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Subnet Mask Cheat Sheet for Network Admins

Abstract

Subnet masks set the address ranges of usable IP addresses within a network. Use this page for your Access Server network.

IT professionals (developers, network engineers) need easy access to subnet mask values and their meanings, so OpenVPN prepared this easy-to-use cheat sheet.

The subnet mask (aka prefix) sets the address range of usable IP addresses (octets made of host and network bits) within a network or subnet. Subnetting breaks out a smaller network from the main network. The 32-bit combination distinguishes two parts of an address: 1) one that refers to the subnet and 2) one that refers to the host. Numbers and decimals make up a subnet mask.

Additional information on networking concepts is available here and includes:

  • IPv4 addresses, IPv6 addresses, and private networks.

  • Cheat sheet for CIDR notation (the number of bits available to the IP address.

See also RFC 1878.

Addresses

Hosts

Netmask

Amount of a Class C

/30

4

2

255.255.255.252

1/64

/29

8

6

255.255.255.248

1/32

/28

16

14

255.255.255.240

1/16

/27

32

30

255.255.255.224

1/8

/26

64

62

255.255.255.192

1/4

/25

128

126

255.255.255.128

1/2

/24

256

254

255.255.255.0

1

/23

512

510

255.255.254.0

2

/22

1024

1022

255.255.252.0

4

/21

2048

2046

255.255.248.0

8

/20

4096

4094

255.255.240.0

16

/19

8192

8190

255.255.224.0

32

/18

16384

16382

255.255.192.0

64

/17

32768

32766

255.255.128.0

128

/16

65536

65534

255.255.0.0

256

Note

In 1993, Classless Inter-Domain Routing replaced classful IP addressing. CIDR uses five address classes based on the four lead address bits.

  • Class A, B, and C: Provide unicast addresses for three network sizes.

  • Class D: For multicast networking.

  • Class E: Reserved for future and/or experimental use.

Network #

IP Range

Broadcast

.0

.1-.126

.127

.128

.129-.254

.255

Network #

IP Range

Broadcast

.0

.1-.62

.63

.64

.65-.126

.127

.128

.129-.190

.191

.192

.193-.254

.255

Network #

IP Range

Broadcast

.0

.1-.30

.31

.32

.33-.62

.63

.64

.65-.94

.95

.96

.97-.126

.127

.128

.129-.158

.159

.160

.161-.190

.191

.192

.193-.222

.223

.224

.225-.254

.255

Network #

IP Range

Broadcast

.0

.1-.14

.15

.16

.17-.30

.31

.32

.33-.46

.47

.48

.49-.62

.63

.64

.65-.78

.79

.80

.81-.94

.95

.96

.97-.110

.111

.112

.113-.126

.127

.128

.129-.142

.143

.144

.145-.158

.159

.160

.161-.174

.175

.176

.177-.190

.191

.192

.193-.206

.207

.208

.209-.222

.223

.224

.225-.238

.239

.240

.241-.254

.255

Network #

IP Range

Broadcast

.0

.1-.6

.7

.8

.9-.14

.15

.16

.17-.22

.23

.24

.25-.30

.31

.32

.33-.38

.39

.40

.41-.46

.47

.48

.49-.54

.55

.56

.57-.62

.63

.64

.65-.70

.71

.72

.73-.78

.79

.80

.81-.86

.87

.88

.89-.94

.95

.96

.97-.102

.103

.104

.105-.110

.111

.112

.113-.118

.119

.120

.121-.126

.127

.128

.129-.134

.135

.136

.137-.142

.143

.144

.145-.150

.151

.152

.153-.158

.159

.160

.161-.166

.167

.168

.169-.174

.175

.176

.177-.182

.183

.184

.185-.190

.191

.192

.193-.198

.199

.200

.201-.206

.207

.208

.209-.214

.215

.216

.217-.222

.223

.224

.225-.230

.231

.232

.233-.238

.239

.240

.241-.246

.247

.248

.249-.254

.255

Network #

IP Range

Broadcast

.0

.1-.2

.3

.4

.5-.6

.7

.8

.9-.10

.11

.12

.13-.14

.15

.16

.17-.18

.19

.20

.21-.22

.23

.24

.25-.26

.27

.28

.29-.30

.31

.32

.33-.34

.35

.36

.37-.38

.39

.40

.41-.42

.43

.44

.45-.46

.47

.48

.49-.50

.51

.52

.53-.54

.55

.56

.57-.58

.59

.60

.61-.62

.63

.64

.65-.66

.67

.68

.69-.70

.71

.72

.73-.74

.75

.76

.77-.78

.79

.80

.81-.82

.83

.84

.85-.86

.87

.88

.89-.90

.91

.92

.93-.94

.95

.96

.97-.98

.99

.100

.101-.102

.103

.104

.105-.106

.107

.108

.109-.110

.111

.112

.113-.114

.115

.116

.117-.118

.119

.120

.121-.122

.123

.124

.125-.126

.127

.128

.129-.130

.131

.132

.133-.134

.135

.136

.137-.138

.139

.140

.141-.142

.143

.144

.145-.146

.147

.148

.149-.150

.151

.152

.153-.154

.155

.156

.157-.158

.159

.160

.161-.162

.163

.164

.165-.166

.167

.168

.169-.170

.171

.172

.173-.174

.175

.176

.177-.178

.179

.180

.181-.182

.183

.184

.185-.186

.187

.188

.189-.190

.191

.192

.193-.194

.195

.196

.197-.198

.199

.200

.201-.202

.203

.204

.205-.206

.207

.208

.209-.210

.211

.212

.213-.214

.215

.216

.217-.218

.219

.220

.221-.222

.223

.224

.225-.226

.227

.228

.229-.230

.231

.232

.233-.234

.235

.236

.237-.238

.239

.240

.241-.242

.243

.244

.245-.246

.247

.248

.249-.250

.251

.252

.253-.254

.255

  • The loopback network in an IPv4 subnet is 127.0.0.0 with a subnet mask of 255.0.0.0.

  • A localhost communication port connects to the originating server so a network connection can “loop back” on itself.

  • Class C networks use a default subnet mask of 255.255.255.0 and have 192-223 as their first octet.

  • The wildcard mask for a Host is always 0.0.0.0.

  • A broadcast address, the highest value in the address format, enables transmission to every node in a local network.

  • A Variable Length Subnet Mask (VLSM) uses more than one mask in a network to increase subnet usability.