ZyXEL Communications MWR102 manual Notation, Network Size, Maximum Host Numbers

24-bit mask	11111111	11111111	11111111	00000000	255.255.255.0
29-bit mask	11111111	11111111	11111111	11111000	255.255.255.248

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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:

Table 28 Maximum Host Numbers

SUBNET MASK		HOST ID SIZE				MAXIMUM NUMBER OF
						HOSTS
8 bits	255.0.0.0	24 bits	224		– 2	16777214
16 bits	255.255.0.0	16 bits	216		– 2	65534
24 bits	255.255.255.0	8 bits	28	– 2		254
29 bits	255.255.255.248	3 bits	23	– 2		6

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.

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