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.

Network244.65.58.0/23
Usable hosts510
Subnet mask255.255.254.0
Addresses512
Network address
244.65.58.0
Broadcast address
244.65.59.255
First usable
244.65.58.1
Last usable
244.65.59.254
Usable hosts
510 (512 less the network and broadcast addresses)
Subnet mask
255.255.254.0
Wildcard mask
0.0.1.255 (Cisco ACLs, OSPF)
Prefix length
/23
Type
Reserved 240.0.0.0/4
Future use; not usable on most systems
Old class
E (reserved)
As numbers
Hex F4413A00 · Integer 4097915392 to 4097915903
Reverse DNS zones
58.65.244.in-addr.arpa
59.65.244.in-addr.arpa
/23 is not on a 8-bit boundary, so it takes 2 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11110100.01000001.00111010.00000000244.65.58.0
Subnet mask11111111.11111111.11111110.00000000255.255.254.0
Network11110100.01000001.00111010.00000000244.65.58.0
Broadcast11110100.01000001.00111011.11111111244.65.59.255
Split into smaller subnets/32
/24 (2)/25 (4)/26 (8)/27 (16)/28 (32)/29 (64)/30 (128)/31 (256)/32 (512)

244.65.58.0/23 makes 512 subnets of /32; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1244.65.58.0/32244.65.58.0 to 244.65.58.0—1
2244.65.58.1/32244.65.58.1 to 244.65.58.1—1
3244.65.58.2/32244.65.58.2 to 244.65.58.2—1
4244.65.58.3/32244.65.58.3 to 244.65.58.3—1
5244.65.58.4/32244.65.58.4 to 244.65.58.4—1
6244.65.58.5/32244.65.58.5 to 244.65.58.5—1
7244.65.58.6/32244.65.58.6 to 244.65.58.6—1
8244.65.58.7/32244.65.58.7 to 244.65.58.7—1
9244.65.58.8/32244.65.58.8 to 244.65.58.8—1
10244.65.58.9/32244.65.58.9 to 244.65.58.9—1
11244.65.58.10/32244.65.58.10 to 244.65.58.10—1
12244.65.58.11/32244.65.58.11 to 244.65.58.11—1
13244.65.58.12/32244.65.58.12 to 244.65.58.12—1
14244.65.58.13/32244.65.58.13 to 244.65.58.13—1
15244.65.58.14/32244.65.58.14 to 244.65.58.14—1
16244.65.58.15/32244.65.58.15 to 244.65.58.15—1
17244.65.58.16/32244.65.58.16 to 244.65.58.16—1
18244.65.58.17/32244.65.58.17 to 244.65.58.17—1
19244.65.58.18/32244.65.58.18 to 244.65.58.18—1
20244.65.58.19/32244.65.58.19 to 244.65.58.19—1
21244.65.58.20/32244.65.58.20 to 244.65.58.20—1
22244.65.58.21/32244.65.58.21 to 244.65.58.21—1
23244.65.58.22/32244.65.58.22 to 244.65.58.22—1
24244.65.58.23/32244.65.58.23 to 244.65.58.23—1
25244.65.58.24/32244.65.58.24 to 244.65.58.24—1
26244.65.58.25/32244.65.58.25 to 244.65.58.25—1
27244.65.58.26/32244.65.58.26 to 244.65.58.26—1
28244.65.58.27/32244.65.58.27 to 244.65.58.27—1
29244.65.58.28/32244.65.58.28 to 244.65.58.28—1
30244.65.58.29/32244.65.58.29 to 244.65.58.29—1
31244.65.58.30/32244.65.58.30 to 244.65.58.30—1
32244.65.58.31/32244.65.58.31 to 244.65.58.31—1
33244.65.58.32/32244.65.58.32 to 244.65.58.32—1
34244.65.58.33/32244.65.58.33 to 244.65.58.33—1
35244.65.58.34/32244.65.58.34 to 244.65.58.34—1
36244.65.58.35/32244.65.58.35 to 244.65.58.35—1
37244.65.58.36/32244.65.58.36 to 244.65.58.36—1
38244.65.58.37/32244.65.58.37 to 244.65.58.37—1
39244.65.58.38/32244.65.58.38 to 244.65.58.38—1
40244.65.58.39/32244.65.58.39 to 244.65.58.39—1
41244.65.58.40/32244.65.58.40 to 244.65.58.40—1
42244.65.58.41/32244.65.58.41 to 244.65.58.41—1
43244.65.58.42/32244.65.58.42 to 244.65.58.42—1
44244.65.58.43/32244.65.58.43 to 244.65.58.43—1
45244.65.58.44/32244.65.58.44 to 244.65.58.44—1
46244.65.58.45/32244.65.58.45 to 244.65.58.45—1
47244.65.58.46/32244.65.58.46 to 244.65.58.46—1
48244.65.58.47/32244.65.58.47 to 244.65.58.47—1
49244.65.58.48/32244.65.58.48 to 244.65.58.48—1
50244.65.58.49/32244.65.58.49 to 244.65.58.49—1
51244.65.58.50/32244.65.58.50 to 244.65.58.50—1
52244.65.58.51/32244.65.58.51 to 244.65.58.51—1
53244.65.58.52/32244.65.58.52 to 244.65.58.52—1
54244.65.58.53/32244.65.58.53 to 244.65.58.53—1
55244.65.58.54/32244.65.58.54 to 244.65.58.54—1
56244.65.58.55/32244.65.58.55 to 244.65.58.55—1
57244.65.58.56/32244.65.58.56 to 244.65.58.56—1
58244.65.58.57/32244.65.58.57 to 244.65.58.57—1
59244.65.58.58/32244.65.58.58 to 244.65.58.58—1
60244.65.58.59/32244.65.58.59 to 244.65.58.59—1
61244.65.58.60/32244.65.58.60 to 244.65.58.60—1
62244.65.58.61/32244.65.58.61 to 244.65.58.61—1
63244.65.58.62/32244.65.58.62 to 244.65.58.62—1
64244.65.58.63/32244.65.58.63 to 244.65.58.63—1
65244.65.58.64/32244.65.58.64 to 244.65.58.64—1
66244.65.58.65/32244.65.58.65 to 244.65.58.65—1
67244.65.58.66/32244.65.58.66 to 244.65.58.66—1
68244.65.58.67/32244.65.58.67 to 244.65.58.67—1
69244.65.58.68/32244.65.58.68 to 244.65.58.68—1
70244.65.58.69/32244.65.58.69 to 244.65.58.69—1
71244.65.58.70/32244.65.58.70 to 244.65.58.70—1
72244.65.58.71/32244.65.58.71 to 244.65.58.71—1
73244.65.58.72/32244.65.58.72 to 244.65.58.72—1
74244.65.58.73/32244.65.58.73 to 244.65.58.73—1
75244.65.58.74/32244.65.58.74 to 244.65.58.74—1
76244.65.58.75/32244.65.58.75 to 244.65.58.75—1
77244.65.58.76/32244.65.58.76 to 244.65.58.76—1
78244.65.58.77/32244.65.58.77 to 244.65.58.77—1
79244.65.58.78/32244.65.58.78 to 244.65.58.78—1
80244.65.58.79/32244.65.58.79 to 244.65.58.79—1
81244.65.58.80/32244.65.58.80 to 244.65.58.80—1
82244.65.58.81/32244.65.58.81 to 244.65.58.81—1
83244.65.58.82/32244.65.58.82 to 244.65.58.82—1
84244.65.58.83/32244.65.58.83 to 244.65.58.83—1
85244.65.58.84/32244.65.58.84 to 244.65.58.84—1
86244.65.58.85/32244.65.58.85 to 244.65.58.85—1
87244.65.58.86/32244.65.58.86 to 244.65.58.86—1
88244.65.58.87/32244.65.58.87 to 244.65.58.87—1
89244.65.58.88/32244.65.58.88 to 244.65.58.88—1
90244.65.58.89/32244.65.58.89 to 244.65.58.89—1
91244.65.58.90/32244.65.58.90 to 244.65.58.90—1
92244.65.58.91/32244.65.58.91 to 244.65.58.91—1
93244.65.58.92/32244.65.58.92 to 244.65.58.92—1
94244.65.58.93/32244.65.58.93 to 244.65.58.93—1
95244.65.58.94/32244.65.58.94 to 244.65.58.94—1
96244.65.58.95/32244.65.58.95 to 244.65.58.95—1
97244.65.58.96/32244.65.58.96 to 244.65.58.96—1
98244.65.58.97/32244.65.58.97 to 244.65.58.97—1
99244.65.58.98/32244.65.58.98 to 244.65.58.98—1
100244.65.58.99/32244.65.58.99 to 244.65.58.99—1
101244.65.58.100/32244.65.58.100 to 244.65.58.100—1
102244.65.58.101/32244.65.58.101 to 244.65.58.101—1
103244.65.58.102/32244.65.58.102 to 244.65.58.102—1
104244.65.58.103/32244.65.58.103 to 244.65.58.103—1
105244.65.58.104/32244.65.58.104 to 244.65.58.104—1
106244.65.58.105/32244.65.58.105 to 244.65.58.105—1
107244.65.58.106/32244.65.58.106 to 244.65.58.106—1
108244.65.58.107/32244.65.58.107 to 244.65.58.107—1
109244.65.58.108/32244.65.58.108 to 244.65.58.108—1
110244.65.58.109/32244.65.58.109 to 244.65.58.109—1
111244.65.58.110/32244.65.58.110 to 244.65.58.110—1
112244.65.58.111/32244.65.58.111 to 244.65.58.111—1
113244.65.58.112/32244.65.58.112 to 244.65.58.112—1
114244.65.58.113/32244.65.58.113 to 244.65.58.113—1
115244.65.58.114/32244.65.58.114 to 244.65.58.114—1
116244.65.58.115/32244.65.58.115 to 244.65.58.115—1
117244.65.58.116/32244.65.58.116 to 244.65.58.116—1
118244.65.58.117/32244.65.58.117 to 244.65.58.117—1
119244.65.58.118/32244.65.58.118 to 244.65.58.118—1
120244.65.58.119/32244.65.58.119 to 244.65.58.119—1
121244.65.58.120/32244.65.58.120 to 244.65.58.120—1
122244.65.58.121/32244.65.58.121 to 244.65.58.121—1
123244.65.58.122/32244.65.58.122 to 244.65.58.122—1
124244.65.58.123/32244.65.58.123 to 244.65.58.123—1
125244.65.58.124/32244.65.58.124 to 244.65.58.124—1
126244.65.58.125/32244.65.58.125 to 244.65.58.125—1
127244.65.58.126/32244.65.58.126 to 244.65.58.126—1
128244.65.58.127/32244.65.58.127 to 244.65.58.127—1
129244.65.58.128/32244.65.58.128 to 244.65.58.128—1
130244.65.58.129/32244.65.58.129 to 244.65.58.129—1
131244.65.58.130/32244.65.58.130 to 244.65.58.130—1
132244.65.58.131/32244.65.58.131 to 244.65.58.131—1
133244.65.58.132/32244.65.58.132 to 244.65.58.132—1
134244.65.58.133/32244.65.58.133 to 244.65.58.133—1
135244.65.58.134/32244.65.58.134 to 244.65.58.134—1
136244.65.58.135/32244.65.58.135 to 244.65.58.135—1
137244.65.58.136/32244.65.58.136 to 244.65.58.136—1
138244.65.58.137/32244.65.58.137 to 244.65.58.137—1
139244.65.58.138/32244.65.58.138 to 244.65.58.138—1
140244.65.58.139/32244.65.58.139 to 244.65.58.139—1
141244.65.58.140/32244.65.58.140 to 244.65.58.140—1
142244.65.58.141/32244.65.58.141 to 244.65.58.141—1
143244.65.58.142/32244.65.58.142 to 244.65.58.142—1
144244.65.58.143/32244.65.58.143 to 244.65.58.143—1
145244.65.58.144/32244.65.58.144 to 244.65.58.144—1
146244.65.58.145/32244.65.58.145 to 244.65.58.145—1
147244.65.58.146/32244.65.58.146 to 244.65.58.146—1
148244.65.58.147/32244.65.58.147 to 244.65.58.147—1
149244.65.58.148/32244.65.58.148 to 244.65.58.148—1
150244.65.58.149/32244.65.58.149 to 244.65.58.149—1
151244.65.58.150/32244.65.58.150 to 244.65.58.150—1
152244.65.58.151/32244.65.58.151 to 244.65.58.151—1
153244.65.58.152/32244.65.58.152 to 244.65.58.152—1
154244.65.58.153/32244.65.58.153 to 244.65.58.153—1
155244.65.58.154/32244.65.58.154 to 244.65.58.154—1
156244.65.58.155/32244.65.58.155 to 244.65.58.155—1
157244.65.58.156/32244.65.58.156 to 244.65.58.156—1
158244.65.58.157/32244.65.58.157 to 244.65.58.157—1
159244.65.58.158/32244.65.58.158 to 244.65.58.158—1
160244.65.58.159/32244.65.58.159 to 244.65.58.159—1
161244.65.58.160/32244.65.58.160 to 244.65.58.160—1
162244.65.58.161/32244.65.58.161 to 244.65.58.161—1
163244.65.58.162/32244.65.58.162 to 244.65.58.162—1
164244.65.58.163/32244.65.58.163 to 244.65.58.163—1
165244.65.58.164/32244.65.58.164 to 244.65.58.164—1
166244.65.58.165/32244.65.58.165 to 244.65.58.165—1
167244.65.58.166/32244.65.58.166 to 244.65.58.166—1
168244.65.58.167/32244.65.58.167 to 244.65.58.167—1
169244.65.58.168/32244.65.58.168 to 244.65.58.168—1
170244.65.58.169/32244.65.58.169 to 244.65.58.169—1
171244.65.58.170/32244.65.58.170 to 244.65.58.170—1
172244.65.58.171/32244.65.58.171 to 244.65.58.171—1
173244.65.58.172/32244.65.58.172 to 244.65.58.172—1
174244.65.58.173/32244.65.58.173 to 244.65.58.173—1
175244.65.58.174/32244.65.58.174 to 244.65.58.174—1
176244.65.58.175/32244.65.58.175 to 244.65.58.175—1
177244.65.58.176/32244.65.58.176 to 244.65.58.176—1
178244.65.58.177/32244.65.58.177 to 244.65.58.177—1
179244.65.58.178/32244.65.58.178 to 244.65.58.178—1
180244.65.58.179/32244.65.58.179 to 244.65.58.179—1
181244.65.58.180/32244.65.58.180 to 244.65.58.180—1
182244.65.58.181/32244.65.58.181 to 244.65.58.181—1
183244.65.58.182/32244.65.58.182 to 244.65.58.182—1
184244.65.58.183/32244.65.58.183 to 244.65.58.183—1
185244.65.58.184/32244.65.58.184 to 244.65.58.184—1
186244.65.58.185/32244.65.58.185 to 244.65.58.185—1
187244.65.58.186/32244.65.58.186 to 244.65.58.186—1
188244.65.58.187/32244.65.58.187 to 244.65.58.187—1
189244.65.58.188/32244.65.58.188 to 244.65.58.188—1
190244.65.58.189/32244.65.58.189 to 244.65.58.189—1
191244.65.58.190/32244.65.58.190 to 244.65.58.190—1
192244.65.58.191/32244.65.58.191 to 244.65.58.191—1
193244.65.58.192/32244.65.58.192 to 244.65.58.192—1
194244.65.58.193/32244.65.58.193 to 244.65.58.193—1
195244.65.58.194/32244.65.58.194 to 244.65.58.194—1
196244.65.58.195/32244.65.58.195 to 244.65.58.195—1
197244.65.58.196/32244.65.58.196 to 244.65.58.196—1
198244.65.58.197/32244.65.58.197 to 244.65.58.197—1
199244.65.58.198/32244.65.58.198 to 244.65.58.198—1
200244.65.58.199/32244.65.58.199 to 244.65.58.199—1
201244.65.58.200/32244.65.58.200 to 244.65.58.200—1
202244.65.58.201/32244.65.58.201 to 244.65.58.201—1
203244.65.58.202/32244.65.58.202 to 244.65.58.202—1
204244.65.58.203/32244.65.58.203 to 244.65.58.203—1
205244.65.58.204/32244.65.58.204 to 244.65.58.204—1
206244.65.58.205/32244.65.58.205 to 244.65.58.205—1
207244.65.58.206/32244.65.58.206 to 244.65.58.206—1
208244.65.58.207/32244.65.58.207 to 244.65.58.207—1
209244.65.58.208/32244.65.58.208 to 244.65.58.208—1
210244.65.58.209/32244.65.58.209 to 244.65.58.209—1
211244.65.58.210/32244.65.58.210 to 244.65.58.210—1
212244.65.58.211/32244.65.58.211 to 244.65.58.211—1
213244.65.58.212/32244.65.58.212 to 244.65.58.212—1
214244.65.58.213/32244.65.58.213 to 244.65.58.213—1
215244.65.58.214/32244.65.58.214 to 244.65.58.214—1
216244.65.58.215/32244.65.58.215 to 244.65.58.215—1
217244.65.58.216/32244.65.58.216 to 244.65.58.216—1
218244.65.58.217/32244.65.58.217 to 244.65.58.217—1
219244.65.58.218/32244.65.58.218 to 244.65.58.218—1
220244.65.58.219/32244.65.58.219 to 244.65.58.219—1
221244.65.58.220/32244.65.58.220 to 244.65.58.220—1
222244.65.58.221/32244.65.58.221 to 244.65.58.221—1
223244.65.58.222/32244.65.58.222 to 244.65.58.222—1
224244.65.58.223/32244.65.58.223 to 244.65.58.223—1
225244.65.58.224/32244.65.58.224 to 244.65.58.224—1
226244.65.58.225/32244.65.58.225 to 244.65.58.225—1
227244.65.58.226/32244.65.58.226 to 244.65.58.226—1
228244.65.58.227/32244.65.58.227 to 244.65.58.227—1
229244.65.58.228/32244.65.58.228 to 244.65.58.228—1
230244.65.58.229/32244.65.58.229 to 244.65.58.229—1
231244.65.58.230/32244.65.58.230 to 244.65.58.230—1
232244.65.58.231/32244.65.58.231 to 244.65.58.231—1
233244.65.58.232/32244.65.58.232 to 244.65.58.232—1
234244.65.58.233/32244.65.58.233 to 244.65.58.233—1
235244.65.58.234/32244.65.58.234 to 244.65.58.234—1
236244.65.58.235/32244.65.58.235 to 244.65.58.235—1
237244.65.58.236/32244.65.58.236 to 244.65.58.236—1
238244.65.58.237/32244.65.58.237 to 244.65.58.237—1
239244.65.58.238/32244.65.58.238 to 244.65.58.238—1
240244.65.58.239/32244.65.58.239 to 244.65.58.239—1
241244.65.58.240/32244.65.58.240 to 244.65.58.240—1
242244.65.58.241/32244.65.58.241 to 244.65.58.241—1
243244.65.58.242/32244.65.58.242 to 244.65.58.242—1
244244.65.58.243/32244.65.58.243 to 244.65.58.243—1
245244.65.58.244/32244.65.58.244 to 244.65.58.244—1
246244.65.58.245/32244.65.58.245 to 244.65.58.245—1
247244.65.58.246/32244.65.58.246 to 244.65.58.246—1
248244.65.58.247/32244.65.58.247 to 244.65.58.247—1
249244.65.58.248/32244.65.58.248 to 244.65.58.248—1
250244.65.58.249/32244.65.58.249 to 244.65.58.249—1
251244.65.58.250/32244.65.58.250 to 244.65.58.250—1
252244.65.58.251/32244.65.58.251 to 244.65.58.251—1
253244.65.58.252/32244.65.58.252 to 244.65.58.252—1
254244.65.58.253/32244.65.58.253 to 244.65.58.253—1
255244.65.58.254/32244.65.58.254 to 244.65.58.254—1
256244.65.58.255/32244.65.58.255 to 244.65.58.255—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.