ZyXEL Communications wireless n gigbit router zyxel manual Notation, 332, Maximum Host Numbers

Appendix B IP Addresses and Subnetting

As these two IP addresses cannot be used for individual hosts, calculate the maximum number of possible hosts in a network as follows:

Table 124 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	255.255.255.2	3 bits	23 – 2	6
	48

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 125 Alternative Subnet Mask Notation

SUBNET	ALTERNATIVE	LAST OCTET	LAST OCTET
MASK	NOTATION	(BINARY)	(DECIMAL)
255.255.255.0	/24	0000 0000	0
255.255.255.12	/25	1000 0000	128
8
255.255.255.19	/26	1100 0000	192
2
255.255.255.22	/27	1110 0000	224
4
255.255.255.24	/28	1111 0000	240
0
255.255.255.24	/29	1111 1000	248
8
255.255.255.25	/30	1111 1100	252
2

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NBG-460N User’s Guide