Omega Vehicle Security zSeries manual Appendix CIP Netmask, Or Dotted Notation, Class a, Class B

Appendix CIP Netmask

IP Netmask or Subnet Mask is a 32-bit pattern of ones and zeros used to determine network portion of an IP address from the host portion of the IP address. Subnet mask is a network ID that is created by borrowing bits from host portion of IP address and using them as part of a network ID. The table below shows a default subnet mask for address Classes A, B, and C. Each bit that is set to "1" in the subnet mask corresponds to the bit in the IP address that is to be used as the network ID. Each bit that is set to "0" in the subnet mask corresponds to a bit in the IP address that is to be used as the host ID.

	Address Class		Mask Binary Value				Mask Decimal Value
		11111111	00000000	00000000	00000000		or Dotted Notation
	Class A						255.0.0.0
	Class B	11111111	11111111	00000000	00000000		255.255.0.0
	Class C	11111111	11111111	11111111	00000000		255.255.255.0
If your network requires more network ID’s, you can extend the default subnet mask to
include additional bits from the host ID. This allows for additional network ID’s within the
network. The table below shows some examples of subnet masks and bits moved from
the hosts ID to create a new subnet.
	Mask Dotted Notation			Mask Binary				Mask Bits
			11111111	Class A
	255.0.0.0 (Default)			00000000	00000000	00000000			0
255.192.0.0			11111111	11000000	00000000	00000000			2
255.224.0.0			11111111	11100000	00000000	00000000			3
255.240.0.0			11111111	11110000	00000000	00000000			4
255.248.0.0			11111111	11111000	00000000	00000000			5
255.252.0.0			11111111	11111100	00000000	00000000			6
255.254.0.0			11111111	11111110	00000000	00000000			7
255.255.0.0			11111111	11111111	00000000	00000000			8
255.255.128.0			11111111	11111111	10000000	00000000			9
255.255.192.0.0			11111111	11111111	11000000	00000000			10
	……………		.. .. . .. . . . . . . . . . .. . .. .. . .. . . . . . .						.
255.255.255.252			11111111	11111111	11111111	11111100			22
				Class B
	255.255.0.0 (Default)		11111111	11111111	00000000	00000000			0
255.255.192.0			11111111	11111111	11000000	00000000			2
	……………		. .. . .. .. . . . . . . . . .. .. .. . . .. . . . . . .						.
255.255.255.252			11111111	11111111	11111111	11111100			14
	255.255.255.0 (Default)		11111111	Class C					0
				11111111	11111111	00000000
255.255.255.192			11111111	11111111	11111111	11000000			2
	………………….		. .. . .. .. . . . . . . . . .. .. .. . . .. . . . . . .						.
255.255.255.254			11111111	11111111	11111111	11111100			6
To determine the number of valid hosts ID’s remaining after subnetting, use the following
equation: 2n – 2, where n is the number of octet digits left after the subnet mask.

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