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.

Network230.89.80.0/21
Usable hosts2,046
Subnet mask255.255.248.0
Addresses2,048
Network address
230.89.80.0
Broadcast address
230.89.87.255
First usable
230.89.80.1
Last usable
230.89.87.254
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 E6595000 · Integer 3864612864 to 3864614911
Reverse DNS zones
80.89.230.in-addr.arpa
81.89.230.in-addr.arpa
82.89.230.in-addr.arpa
83.89.230.in-addr.arpa
84.89.230.in-addr.arpa
85.89.230.in-addr.arpa
86.89.230.in-addr.arpa
87.89.230.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
Address11100110.01011001.01010000.00000000230.89.80.0
Subnet mask11111111.11111111.11111000.00000000255.255.248.0
Network11100110.01011001.01010000.00000000230.89.80.0
Broadcast11100110.01011001.01010111.11111111230.89.87.255
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)

230.89.80.0/21 makes 2,048 subnets of /32; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1230.89.80.0/32230.89.80.0 to 230.89.80.0—1
2230.89.80.1/32230.89.80.1 to 230.89.80.1—1
3230.89.80.2/32230.89.80.2 to 230.89.80.2—1
4230.89.80.3/32230.89.80.3 to 230.89.80.3—1
5230.89.80.4/32230.89.80.4 to 230.89.80.4—1
6230.89.80.5/32230.89.80.5 to 230.89.80.5—1
7230.89.80.6/32230.89.80.6 to 230.89.80.6—1
8230.89.80.7/32230.89.80.7 to 230.89.80.7—1
9230.89.80.8/32230.89.80.8 to 230.89.80.8—1
10230.89.80.9/32230.89.80.9 to 230.89.80.9—1
11230.89.80.10/32230.89.80.10 to 230.89.80.10—1
12230.89.80.11/32230.89.80.11 to 230.89.80.11—1
13230.89.80.12/32230.89.80.12 to 230.89.80.12—1
14230.89.80.13/32230.89.80.13 to 230.89.80.13—1
15230.89.80.14/32230.89.80.14 to 230.89.80.14—1
16230.89.80.15/32230.89.80.15 to 230.89.80.15—1
17230.89.80.16/32230.89.80.16 to 230.89.80.16—1
18230.89.80.17/32230.89.80.17 to 230.89.80.17—1
19230.89.80.18/32230.89.80.18 to 230.89.80.18—1
20230.89.80.19/32230.89.80.19 to 230.89.80.19—1
21230.89.80.20/32230.89.80.20 to 230.89.80.20—1
22230.89.80.21/32230.89.80.21 to 230.89.80.21—1
23230.89.80.22/32230.89.80.22 to 230.89.80.22—1
24230.89.80.23/32230.89.80.23 to 230.89.80.23—1
25230.89.80.24/32230.89.80.24 to 230.89.80.24—1
26230.89.80.25/32230.89.80.25 to 230.89.80.25—1
27230.89.80.26/32230.89.80.26 to 230.89.80.26—1
28230.89.80.27/32230.89.80.27 to 230.89.80.27—1
29230.89.80.28/32230.89.80.28 to 230.89.80.28—1
30230.89.80.29/32230.89.80.29 to 230.89.80.29—1
31230.89.80.30/32230.89.80.30 to 230.89.80.30—1
32230.89.80.31/32230.89.80.31 to 230.89.80.31—1
33230.89.80.32/32230.89.80.32 to 230.89.80.32—1
34230.89.80.33/32230.89.80.33 to 230.89.80.33—1
35230.89.80.34/32230.89.80.34 to 230.89.80.34—1
36230.89.80.35/32230.89.80.35 to 230.89.80.35—1
37230.89.80.36/32230.89.80.36 to 230.89.80.36—1
38230.89.80.37/32230.89.80.37 to 230.89.80.37—1
39230.89.80.38/32230.89.80.38 to 230.89.80.38—1
40230.89.80.39/32230.89.80.39 to 230.89.80.39—1
41230.89.80.40/32230.89.80.40 to 230.89.80.40—1
42230.89.80.41/32230.89.80.41 to 230.89.80.41—1
43230.89.80.42/32230.89.80.42 to 230.89.80.42—1
44230.89.80.43/32230.89.80.43 to 230.89.80.43—1
45230.89.80.44/32230.89.80.44 to 230.89.80.44—1
46230.89.80.45/32230.89.80.45 to 230.89.80.45—1
47230.89.80.46/32230.89.80.46 to 230.89.80.46—1
48230.89.80.47/32230.89.80.47 to 230.89.80.47—1
49230.89.80.48/32230.89.80.48 to 230.89.80.48—1
50230.89.80.49/32230.89.80.49 to 230.89.80.49—1
51230.89.80.50/32230.89.80.50 to 230.89.80.50—1
52230.89.80.51/32230.89.80.51 to 230.89.80.51—1
53230.89.80.52/32230.89.80.52 to 230.89.80.52—1
54230.89.80.53/32230.89.80.53 to 230.89.80.53—1
55230.89.80.54/32230.89.80.54 to 230.89.80.54—1
56230.89.80.55/32230.89.80.55 to 230.89.80.55—1
57230.89.80.56/32230.89.80.56 to 230.89.80.56—1
58230.89.80.57/32230.89.80.57 to 230.89.80.57—1
59230.89.80.58/32230.89.80.58 to 230.89.80.58—1
60230.89.80.59/32230.89.80.59 to 230.89.80.59—1
61230.89.80.60/32230.89.80.60 to 230.89.80.60—1
62230.89.80.61/32230.89.80.61 to 230.89.80.61—1
63230.89.80.62/32230.89.80.62 to 230.89.80.62—1
64230.89.80.63/32230.89.80.63 to 230.89.80.63—1
65230.89.80.64/32230.89.80.64 to 230.89.80.64—1
66230.89.80.65/32230.89.80.65 to 230.89.80.65—1
67230.89.80.66/32230.89.80.66 to 230.89.80.66—1
68230.89.80.67/32230.89.80.67 to 230.89.80.67—1
69230.89.80.68/32230.89.80.68 to 230.89.80.68—1
70230.89.80.69/32230.89.80.69 to 230.89.80.69—1
71230.89.80.70/32230.89.80.70 to 230.89.80.70—1
72230.89.80.71/32230.89.80.71 to 230.89.80.71—1
73230.89.80.72/32230.89.80.72 to 230.89.80.72—1
74230.89.80.73/32230.89.80.73 to 230.89.80.73—1
75230.89.80.74/32230.89.80.74 to 230.89.80.74—1
76230.89.80.75/32230.89.80.75 to 230.89.80.75—1
77230.89.80.76/32230.89.80.76 to 230.89.80.76—1
78230.89.80.77/32230.89.80.77 to 230.89.80.77—1
79230.89.80.78/32230.89.80.78 to 230.89.80.78—1
80230.89.80.79/32230.89.80.79 to 230.89.80.79—1
81230.89.80.80/32230.89.80.80 to 230.89.80.80—1
82230.89.80.81/32230.89.80.81 to 230.89.80.81—1
83230.89.80.82/32230.89.80.82 to 230.89.80.82—1
84230.89.80.83/32230.89.80.83 to 230.89.80.83—1
85230.89.80.84/32230.89.80.84 to 230.89.80.84—1
86230.89.80.85/32230.89.80.85 to 230.89.80.85—1
87230.89.80.86/32230.89.80.86 to 230.89.80.86—1
88230.89.80.87/32230.89.80.87 to 230.89.80.87—1
89230.89.80.88/32230.89.80.88 to 230.89.80.88—1
90230.89.80.89/32230.89.80.89 to 230.89.80.89—1
91230.89.80.90/32230.89.80.90 to 230.89.80.90—1
92230.89.80.91/32230.89.80.91 to 230.89.80.91—1
93230.89.80.92/32230.89.80.92 to 230.89.80.92—1
94230.89.80.93/32230.89.80.93 to 230.89.80.93—1
95230.89.80.94/32230.89.80.94 to 230.89.80.94—1
96230.89.80.95/32230.89.80.95 to 230.89.80.95—1
97230.89.80.96/32230.89.80.96 to 230.89.80.96—1
98230.89.80.97/32230.89.80.97 to 230.89.80.97—1
99230.89.80.98/32230.89.80.98 to 230.89.80.98—1
100230.89.80.99/32230.89.80.99 to 230.89.80.99—1
101230.89.80.100/32230.89.80.100 to 230.89.80.100—1
102230.89.80.101/32230.89.80.101 to 230.89.80.101—1
103230.89.80.102/32230.89.80.102 to 230.89.80.102—1
104230.89.80.103/32230.89.80.103 to 230.89.80.103—1
105230.89.80.104/32230.89.80.104 to 230.89.80.104—1
106230.89.80.105/32230.89.80.105 to 230.89.80.105—1
107230.89.80.106/32230.89.80.106 to 230.89.80.106—1
108230.89.80.107/32230.89.80.107 to 230.89.80.107—1
109230.89.80.108/32230.89.80.108 to 230.89.80.108—1
110230.89.80.109/32230.89.80.109 to 230.89.80.109—1
111230.89.80.110/32230.89.80.110 to 230.89.80.110—1
112230.89.80.111/32230.89.80.111 to 230.89.80.111—1
113230.89.80.112/32230.89.80.112 to 230.89.80.112—1
114230.89.80.113/32230.89.80.113 to 230.89.80.113—1
115230.89.80.114/32230.89.80.114 to 230.89.80.114—1
116230.89.80.115/32230.89.80.115 to 230.89.80.115—1
117230.89.80.116/32230.89.80.116 to 230.89.80.116—1
118230.89.80.117/32230.89.80.117 to 230.89.80.117—1
119230.89.80.118/32230.89.80.118 to 230.89.80.118—1
120230.89.80.119/32230.89.80.119 to 230.89.80.119—1
121230.89.80.120/32230.89.80.120 to 230.89.80.120—1
122230.89.80.121/32230.89.80.121 to 230.89.80.121—1
123230.89.80.122/32230.89.80.122 to 230.89.80.122—1
124230.89.80.123/32230.89.80.123 to 230.89.80.123—1
125230.89.80.124/32230.89.80.124 to 230.89.80.124—1
126230.89.80.125/32230.89.80.125 to 230.89.80.125—1
127230.89.80.126/32230.89.80.126 to 230.89.80.126—1
128230.89.80.127/32230.89.80.127 to 230.89.80.127—1
129230.89.80.128/32230.89.80.128 to 230.89.80.128—1
130230.89.80.129/32230.89.80.129 to 230.89.80.129—1
131230.89.80.130/32230.89.80.130 to 230.89.80.130—1
132230.89.80.131/32230.89.80.131 to 230.89.80.131—1
133230.89.80.132/32230.89.80.132 to 230.89.80.132—1
134230.89.80.133/32230.89.80.133 to 230.89.80.133—1
135230.89.80.134/32230.89.80.134 to 230.89.80.134—1
136230.89.80.135/32230.89.80.135 to 230.89.80.135—1
137230.89.80.136/32230.89.80.136 to 230.89.80.136—1
138230.89.80.137/32230.89.80.137 to 230.89.80.137—1
139230.89.80.138/32230.89.80.138 to 230.89.80.138—1
140230.89.80.139/32230.89.80.139 to 230.89.80.139—1
141230.89.80.140/32230.89.80.140 to 230.89.80.140—1
142230.89.80.141/32230.89.80.141 to 230.89.80.141—1
143230.89.80.142/32230.89.80.142 to 230.89.80.142—1
144230.89.80.143/32230.89.80.143 to 230.89.80.143—1
145230.89.80.144/32230.89.80.144 to 230.89.80.144—1
146230.89.80.145/32230.89.80.145 to 230.89.80.145—1
147230.89.80.146/32230.89.80.146 to 230.89.80.146—1
148230.89.80.147/32230.89.80.147 to 230.89.80.147—1
149230.89.80.148/32230.89.80.148 to 230.89.80.148—1
150230.89.80.149/32230.89.80.149 to 230.89.80.149—1
151230.89.80.150/32230.89.80.150 to 230.89.80.150—1
152230.89.80.151/32230.89.80.151 to 230.89.80.151—1
153230.89.80.152/32230.89.80.152 to 230.89.80.152—1
154230.89.80.153/32230.89.80.153 to 230.89.80.153—1
155230.89.80.154/32230.89.80.154 to 230.89.80.154—1
156230.89.80.155/32230.89.80.155 to 230.89.80.155—1
157230.89.80.156/32230.89.80.156 to 230.89.80.156—1
158230.89.80.157/32230.89.80.157 to 230.89.80.157—1
159230.89.80.158/32230.89.80.158 to 230.89.80.158—1
160230.89.80.159/32230.89.80.159 to 230.89.80.159—1
161230.89.80.160/32230.89.80.160 to 230.89.80.160—1
162230.89.80.161/32230.89.80.161 to 230.89.80.161—1
163230.89.80.162/32230.89.80.162 to 230.89.80.162—1
164230.89.80.163/32230.89.80.163 to 230.89.80.163—1
165230.89.80.164/32230.89.80.164 to 230.89.80.164—1
166230.89.80.165/32230.89.80.165 to 230.89.80.165—1
167230.89.80.166/32230.89.80.166 to 230.89.80.166—1
168230.89.80.167/32230.89.80.167 to 230.89.80.167—1
169230.89.80.168/32230.89.80.168 to 230.89.80.168—1
170230.89.80.169/32230.89.80.169 to 230.89.80.169—1
171230.89.80.170/32230.89.80.170 to 230.89.80.170—1
172230.89.80.171/32230.89.80.171 to 230.89.80.171—1
173230.89.80.172/32230.89.80.172 to 230.89.80.172—1
174230.89.80.173/32230.89.80.173 to 230.89.80.173—1
175230.89.80.174/32230.89.80.174 to 230.89.80.174—1
176230.89.80.175/32230.89.80.175 to 230.89.80.175—1
177230.89.80.176/32230.89.80.176 to 230.89.80.176—1
178230.89.80.177/32230.89.80.177 to 230.89.80.177—1
179230.89.80.178/32230.89.80.178 to 230.89.80.178—1
180230.89.80.179/32230.89.80.179 to 230.89.80.179—1
181230.89.80.180/32230.89.80.180 to 230.89.80.180—1
182230.89.80.181/32230.89.80.181 to 230.89.80.181—1
183230.89.80.182/32230.89.80.182 to 230.89.80.182—1
184230.89.80.183/32230.89.80.183 to 230.89.80.183—1
185230.89.80.184/32230.89.80.184 to 230.89.80.184—1
186230.89.80.185/32230.89.80.185 to 230.89.80.185—1
187230.89.80.186/32230.89.80.186 to 230.89.80.186—1
188230.89.80.187/32230.89.80.187 to 230.89.80.187—1
189230.89.80.188/32230.89.80.188 to 230.89.80.188—1
190230.89.80.189/32230.89.80.189 to 230.89.80.189—1
191230.89.80.190/32230.89.80.190 to 230.89.80.190—1
192230.89.80.191/32230.89.80.191 to 230.89.80.191—1
193230.89.80.192/32230.89.80.192 to 230.89.80.192—1
194230.89.80.193/32230.89.80.193 to 230.89.80.193—1
195230.89.80.194/32230.89.80.194 to 230.89.80.194—1
196230.89.80.195/32230.89.80.195 to 230.89.80.195—1
197230.89.80.196/32230.89.80.196 to 230.89.80.196—1
198230.89.80.197/32230.89.80.197 to 230.89.80.197—1
199230.89.80.198/32230.89.80.198 to 230.89.80.198—1
200230.89.80.199/32230.89.80.199 to 230.89.80.199—1
201230.89.80.200/32230.89.80.200 to 230.89.80.200—1
202230.89.80.201/32230.89.80.201 to 230.89.80.201—1
203230.89.80.202/32230.89.80.202 to 230.89.80.202—1
204230.89.80.203/32230.89.80.203 to 230.89.80.203—1
205230.89.80.204/32230.89.80.204 to 230.89.80.204—1
206230.89.80.205/32230.89.80.205 to 230.89.80.205—1
207230.89.80.206/32230.89.80.206 to 230.89.80.206—1
208230.89.80.207/32230.89.80.207 to 230.89.80.207—1
209230.89.80.208/32230.89.80.208 to 230.89.80.208—1
210230.89.80.209/32230.89.80.209 to 230.89.80.209—1
211230.89.80.210/32230.89.80.210 to 230.89.80.210—1
212230.89.80.211/32230.89.80.211 to 230.89.80.211—1
213230.89.80.212/32230.89.80.212 to 230.89.80.212—1
214230.89.80.213/32230.89.80.213 to 230.89.80.213—1
215230.89.80.214/32230.89.80.214 to 230.89.80.214—1
216230.89.80.215/32230.89.80.215 to 230.89.80.215—1
217230.89.80.216/32230.89.80.216 to 230.89.80.216—1
218230.89.80.217/32230.89.80.217 to 230.89.80.217—1
219230.89.80.218/32230.89.80.218 to 230.89.80.218—1
220230.89.80.219/32230.89.80.219 to 230.89.80.219—1
221230.89.80.220/32230.89.80.220 to 230.89.80.220—1
222230.89.80.221/32230.89.80.221 to 230.89.80.221—1
223230.89.80.222/32230.89.80.222 to 230.89.80.222—1
224230.89.80.223/32230.89.80.223 to 230.89.80.223—1
225230.89.80.224/32230.89.80.224 to 230.89.80.224—1
226230.89.80.225/32230.89.80.225 to 230.89.80.225—1
227230.89.80.226/32230.89.80.226 to 230.89.80.226—1
228230.89.80.227/32230.89.80.227 to 230.89.80.227—1
229230.89.80.228/32230.89.80.228 to 230.89.80.228—1
230230.89.80.229/32230.89.80.229 to 230.89.80.229—1
231230.89.80.230/32230.89.80.230 to 230.89.80.230—1
232230.89.80.231/32230.89.80.231 to 230.89.80.231—1
233230.89.80.232/32230.89.80.232 to 230.89.80.232—1
234230.89.80.233/32230.89.80.233 to 230.89.80.233—1
235230.89.80.234/32230.89.80.234 to 230.89.80.234—1
236230.89.80.235/32230.89.80.235 to 230.89.80.235—1
237230.89.80.236/32230.89.80.236 to 230.89.80.236—1
238230.89.80.237/32230.89.80.237 to 230.89.80.237—1
239230.89.80.238/32230.89.80.238 to 230.89.80.238—1
240230.89.80.239/32230.89.80.239 to 230.89.80.239—1
241230.89.80.240/32230.89.80.240 to 230.89.80.240—1
242230.89.80.241/32230.89.80.241 to 230.89.80.241—1
243230.89.80.242/32230.89.80.242 to 230.89.80.242—1
244230.89.80.243/32230.89.80.243 to 230.89.80.243—1
245230.89.80.244/32230.89.80.244 to 230.89.80.244—1
246230.89.80.245/32230.89.80.245 to 230.89.80.245—1
247230.89.80.246/32230.89.80.246 to 230.89.80.246—1
248230.89.80.247/32230.89.80.247 to 230.89.80.247—1
249230.89.80.248/32230.89.80.248 to 230.89.80.248—1
250230.89.80.249/32230.89.80.249 to 230.89.80.249—1
251230.89.80.250/32230.89.80.250 to 230.89.80.250—1
252230.89.80.251/32230.89.80.251 to 230.89.80.251—1
253230.89.80.252/32230.89.80.252 to 230.89.80.252—1
254230.89.80.253/32230.89.80.253 to 230.89.80.253—1
255230.89.80.254/32230.89.80.254 to 230.89.80.254—1
256230.89.80.255/32230.89.80.255 to 230.89.80.255—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.