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.

Network245.232.56.0/23
Usable hosts510
Subnet mask255.255.254.0
Addresses512
Network address
245.232.56.0
Broadcast address
245.232.57.255
First usable
245.232.56.1
Last usable
245.232.57.254
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 F5E83800 · Integer 4125636608 to 4125637119
Reverse DNS zones
56.232.245.in-addr.arpa
57.232.245.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
Address11110101.11101000.00111000.00000000245.232.56.0
Subnet mask11111111.11111111.11111110.00000000255.255.254.0
Network11110101.11101000.00111000.00000000245.232.56.0
Broadcast11110101.11101000.00111001.11111111245.232.57.255
Split into smaller subnets/32
/24 (2)/25 (4)/26 (8)/27 (16)/28 (32)/29 (64)/30 (128)/31 (256)/32 (512)

245.232.56.0/23 makes 512 subnets of /32; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1245.232.56.0/32245.232.56.0 to 245.232.56.0—1
2245.232.56.1/32245.232.56.1 to 245.232.56.1—1
3245.232.56.2/32245.232.56.2 to 245.232.56.2—1
4245.232.56.3/32245.232.56.3 to 245.232.56.3—1
5245.232.56.4/32245.232.56.4 to 245.232.56.4—1
6245.232.56.5/32245.232.56.5 to 245.232.56.5—1
7245.232.56.6/32245.232.56.6 to 245.232.56.6—1
8245.232.56.7/32245.232.56.7 to 245.232.56.7—1
9245.232.56.8/32245.232.56.8 to 245.232.56.8—1
10245.232.56.9/32245.232.56.9 to 245.232.56.9—1
11245.232.56.10/32245.232.56.10 to 245.232.56.10—1
12245.232.56.11/32245.232.56.11 to 245.232.56.11—1
13245.232.56.12/32245.232.56.12 to 245.232.56.12—1
14245.232.56.13/32245.232.56.13 to 245.232.56.13—1
15245.232.56.14/32245.232.56.14 to 245.232.56.14—1
16245.232.56.15/32245.232.56.15 to 245.232.56.15—1
17245.232.56.16/32245.232.56.16 to 245.232.56.16—1
18245.232.56.17/32245.232.56.17 to 245.232.56.17—1
19245.232.56.18/32245.232.56.18 to 245.232.56.18—1
20245.232.56.19/32245.232.56.19 to 245.232.56.19—1
21245.232.56.20/32245.232.56.20 to 245.232.56.20—1
22245.232.56.21/32245.232.56.21 to 245.232.56.21—1
23245.232.56.22/32245.232.56.22 to 245.232.56.22—1
24245.232.56.23/32245.232.56.23 to 245.232.56.23—1
25245.232.56.24/32245.232.56.24 to 245.232.56.24—1
26245.232.56.25/32245.232.56.25 to 245.232.56.25—1
27245.232.56.26/32245.232.56.26 to 245.232.56.26—1
28245.232.56.27/32245.232.56.27 to 245.232.56.27—1
29245.232.56.28/32245.232.56.28 to 245.232.56.28—1
30245.232.56.29/32245.232.56.29 to 245.232.56.29—1
31245.232.56.30/32245.232.56.30 to 245.232.56.30—1
32245.232.56.31/32245.232.56.31 to 245.232.56.31—1
33245.232.56.32/32245.232.56.32 to 245.232.56.32—1
34245.232.56.33/32245.232.56.33 to 245.232.56.33—1
35245.232.56.34/32245.232.56.34 to 245.232.56.34—1
36245.232.56.35/32245.232.56.35 to 245.232.56.35—1
37245.232.56.36/32245.232.56.36 to 245.232.56.36—1
38245.232.56.37/32245.232.56.37 to 245.232.56.37—1
39245.232.56.38/32245.232.56.38 to 245.232.56.38—1
40245.232.56.39/32245.232.56.39 to 245.232.56.39—1
41245.232.56.40/32245.232.56.40 to 245.232.56.40—1
42245.232.56.41/32245.232.56.41 to 245.232.56.41—1
43245.232.56.42/32245.232.56.42 to 245.232.56.42—1
44245.232.56.43/32245.232.56.43 to 245.232.56.43—1
45245.232.56.44/32245.232.56.44 to 245.232.56.44—1
46245.232.56.45/32245.232.56.45 to 245.232.56.45—1
47245.232.56.46/32245.232.56.46 to 245.232.56.46—1
48245.232.56.47/32245.232.56.47 to 245.232.56.47—1
49245.232.56.48/32245.232.56.48 to 245.232.56.48—1
50245.232.56.49/32245.232.56.49 to 245.232.56.49—1
51245.232.56.50/32245.232.56.50 to 245.232.56.50—1
52245.232.56.51/32245.232.56.51 to 245.232.56.51—1
53245.232.56.52/32245.232.56.52 to 245.232.56.52—1
54245.232.56.53/32245.232.56.53 to 245.232.56.53—1
55245.232.56.54/32245.232.56.54 to 245.232.56.54—1
56245.232.56.55/32245.232.56.55 to 245.232.56.55—1
57245.232.56.56/32245.232.56.56 to 245.232.56.56—1
58245.232.56.57/32245.232.56.57 to 245.232.56.57—1
59245.232.56.58/32245.232.56.58 to 245.232.56.58—1
60245.232.56.59/32245.232.56.59 to 245.232.56.59—1
61245.232.56.60/32245.232.56.60 to 245.232.56.60—1
62245.232.56.61/32245.232.56.61 to 245.232.56.61—1
63245.232.56.62/32245.232.56.62 to 245.232.56.62—1
64245.232.56.63/32245.232.56.63 to 245.232.56.63—1
65245.232.56.64/32245.232.56.64 to 245.232.56.64—1
66245.232.56.65/32245.232.56.65 to 245.232.56.65—1
67245.232.56.66/32245.232.56.66 to 245.232.56.66—1
68245.232.56.67/32245.232.56.67 to 245.232.56.67—1
69245.232.56.68/32245.232.56.68 to 245.232.56.68—1
70245.232.56.69/32245.232.56.69 to 245.232.56.69—1
71245.232.56.70/32245.232.56.70 to 245.232.56.70—1
72245.232.56.71/32245.232.56.71 to 245.232.56.71—1
73245.232.56.72/32245.232.56.72 to 245.232.56.72—1
74245.232.56.73/32245.232.56.73 to 245.232.56.73—1
75245.232.56.74/32245.232.56.74 to 245.232.56.74—1
76245.232.56.75/32245.232.56.75 to 245.232.56.75—1
77245.232.56.76/32245.232.56.76 to 245.232.56.76—1
78245.232.56.77/32245.232.56.77 to 245.232.56.77—1
79245.232.56.78/32245.232.56.78 to 245.232.56.78—1
80245.232.56.79/32245.232.56.79 to 245.232.56.79—1
81245.232.56.80/32245.232.56.80 to 245.232.56.80—1
82245.232.56.81/32245.232.56.81 to 245.232.56.81—1
83245.232.56.82/32245.232.56.82 to 245.232.56.82—1
84245.232.56.83/32245.232.56.83 to 245.232.56.83—1
85245.232.56.84/32245.232.56.84 to 245.232.56.84—1
86245.232.56.85/32245.232.56.85 to 245.232.56.85—1
87245.232.56.86/32245.232.56.86 to 245.232.56.86—1
88245.232.56.87/32245.232.56.87 to 245.232.56.87—1
89245.232.56.88/32245.232.56.88 to 245.232.56.88—1
90245.232.56.89/32245.232.56.89 to 245.232.56.89—1
91245.232.56.90/32245.232.56.90 to 245.232.56.90—1
92245.232.56.91/32245.232.56.91 to 245.232.56.91—1
93245.232.56.92/32245.232.56.92 to 245.232.56.92—1
94245.232.56.93/32245.232.56.93 to 245.232.56.93—1
95245.232.56.94/32245.232.56.94 to 245.232.56.94—1
96245.232.56.95/32245.232.56.95 to 245.232.56.95—1
97245.232.56.96/32245.232.56.96 to 245.232.56.96—1
98245.232.56.97/32245.232.56.97 to 245.232.56.97—1
99245.232.56.98/32245.232.56.98 to 245.232.56.98—1
100245.232.56.99/32245.232.56.99 to 245.232.56.99—1
101245.232.56.100/32245.232.56.100 to 245.232.56.100—1
102245.232.56.101/32245.232.56.101 to 245.232.56.101—1
103245.232.56.102/32245.232.56.102 to 245.232.56.102—1
104245.232.56.103/32245.232.56.103 to 245.232.56.103—1
105245.232.56.104/32245.232.56.104 to 245.232.56.104—1
106245.232.56.105/32245.232.56.105 to 245.232.56.105—1
107245.232.56.106/32245.232.56.106 to 245.232.56.106—1
108245.232.56.107/32245.232.56.107 to 245.232.56.107—1
109245.232.56.108/32245.232.56.108 to 245.232.56.108—1
110245.232.56.109/32245.232.56.109 to 245.232.56.109—1
111245.232.56.110/32245.232.56.110 to 245.232.56.110—1
112245.232.56.111/32245.232.56.111 to 245.232.56.111—1
113245.232.56.112/32245.232.56.112 to 245.232.56.112—1
114245.232.56.113/32245.232.56.113 to 245.232.56.113—1
115245.232.56.114/32245.232.56.114 to 245.232.56.114—1
116245.232.56.115/32245.232.56.115 to 245.232.56.115—1
117245.232.56.116/32245.232.56.116 to 245.232.56.116—1
118245.232.56.117/32245.232.56.117 to 245.232.56.117—1
119245.232.56.118/32245.232.56.118 to 245.232.56.118—1
120245.232.56.119/32245.232.56.119 to 245.232.56.119—1
121245.232.56.120/32245.232.56.120 to 245.232.56.120—1
122245.232.56.121/32245.232.56.121 to 245.232.56.121—1
123245.232.56.122/32245.232.56.122 to 245.232.56.122—1
124245.232.56.123/32245.232.56.123 to 245.232.56.123—1
125245.232.56.124/32245.232.56.124 to 245.232.56.124—1
126245.232.56.125/32245.232.56.125 to 245.232.56.125—1
127245.232.56.126/32245.232.56.126 to 245.232.56.126—1
128245.232.56.127/32245.232.56.127 to 245.232.56.127—1
129245.232.56.128/32245.232.56.128 to 245.232.56.128—1
130245.232.56.129/32245.232.56.129 to 245.232.56.129—1
131245.232.56.130/32245.232.56.130 to 245.232.56.130—1
132245.232.56.131/32245.232.56.131 to 245.232.56.131—1
133245.232.56.132/32245.232.56.132 to 245.232.56.132—1
134245.232.56.133/32245.232.56.133 to 245.232.56.133—1
135245.232.56.134/32245.232.56.134 to 245.232.56.134—1
136245.232.56.135/32245.232.56.135 to 245.232.56.135—1
137245.232.56.136/32245.232.56.136 to 245.232.56.136—1
138245.232.56.137/32245.232.56.137 to 245.232.56.137—1
139245.232.56.138/32245.232.56.138 to 245.232.56.138—1
140245.232.56.139/32245.232.56.139 to 245.232.56.139—1
141245.232.56.140/32245.232.56.140 to 245.232.56.140—1
142245.232.56.141/32245.232.56.141 to 245.232.56.141—1
143245.232.56.142/32245.232.56.142 to 245.232.56.142—1
144245.232.56.143/32245.232.56.143 to 245.232.56.143—1
145245.232.56.144/32245.232.56.144 to 245.232.56.144—1
146245.232.56.145/32245.232.56.145 to 245.232.56.145—1
147245.232.56.146/32245.232.56.146 to 245.232.56.146—1
148245.232.56.147/32245.232.56.147 to 245.232.56.147—1
149245.232.56.148/32245.232.56.148 to 245.232.56.148—1
150245.232.56.149/32245.232.56.149 to 245.232.56.149—1
151245.232.56.150/32245.232.56.150 to 245.232.56.150—1
152245.232.56.151/32245.232.56.151 to 245.232.56.151—1
153245.232.56.152/32245.232.56.152 to 245.232.56.152—1
154245.232.56.153/32245.232.56.153 to 245.232.56.153—1
155245.232.56.154/32245.232.56.154 to 245.232.56.154—1
156245.232.56.155/32245.232.56.155 to 245.232.56.155—1
157245.232.56.156/32245.232.56.156 to 245.232.56.156—1
158245.232.56.157/32245.232.56.157 to 245.232.56.157—1
159245.232.56.158/32245.232.56.158 to 245.232.56.158—1
160245.232.56.159/32245.232.56.159 to 245.232.56.159—1
161245.232.56.160/32245.232.56.160 to 245.232.56.160—1
162245.232.56.161/32245.232.56.161 to 245.232.56.161—1
163245.232.56.162/32245.232.56.162 to 245.232.56.162—1
164245.232.56.163/32245.232.56.163 to 245.232.56.163—1
165245.232.56.164/32245.232.56.164 to 245.232.56.164—1
166245.232.56.165/32245.232.56.165 to 245.232.56.165—1
167245.232.56.166/32245.232.56.166 to 245.232.56.166—1
168245.232.56.167/32245.232.56.167 to 245.232.56.167—1
169245.232.56.168/32245.232.56.168 to 245.232.56.168—1
170245.232.56.169/32245.232.56.169 to 245.232.56.169—1
171245.232.56.170/32245.232.56.170 to 245.232.56.170—1
172245.232.56.171/32245.232.56.171 to 245.232.56.171—1
173245.232.56.172/32245.232.56.172 to 245.232.56.172—1
174245.232.56.173/32245.232.56.173 to 245.232.56.173—1
175245.232.56.174/32245.232.56.174 to 245.232.56.174—1
176245.232.56.175/32245.232.56.175 to 245.232.56.175—1
177245.232.56.176/32245.232.56.176 to 245.232.56.176—1
178245.232.56.177/32245.232.56.177 to 245.232.56.177—1
179245.232.56.178/32245.232.56.178 to 245.232.56.178—1
180245.232.56.179/32245.232.56.179 to 245.232.56.179—1
181245.232.56.180/32245.232.56.180 to 245.232.56.180—1
182245.232.56.181/32245.232.56.181 to 245.232.56.181—1
183245.232.56.182/32245.232.56.182 to 245.232.56.182—1
184245.232.56.183/32245.232.56.183 to 245.232.56.183—1
185245.232.56.184/32245.232.56.184 to 245.232.56.184—1
186245.232.56.185/32245.232.56.185 to 245.232.56.185—1
187245.232.56.186/32245.232.56.186 to 245.232.56.186—1
188245.232.56.187/32245.232.56.187 to 245.232.56.187—1
189245.232.56.188/32245.232.56.188 to 245.232.56.188—1
190245.232.56.189/32245.232.56.189 to 245.232.56.189—1
191245.232.56.190/32245.232.56.190 to 245.232.56.190—1
192245.232.56.191/32245.232.56.191 to 245.232.56.191—1
193245.232.56.192/32245.232.56.192 to 245.232.56.192—1
194245.232.56.193/32245.232.56.193 to 245.232.56.193—1
195245.232.56.194/32245.232.56.194 to 245.232.56.194—1
196245.232.56.195/32245.232.56.195 to 245.232.56.195—1
197245.232.56.196/32245.232.56.196 to 245.232.56.196—1
198245.232.56.197/32245.232.56.197 to 245.232.56.197—1
199245.232.56.198/32245.232.56.198 to 245.232.56.198—1
200245.232.56.199/32245.232.56.199 to 245.232.56.199—1
201245.232.56.200/32245.232.56.200 to 245.232.56.200—1
202245.232.56.201/32245.232.56.201 to 245.232.56.201—1
203245.232.56.202/32245.232.56.202 to 245.232.56.202—1
204245.232.56.203/32245.232.56.203 to 245.232.56.203—1
205245.232.56.204/32245.232.56.204 to 245.232.56.204—1
206245.232.56.205/32245.232.56.205 to 245.232.56.205—1
207245.232.56.206/32245.232.56.206 to 245.232.56.206—1
208245.232.56.207/32245.232.56.207 to 245.232.56.207—1
209245.232.56.208/32245.232.56.208 to 245.232.56.208—1
210245.232.56.209/32245.232.56.209 to 245.232.56.209—1
211245.232.56.210/32245.232.56.210 to 245.232.56.210—1
212245.232.56.211/32245.232.56.211 to 245.232.56.211—1
213245.232.56.212/32245.232.56.212 to 245.232.56.212—1
214245.232.56.213/32245.232.56.213 to 245.232.56.213—1
215245.232.56.214/32245.232.56.214 to 245.232.56.214—1
216245.232.56.215/32245.232.56.215 to 245.232.56.215—1
217245.232.56.216/32245.232.56.216 to 245.232.56.216—1
218245.232.56.217/32245.232.56.217 to 245.232.56.217—1
219245.232.56.218/32245.232.56.218 to 245.232.56.218—1
220245.232.56.219/32245.232.56.219 to 245.232.56.219—1
221245.232.56.220/32245.232.56.220 to 245.232.56.220—1
222245.232.56.221/32245.232.56.221 to 245.232.56.221—1
223245.232.56.222/32245.232.56.222 to 245.232.56.222—1
224245.232.56.223/32245.232.56.223 to 245.232.56.223—1
225245.232.56.224/32245.232.56.224 to 245.232.56.224—1
226245.232.56.225/32245.232.56.225 to 245.232.56.225—1
227245.232.56.226/32245.232.56.226 to 245.232.56.226—1
228245.232.56.227/32245.232.56.227 to 245.232.56.227—1
229245.232.56.228/32245.232.56.228 to 245.232.56.228—1
230245.232.56.229/32245.232.56.229 to 245.232.56.229—1
231245.232.56.230/32245.232.56.230 to 245.232.56.230—1
232245.232.56.231/32245.232.56.231 to 245.232.56.231—1
233245.232.56.232/32245.232.56.232 to 245.232.56.232—1
234245.232.56.233/32245.232.56.233 to 245.232.56.233—1
235245.232.56.234/32245.232.56.234 to 245.232.56.234—1
236245.232.56.235/32245.232.56.235 to 245.232.56.235—1
237245.232.56.236/32245.232.56.236 to 245.232.56.236—1
238245.232.56.237/32245.232.56.237 to 245.232.56.237—1
239245.232.56.238/32245.232.56.238 to 245.232.56.238—1
240245.232.56.239/32245.232.56.239 to 245.232.56.239—1
241245.232.56.240/32245.232.56.240 to 245.232.56.240—1
242245.232.56.241/32245.232.56.241 to 245.232.56.241—1
243245.232.56.242/32245.232.56.242 to 245.232.56.242—1
244245.232.56.243/32245.232.56.243 to 245.232.56.243—1
245245.232.56.244/32245.232.56.244 to 245.232.56.244—1
246245.232.56.245/32245.232.56.245 to 245.232.56.245—1
247245.232.56.246/32245.232.56.246 to 245.232.56.246—1
248245.232.56.247/32245.232.56.247 to 245.232.56.247—1
249245.232.56.248/32245.232.56.248 to 245.232.56.248—1
250245.232.56.249/32245.232.56.249 to 245.232.56.249—1
251245.232.56.250/32245.232.56.250 to 245.232.56.250—1
252245.232.56.251/32245.232.56.251 to 245.232.56.251—1
253245.232.56.252/32245.232.56.252 to 245.232.56.252—1
254245.232.56.253/32245.232.56.253 to 245.232.56.253—1
255245.232.56.254/32245.232.56.254 to 245.232.56.254—1
256245.232.56.255/32245.232.56.255 to 245.232.56.255—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.