Subnet Mask Cheat Sheet for Network Admins
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 (also known as a prefix) sets the address range of usable IP addresses (octets made of host and network bits) within a network or subnet. Subnetting divides a larger network into smaller subnetworks. 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.
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.