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The TCP/IP Guide  9  TCP/IP Lower-Layer (Interface, Internet and Transport) Protocols (OSI Layers 2, 3 and 4)       9  TCP/IP Internet Layer (OSI Network Layer) Protocols            9  Internet Protocol (IP/IPv4, IPng/IPv6) and IP-Related Protocols (IP NAT, IPSec, Mobile IP)                 9  Internet Protocol Version 4 (IP, IPv4)                      9  IP Addressing                           9  IP Subnet Addressing ("Subnetting") Concepts

IP Subnet Identifiers, Subnet Addresses and Host Addresses 1 2 3 4 IP Variable Length Subnet Masking (VLSM)

Class C

Table 54: Subnetting Summary Table For Class C Networks

# of Subnet ID Bit	# of Host ID Bits	# of Subnets Per Network	# of Hosts Per Subnet	Subnet Mask (Binary / Dotted Decimal)		Subnet Mask (Slash/ CIDR Notation)	Subnet Address #N Formula (N=0, 1, … # of Subnets-1)
0 (Default)	8	1	254	11111111.11111111.11111111.00000000 255.255.255.0		/24	—
1	7	2	126	11111111.11111111.11111111.10000000 255.255.255.128		/25	x.y.z.N*128
2	6	4	62	11111111.11111111.11111111.11000000 255.255.255.192		/26	x.y.z.N*64
3	5	8	30	11111111.11111111.11111111.11100000 255.255.255.224		/27	x.y.z.N*32
4	4	16	14	11111111.11111111.11111111.11110000 255.255.255.240		/28	x.y.z.N*16
5	3	32	6	11111111.11111111.11111111.11111000 255.255.255.248		/29	x.y.z.N*8
6	2	64	2	11111111.11111111.11111111.11111100 255.255.255.252		/30	x.y.z.N*4

IP Subnet Identifiers, Subnet Addresses and Host Addresses 1 2 3 4 IP Variable Length Subnet Masking (VLSM)

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Version 3.0 - Version Date: September 20, 2005

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