-1000 User’s Guide

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 mask 255.255.255.128.

The following table shows all possible subnet masks for a class “C” address using both notations.

Table 73 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

 

 

 

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 74 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

 

 

 

The first three octets of the address make up the network number (class “C”). You want to have two separate networks.

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IP Subnetting

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ZyXEL Communications G-1000 manual Example Two Subnets, Subnet Mask Ip Address, SUBNET MASK “1” BITS, Last Octet Bit Value