Speed and call quality testMy IP addressIP subnet calculatorDNS reportWhoIs lookupRemote support

Internet and network

Speed and call quality testTest delay, jitter and speed, with a focus on phone calls.My IP addressYour public IPv4 and IPv6 addresses, provider and address range.WhoIs lookupWho owns a domain or IP address, when it expires, and its DNS.DNS reportEvery DNS record for a domain, with email setup checked.IP subnet calculatorWork out a network's range, mask and hosts, and split it into subnets.

Computers and devices

Update checkIs this computer, phone and browser up to date? With links to update.Camera and mic testCheck your webcam and microphone before a call.Test print pagePrint an A4 page to check a printer: edges, text, line art and colours.

Make and print

Clean textStrip hidden characters, smart quotes and odd spaces from pasted text.QR code makerMake a QR code for a link, contact or message. Nothing leaves your browser.Wi-Fi QR posterPrint an A4 poster that lets guests join your Wi-Fi by scanning.

Surftec support

Remote supportLet a Surftec engineer connect to your computer to help you.All workingA full-screen confirmation that everything is up and running.

Surftec

Surftec websiteServices, news and how to contact Surftec
Cloud Tools
Guest
GuestNot signed in

Surftec customers will be recognised automatically when they use these tools from their office network.

Customer sign-in is coming soon.

IP subnet calculator

Type an address with its prefix or mask to see the network, its usable range and masks. Split it into smaller subnets, or look up any prefix in the reference tables.

Network224.167.72.0/21
Usable hosts2,046
Subnet mask255.255.248.0
Addresses2,048
Network address
224.167.72.0
Broadcast address
224.167.79.255
First usable
224.167.72.1
Last usable
224.167.79.254
Usable hosts
2,046 (2,048 less the network and broadcast addresses)
Subnet mask
255.255.248.0
Wildcard mask
0.0.7.255 (Cisco ACLs, OSPF)
Prefix length
/21
Type
Multicast 224.0.0.0/4
One-to-many traffic, such as IPTV and routing protocols
Old class
D (multicast)
As numbers
Hex E0A74800 · Integer 3769059328 to 3769061375
Reverse DNS zones
72.167.224.in-addr.arpa
73.167.224.in-addr.arpa
74.167.224.in-addr.arpa
75.167.224.in-addr.arpa
76.167.224.in-addr.arpa
77.167.224.in-addr.arpa
78.167.224.in-addr.arpa
79.167.224.in-addr.arpa
/21 is not on a 8-bit boundary, so it takes 8 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11100000.10100111.01001000.00000000224.167.72.0
Subnet mask11111111.11111111.11111000.00000000255.255.248.0
Network11100000.10100111.01001000.00000000224.167.72.0
Broadcast11100000.10100111.01001111.11111111224.167.79.255
Split into smaller subnets/32
/22 (2)/23 (4)/24 (8)/25 (16)/26 (32)/27 (64)/28 (128)/29 (256)/30 (512)/31 (1,024)/32 (2,048)

224.167.72.0/21 makes 2,048 subnets of /32; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1224.167.72.0/32224.167.72.0 to 224.167.72.0—1
2224.167.72.1/32224.167.72.1 to 224.167.72.1—1
3224.167.72.2/32224.167.72.2 to 224.167.72.2—1
4224.167.72.3/32224.167.72.3 to 224.167.72.3—1
5224.167.72.4/32224.167.72.4 to 224.167.72.4—1
6224.167.72.5/32224.167.72.5 to 224.167.72.5—1
7224.167.72.6/32224.167.72.6 to 224.167.72.6—1
8224.167.72.7/32224.167.72.7 to 224.167.72.7—1
9224.167.72.8/32224.167.72.8 to 224.167.72.8—1
10224.167.72.9/32224.167.72.9 to 224.167.72.9—1
11224.167.72.10/32224.167.72.10 to 224.167.72.10—1
12224.167.72.11/32224.167.72.11 to 224.167.72.11—1
13224.167.72.12/32224.167.72.12 to 224.167.72.12—1
14224.167.72.13/32224.167.72.13 to 224.167.72.13—1
15224.167.72.14/32224.167.72.14 to 224.167.72.14—1
16224.167.72.15/32224.167.72.15 to 224.167.72.15—1
17224.167.72.16/32224.167.72.16 to 224.167.72.16—1
18224.167.72.17/32224.167.72.17 to 224.167.72.17—1
19224.167.72.18/32224.167.72.18 to 224.167.72.18—1
20224.167.72.19/32224.167.72.19 to 224.167.72.19—1
21224.167.72.20/32224.167.72.20 to 224.167.72.20—1
22224.167.72.21/32224.167.72.21 to 224.167.72.21—1
23224.167.72.22/32224.167.72.22 to 224.167.72.22—1
24224.167.72.23/32224.167.72.23 to 224.167.72.23—1
25224.167.72.24/32224.167.72.24 to 224.167.72.24—1
26224.167.72.25/32224.167.72.25 to 224.167.72.25—1
27224.167.72.26/32224.167.72.26 to 224.167.72.26—1
28224.167.72.27/32224.167.72.27 to 224.167.72.27—1
29224.167.72.28/32224.167.72.28 to 224.167.72.28—1
30224.167.72.29/32224.167.72.29 to 224.167.72.29—1
31224.167.72.30/32224.167.72.30 to 224.167.72.30—1
32224.167.72.31/32224.167.72.31 to 224.167.72.31—1
33224.167.72.32/32224.167.72.32 to 224.167.72.32—1
34224.167.72.33/32224.167.72.33 to 224.167.72.33—1
35224.167.72.34/32224.167.72.34 to 224.167.72.34—1
36224.167.72.35/32224.167.72.35 to 224.167.72.35—1
37224.167.72.36/32224.167.72.36 to 224.167.72.36—1
38224.167.72.37/32224.167.72.37 to 224.167.72.37—1
39224.167.72.38/32224.167.72.38 to 224.167.72.38—1
40224.167.72.39/32224.167.72.39 to 224.167.72.39—1
41224.167.72.40/32224.167.72.40 to 224.167.72.40—1
42224.167.72.41/32224.167.72.41 to 224.167.72.41—1
43224.167.72.42/32224.167.72.42 to 224.167.72.42—1
44224.167.72.43/32224.167.72.43 to 224.167.72.43—1
45224.167.72.44/32224.167.72.44 to 224.167.72.44—1
46224.167.72.45/32224.167.72.45 to 224.167.72.45—1
47224.167.72.46/32224.167.72.46 to 224.167.72.46—1
48224.167.72.47/32224.167.72.47 to 224.167.72.47—1
49224.167.72.48/32224.167.72.48 to 224.167.72.48—1
50224.167.72.49/32224.167.72.49 to 224.167.72.49—1
51224.167.72.50/32224.167.72.50 to 224.167.72.50—1
52224.167.72.51/32224.167.72.51 to 224.167.72.51—1
53224.167.72.52/32224.167.72.52 to 224.167.72.52—1
54224.167.72.53/32224.167.72.53 to 224.167.72.53—1
55224.167.72.54/32224.167.72.54 to 224.167.72.54—1
56224.167.72.55/32224.167.72.55 to 224.167.72.55—1
57224.167.72.56/32224.167.72.56 to 224.167.72.56—1
58224.167.72.57/32224.167.72.57 to 224.167.72.57—1
59224.167.72.58/32224.167.72.58 to 224.167.72.58—1
60224.167.72.59/32224.167.72.59 to 224.167.72.59—1
61224.167.72.60/32224.167.72.60 to 224.167.72.60—1
62224.167.72.61/32224.167.72.61 to 224.167.72.61—1
63224.167.72.62/32224.167.72.62 to 224.167.72.62—1
64224.167.72.63/32224.167.72.63 to 224.167.72.63—1
65224.167.72.64/32224.167.72.64 to 224.167.72.64—1
66224.167.72.65/32224.167.72.65 to 224.167.72.65—1
67224.167.72.66/32224.167.72.66 to 224.167.72.66—1
68224.167.72.67/32224.167.72.67 to 224.167.72.67—1
69224.167.72.68/32224.167.72.68 to 224.167.72.68—1
70224.167.72.69/32224.167.72.69 to 224.167.72.69—1
71224.167.72.70/32224.167.72.70 to 224.167.72.70—1
72224.167.72.71/32224.167.72.71 to 224.167.72.71—1
73224.167.72.72/32224.167.72.72 to 224.167.72.72—1
74224.167.72.73/32224.167.72.73 to 224.167.72.73—1
75224.167.72.74/32224.167.72.74 to 224.167.72.74—1
76224.167.72.75/32224.167.72.75 to 224.167.72.75—1
77224.167.72.76/32224.167.72.76 to 224.167.72.76—1
78224.167.72.77/32224.167.72.77 to 224.167.72.77—1
79224.167.72.78/32224.167.72.78 to 224.167.72.78—1
80224.167.72.79/32224.167.72.79 to 224.167.72.79—1
81224.167.72.80/32224.167.72.80 to 224.167.72.80—1
82224.167.72.81/32224.167.72.81 to 224.167.72.81—1
83224.167.72.82/32224.167.72.82 to 224.167.72.82—1
84224.167.72.83/32224.167.72.83 to 224.167.72.83—1
85224.167.72.84/32224.167.72.84 to 224.167.72.84—1
86224.167.72.85/32224.167.72.85 to 224.167.72.85—1
87224.167.72.86/32224.167.72.86 to 224.167.72.86—1
88224.167.72.87/32224.167.72.87 to 224.167.72.87—1
89224.167.72.88/32224.167.72.88 to 224.167.72.88—1
90224.167.72.89/32224.167.72.89 to 224.167.72.89—1
91224.167.72.90/32224.167.72.90 to 224.167.72.90—1
92224.167.72.91/32224.167.72.91 to 224.167.72.91—1
93224.167.72.92/32224.167.72.92 to 224.167.72.92—1
94224.167.72.93/32224.167.72.93 to 224.167.72.93—1
95224.167.72.94/32224.167.72.94 to 224.167.72.94—1
96224.167.72.95/32224.167.72.95 to 224.167.72.95—1
97224.167.72.96/32224.167.72.96 to 224.167.72.96—1
98224.167.72.97/32224.167.72.97 to 224.167.72.97—1
99224.167.72.98/32224.167.72.98 to 224.167.72.98—1
100224.167.72.99/32224.167.72.99 to 224.167.72.99—1
101224.167.72.100/32224.167.72.100 to 224.167.72.100—1
102224.167.72.101/32224.167.72.101 to 224.167.72.101—1
103224.167.72.102/32224.167.72.102 to 224.167.72.102—1
104224.167.72.103/32224.167.72.103 to 224.167.72.103—1
105224.167.72.104/32224.167.72.104 to 224.167.72.104—1
106224.167.72.105/32224.167.72.105 to 224.167.72.105—1
107224.167.72.106/32224.167.72.106 to 224.167.72.106—1
108224.167.72.107/32224.167.72.107 to 224.167.72.107—1
109224.167.72.108/32224.167.72.108 to 224.167.72.108—1
110224.167.72.109/32224.167.72.109 to 224.167.72.109—1
111224.167.72.110/32224.167.72.110 to 224.167.72.110—1
112224.167.72.111/32224.167.72.111 to 224.167.72.111—1
113224.167.72.112/32224.167.72.112 to 224.167.72.112—1
114224.167.72.113/32224.167.72.113 to 224.167.72.113—1
115224.167.72.114/32224.167.72.114 to 224.167.72.114—1
116224.167.72.115/32224.167.72.115 to 224.167.72.115—1
117224.167.72.116/32224.167.72.116 to 224.167.72.116—1
118224.167.72.117/32224.167.72.117 to 224.167.72.117—1
119224.167.72.118/32224.167.72.118 to 224.167.72.118—1
120224.167.72.119/32224.167.72.119 to 224.167.72.119—1
121224.167.72.120/32224.167.72.120 to 224.167.72.120—1
122224.167.72.121/32224.167.72.121 to 224.167.72.121—1
123224.167.72.122/32224.167.72.122 to 224.167.72.122—1
124224.167.72.123/32224.167.72.123 to 224.167.72.123—1
125224.167.72.124/32224.167.72.124 to 224.167.72.124—1
126224.167.72.125/32224.167.72.125 to 224.167.72.125—1
127224.167.72.126/32224.167.72.126 to 224.167.72.126—1
128224.167.72.127/32224.167.72.127 to 224.167.72.127—1
129224.167.72.128/32224.167.72.128 to 224.167.72.128—1
130224.167.72.129/32224.167.72.129 to 224.167.72.129—1
131224.167.72.130/32224.167.72.130 to 224.167.72.130—1
132224.167.72.131/32224.167.72.131 to 224.167.72.131—1
133224.167.72.132/32224.167.72.132 to 224.167.72.132—1
134224.167.72.133/32224.167.72.133 to 224.167.72.133—1
135224.167.72.134/32224.167.72.134 to 224.167.72.134—1
136224.167.72.135/32224.167.72.135 to 224.167.72.135—1
137224.167.72.136/32224.167.72.136 to 224.167.72.136—1
138224.167.72.137/32224.167.72.137 to 224.167.72.137—1
139224.167.72.138/32224.167.72.138 to 224.167.72.138—1
140224.167.72.139/32224.167.72.139 to 224.167.72.139—1
141224.167.72.140/32224.167.72.140 to 224.167.72.140—1
142224.167.72.141/32224.167.72.141 to 224.167.72.141—1
143224.167.72.142/32224.167.72.142 to 224.167.72.142—1
144224.167.72.143/32224.167.72.143 to 224.167.72.143—1
145224.167.72.144/32224.167.72.144 to 224.167.72.144—1
146224.167.72.145/32224.167.72.145 to 224.167.72.145—1
147224.167.72.146/32224.167.72.146 to 224.167.72.146—1
148224.167.72.147/32224.167.72.147 to 224.167.72.147—1
149224.167.72.148/32224.167.72.148 to 224.167.72.148—1
150224.167.72.149/32224.167.72.149 to 224.167.72.149—1
151224.167.72.150/32224.167.72.150 to 224.167.72.150—1
152224.167.72.151/32224.167.72.151 to 224.167.72.151—1
153224.167.72.152/32224.167.72.152 to 224.167.72.152—1
154224.167.72.153/32224.167.72.153 to 224.167.72.153—1
155224.167.72.154/32224.167.72.154 to 224.167.72.154—1
156224.167.72.155/32224.167.72.155 to 224.167.72.155—1
157224.167.72.156/32224.167.72.156 to 224.167.72.156—1
158224.167.72.157/32224.167.72.157 to 224.167.72.157—1
159224.167.72.158/32224.167.72.158 to 224.167.72.158—1
160224.167.72.159/32224.167.72.159 to 224.167.72.159—1
161224.167.72.160/32224.167.72.160 to 224.167.72.160—1
162224.167.72.161/32224.167.72.161 to 224.167.72.161—1
163224.167.72.162/32224.167.72.162 to 224.167.72.162—1
164224.167.72.163/32224.167.72.163 to 224.167.72.163—1
165224.167.72.164/32224.167.72.164 to 224.167.72.164—1
166224.167.72.165/32224.167.72.165 to 224.167.72.165—1
167224.167.72.166/32224.167.72.166 to 224.167.72.166—1
168224.167.72.167/32224.167.72.167 to 224.167.72.167—1
169224.167.72.168/32224.167.72.168 to 224.167.72.168—1
170224.167.72.169/32224.167.72.169 to 224.167.72.169—1
171224.167.72.170/32224.167.72.170 to 224.167.72.170—1
172224.167.72.171/32224.167.72.171 to 224.167.72.171—1
173224.167.72.172/32224.167.72.172 to 224.167.72.172—1
174224.167.72.173/32224.167.72.173 to 224.167.72.173—1
175224.167.72.174/32224.167.72.174 to 224.167.72.174—1
176224.167.72.175/32224.167.72.175 to 224.167.72.175—1
177224.167.72.176/32224.167.72.176 to 224.167.72.176—1
178224.167.72.177/32224.167.72.177 to 224.167.72.177—1
179224.167.72.178/32224.167.72.178 to 224.167.72.178—1
180224.167.72.179/32224.167.72.179 to 224.167.72.179—1
181224.167.72.180/32224.167.72.180 to 224.167.72.180—1
182224.167.72.181/32224.167.72.181 to 224.167.72.181—1
183224.167.72.182/32224.167.72.182 to 224.167.72.182—1
184224.167.72.183/32224.167.72.183 to 224.167.72.183—1
185224.167.72.184/32224.167.72.184 to 224.167.72.184—1
186224.167.72.185/32224.167.72.185 to 224.167.72.185—1
187224.167.72.186/32224.167.72.186 to 224.167.72.186—1
188224.167.72.187/32224.167.72.187 to 224.167.72.187—1
189224.167.72.188/32224.167.72.188 to 224.167.72.188—1
190224.167.72.189/32224.167.72.189 to 224.167.72.189—1
191224.167.72.190/32224.167.72.190 to 224.167.72.190—1
192224.167.72.191/32224.167.72.191 to 224.167.72.191—1
193224.167.72.192/32224.167.72.192 to 224.167.72.192—1
194224.167.72.193/32224.167.72.193 to 224.167.72.193—1
195224.167.72.194/32224.167.72.194 to 224.167.72.194—1
196224.167.72.195/32224.167.72.195 to 224.167.72.195—1
197224.167.72.196/32224.167.72.196 to 224.167.72.196—1
198224.167.72.197/32224.167.72.197 to 224.167.72.197—1
199224.167.72.198/32224.167.72.198 to 224.167.72.198—1
200224.167.72.199/32224.167.72.199 to 224.167.72.199—1
201224.167.72.200/32224.167.72.200 to 224.167.72.200—1
202224.167.72.201/32224.167.72.201 to 224.167.72.201—1
203224.167.72.202/32224.167.72.202 to 224.167.72.202—1
204224.167.72.203/32224.167.72.203 to 224.167.72.203—1
205224.167.72.204/32224.167.72.204 to 224.167.72.204—1
206224.167.72.205/32224.167.72.205 to 224.167.72.205—1
207224.167.72.206/32224.167.72.206 to 224.167.72.206—1
208224.167.72.207/32224.167.72.207 to 224.167.72.207—1
209224.167.72.208/32224.167.72.208 to 224.167.72.208—1
210224.167.72.209/32224.167.72.209 to 224.167.72.209—1
211224.167.72.210/32224.167.72.210 to 224.167.72.210—1
212224.167.72.211/32224.167.72.211 to 224.167.72.211—1
213224.167.72.212/32224.167.72.212 to 224.167.72.212—1
214224.167.72.213/32224.167.72.213 to 224.167.72.213—1
215224.167.72.214/32224.167.72.214 to 224.167.72.214—1
216224.167.72.215/32224.167.72.215 to 224.167.72.215—1
217224.167.72.216/32224.167.72.216 to 224.167.72.216—1
218224.167.72.217/32224.167.72.217 to 224.167.72.217—1
219224.167.72.218/32224.167.72.218 to 224.167.72.218—1
220224.167.72.219/32224.167.72.219 to 224.167.72.219—1
221224.167.72.220/32224.167.72.220 to 224.167.72.220—1
222224.167.72.221/32224.167.72.221 to 224.167.72.221—1
223224.167.72.222/32224.167.72.222 to 224.167.72.222—1
224224.167.72.223/32224.167.72.223 to 224.167.72.223—1
225224.167.72.224/32224.167.72.224 to 224.167.72.224—1
226224.167.72.225/32224.167.72.225 to 224.167.72.225—1
227224.167.72.226/32224.167.72.226 to 224.167.72.226—1
228224.167.72.227/32224.167.72.227 to 224.167.72.227—1
229224.167.72.228/32224.167.72.228 to 224.167.72.228—1
230224.167.72.229/32224.167.72.229 to 224.167.72.229—1
231224.167.72.230/32224.167.72.230 to 224.167.72.230—1
232224.167.72.231/32224.167.72.231 to 224.167.72.231—1
233224.167.72.232/32224.167.72.232 to 224.167.72.232—1
234224.167.72.233/32224.167.72.233 to 224.167.72.233—1
235224.167.72.234/32224.167.72.234 to 224.167.72.234—1
236224.167.72.235/32224.167.72.235 to 224.167.72.235—1
237224.167.72.236/32224.167.72.236 to 224.167.72.236—1
238224.167.72.237/32224.167.72.237 to 224.167.72.237—1
239224.167.72.238/32224.167.72.238 to 224.167.72.238—1
240224.167.72.239/32224.167.72.239 to 224.167.72.239—1
241224.167.72.240/32224.167.72.240 to 224.167.72.240—1
242224.167.72.241/32224.167.72.241 to 224.167.72.241—1
243224.167.72.242/32224.167.72.242 to 224.167.72.242—1
244224.167.72.243/32224.167.72.243 to 224.167.72.243—1
245224.167.72.244/32224.167.72.244 to 224.167.72.244—1
246224.167.72.245/32224.167.72.245 to 224.167.72.245—1
247224.167.72.246/32224.167.72.246 to 224.167.72.246—1
248224.167.72.247/32224.167.72.247 to 224.167.72.247—1
249224.167.72.248/32224.167.72.248 to 224.167.72.248—1
250224.167.72.249/32224.167.72.249 to 224.167.72.249—1
251224.167.72.250/32224.167.72.250 to 224.167.72.250—1
252224.167.72.251/32224.167.72.251 to 224.167.72.251—1
253224.167.72.252/32224.167.72.252 to 224.167.72.252—1
254224.167.72.253/32224.167.72.253 to 224.167.72.253—1
255224.167.72.254/32224.167.72.254 to 224.167.72.254—1
256224.167.72.255/32224.167.72.255 to 224.167.72.255—1

IPv4 CIDR reference (/0 to /32)

IPv4 prefix lengths
PrefixSubnet maskWildcardAddressesUsable hostsSizeTypical use
/00.0.0.0255.255.255.2554,294,967,2964,294,967,29416,777,216 × /24
/1128.0.0.0127.255.255.2552,147,483,6482,147,483,6468,388,608 × /24
/2192.0.0.063.255.255.2551,073,741,8241,073,741,8224,194,304 × /24
/3224.0.0.031.255.255.255536,870,912536,870,9102,097,152 × /24
/4240.0.0.015.255.255.255268,435,456268,435,4541,048,576 × /24
/5248.0.0.07.255.255.255134,217,728134,217,726524,288 × /24
/6252.0.0.03.255.255.25567,108,86467,108,862262,144 × /24
/7254.0.0.01.255.255.25533,554,43233,554,430131,072 × /24
/8255.0.0.00.255.255.25516,777,21616,777,21465,536 × /24Old class A; 10.0.0.0/8
/9255.128.0.00.127.255.2558,388,6088,388,60632,768 × /24
/10255.192.0.00.63.255.2554,194,3044,194,30216,384 × /24
/11255.224.0.00.31.255.2552,097,1522,097,1508,192 × /24
/12255.240.0.00.15.255.2551,048,5761,048,5744,096 × /24172.16.0.0/12
/13255.248.0.00.7.255.255524,288524,2862,048 × /24
/14255.252.0.00.3.255.255262,144262,1421,024 × /24
/15255.254.0.00.1.255.255131,072131,070512 × /24
/16255.255.0.00.0.255.25565,53665,534256 × /24Old class B; 192.168.0.0/16
/17255.255.128.00.0.127.25532,76832,766128 × /24
/18255.255.192.00.0.63.25516,38416,38264 × /24
/19255.255.224.00.0.31.2558,1928,19032 × /24
/20255.255.240.00.0.15.2554,0964,09416 × /24
/21255.255.248.00.0.7.2552,0482,0468 × /24
/22255.255.252.00.0.3.2551,0241,0224 × /24Large office or guest Wi-Fi (1,022 hosts)
/23255.255.254.00.0.1.2555125102 × /24Larger office LAN (510 hosts)
/24255.255.255.00.0.0.2552562541 × /24Typical office LAN (old class C)
/25255.255.255.1280.0.0.1271281261/2 of a /24Smaller LAN or VLAN
/26255.255.255.1920.0.0.6364621/4 of a /24Smaller LAN or VLAN
/27255.255.255.2240.0.0.3132301/8 of a /24Small VLAN, phones, cameras
/28255.255.255.2400.0.0.1516141/16 of a /24Small VLAN, phones, cameras
/29255.255.255.2480.0.0.7861/32 of a /24Small fixed public block (5 usable)
/30255.255.255.2520.0.0.3421/64 of a /24Point-to-point (old style)
/31255.255.255.2540.0.0.1221/128 of a /24Point-to-point link (RFC 3021)
/32255.255.255.2550.0.0.0111/256 of a /24One host

IPv6 prefix reference

IPv6 prefix lengths
PrefixAddresses/64 LANs/48 sitesNibbleTypical use
/342,535,295,865,117,307,932,921,825,928,971,026,432 (2^125)2,305,843,009,213,693,95235,184,372,088,832NoAll global unicast (2000::/3)
/165,192,296,858,534,827,628,530,496,329,220,096 (2^112)281,474,976,710,6564,294,967,296Yes
/20324,518,553,658,426,726,783,156,020,576,256 (2^108)17,592,186,044,416268,435,456YesLarge provider allocation (RIPE minimum for some)
/29633,825,300,114,114,700,748,351,602,688 (2^99)34,359,738,368524,288NoRIPE allocation to a provider (often)
/3279,228,162,514,264,337,593,543,950,336 (2^96)4,294,967,29665,536YesProvider allocation (RIPE default)
/364,951,760,157,141,521,099,596,496,896 (2^92)268,435,4564,096Yes
/40309,485,009,821,345,068,724,781,056 (2^88)16,777,216256Yes
/4419,342,813,113,834,066,795,298,816 (2^84)1,048,57616Yes
/481,208,925,819,614,629,174,706,176 (2^80)65,5361YesOne site or organisation (RIPE PI / assignment)
/5275,557,863,725,914,323,419,136 (2^76)4,096Yes
/564,722,366,482,869,645,213,696 (2^72)256YesSmall site or home (common provider assignment)
/60295,147,905,179,352,825,856 (2^68)16YesSome home broadband (16 LANs)
/6418,446,744,073,709,551,616 (2^64)1YesOne LAN or VLAN (needed for SLAAC)
/7272,057,594,037,927,936 (2^56)1/256 of a /64Yes
/80281,474,976,710,656 (2^48)1/65,536 of a /64Yes
/964,294,967,2961/4,294,967,296 of a /64YesEmbeds an IPv4 address (NAT64)
/11265,5361/281,474,976,710,656 of a /64Yes
/1202561/72,057,594,037,927,936 of a /64Yes
/124161/1,152,921,504,606,846,976 of a /64Yes
/12641/4,611,686,018,427,387,904 of a /64No
/12721/9,223,372,036,854,775,808 of a /64NoPoint-to-point link (RFC 6164)
/12811/18,446,744,073,709,551,616 of a /64YesOne host or loopback

Private and special ranges

IPv4

Special-purpose ranges
RangeNameWhat it is
255.255.255.255/32Limited broadcastEvery host on the local network
0.0.0.0/8This networkNot routed; 0.0.0.0 means "any address" in settings
10.0.0.0/8Private (RFC 1918)Office and home networks; not routed on the internet
100.64.0.0/10Shared address space (CGNAT)Used by providers behind carrier-grade NAT (RFC 6598)
127.0.0.0/8LoopbackThis computer
169.254.0.0/16Link-local (APIPA)Self-assigned when no DHCP server answers
172.16.0.0/12Private (RFC 1918)Office and home networks; not routed on the internet
192.0.0.0/24IETF protocol assignmentsSpecial uses such as DS-Lite
192.0.2.0/24Documentation (TEST-NET-1)For examples; never used on a network
192.88.99.0/246to4 relay (deprecated)Formerly anycast for 6to4
192.168.0.0/16Private (RFC 1918)Office and home networks; not routed on the internet
198.18.0.0/15BenchmarkingNetwork equipment testing (RFC 2544)
198.51.100.0/24Documentation (TEST-NET-2)For examples; never used on a network
203.0.113.0/24Documentation (TEST-NET-3)For examples; never used on a network
224.0.0.0/4MulticastOne-to-many traffic, such as IPTV and routing protocols
240.0.0.0/4ReservedFuture use; not usable on most systems

IPv6

Special-purpose ranges
RangeNameWhat it is
::/128UnspecifiedNo address; :: means "any address" in settings
::1/128LoopbackThis computer
::ffff:0:0/96IPv4-mappedAn IPv4 address written as IPv6
64:ff9b::/96NAT64IPv4 addresses reached through a NAT64 gateway
100::/64Discard onlyTraffic sent here is dropped (RFC 6666)
2001:db8::/32DocumentationFor examples; never used on a network
2001::/32TeredoIPv6 tunnelled over IPv4 UDP
2002::/166to4IPv6 tunnelled over IPv4 (largely retired)
3fff::/20DocumentationFor examples (RFC 9637)
fc00::/7Unique local (ULA)Private IPv6, like RFC 1918; usually fd00::/8
fe80::/10Link-localEvery IPv6 interface has one; not routed
ff00::/8MulticastOne-to-many traffic; replaces broadcast
2000::/3Global unicastPublic internet addresses

About this tool

A network is written as an address and a prefix length, such as 192.168.1.0/24: the first 24 bits name the network and the rest number the devices on it. The calculator works out where the network starts and ends, how many devices it holds, its subnet and wildcard masks, and the reverse DNS zone to ask your provider for.

It also splits a network into equal smaller ones (one per VLAN or site), turns a range of addresses into the fewest CIDR blocks for a firewall rule, and lists every IPv4 prefix length and the common IPv6 ones in reference tables.

Common questions

Why are two addresses lost in every IPv4 subnet?

The first address names the network and the last is the broadcast address, so a /24 has 256 addresses but 254 for devices. A /31 (a link between two routers) and a /32 (one host) are the exceptions.

What size of IPv6 network should a LAN use?

Always /64. Devices pick their own address within it (SLAAC), which needs the full 64 bits. A site usually gets a /48 or /56 from its provider, which holds 65,536 or 256 LANs.

What is a wildcard mask?

The subnet mask turned inside out: 255.255.255.0 becomes 0.0.0.255. Cisco access lists and OSPF use it to say which bits must match.

Which ranges can I use inside an office?

IPv4: 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. IPv6: unique local addresses from fd00::/8, though most networks use the public prefix from their provider.