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.

Network108.2.32.0/20
Usable hosts4,094
Subnet mask255.255.240.0
Addresses4,096
Network address
108.2.32.0
Broadcast address
108.2.47.255
First usable
108.2.32.1
Last usable
108.2.47.254
Usable hosts
4,094 (4,096 less the network and broadcast addresses)
Subnet mask
255.255.240.0
Wildcard mask
0.0.15.255 (Cisco ACLs, OSPF)
Prefix length
/20
Type
Public public
Old class
A (default /8)
As numbers
Hex 6C022000 · Integer 1812078592 to 1812082687
Reverse DNS zones
32.2.108.in-addr.arpa
33.2.108.in-addr.arpa
34.2.108.in-addr.arpa
35.2.108.in-addr.arpa
36.2.108.in-addr.arpa
37.2.108.in-addr.arpa
38.2.108.in-addr.arpa
39.2.108.in-addr.arpa
40.2.108.in-addr.arpa
41.2.108.in-addr.arpa
42.2.108.in-addr.arpa
43.2.108.in-addr.arpa
44.2.108.in-addr.arpa
45.2.108.in-addr.arpa
46.2.108.in-addr.arpa
47.2.108.in-addr.arpa
/20 is not on a 8-bit boundary, so it takes 16 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address01101100.00000010.00100000.00000000108.2.32.0
Subnet mask11111111.11111111.11110000.00000000255.255.240.0
Network01101100.00000010.00100000.00000000108.2.32.0
Broadcast01101100.00000010.00101111.11111111108.2.47.255
Split into smaller subnets/31
/21 (2)/22 (4)/23 (8)/24 (16)/25 (32)/26 (64)/27 (128)/28 (256)/29 (512)/30 (1,024)/31 (2,048)/32 (4,096)

108.2.32.0/20 makes 2,048 subnets of /31; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1108.2.32.0/31108.2.32.0 to 108.2.32.1—2
2108.2.32.2/31108.2.32.2 to 108.2.32.3—2
3108.2.32.4/31108.2.32.4 to 108.2.32.5—2
4108.2.32.6/31108.2.32.6 to 108.2.32.7—2
5108.2.32.8/31108.2.32.8 to 108.2.32.9—2
6108.2.32.10/31108.2.32.10 to 108.2.32.11—2
7108.2.32.12/31108.2.32.12 to 108.2.32.13—2
8108.2.32.14/31108.2.32.14 to 108.2.32.15—2
9108.2.32.16/31108.2.32.16 to 108.2.32.17—2
10108.2.32.18/31108.2.32.18 to 108.2.32.19—2
11108.2.32.20/31108.2.32.20 to 108.2.32.21—2
12108.2.32.22/31108.2.32.22 to 108.2.32.23—2
13108.2.32.24/31108.2.32.24 to 108.2.32.25—2
14108.2.32.26/31108.2.32.26 to 108.2.32.27—2
15108.2.32.28/31108.2.32.28 to 108.2.32.29—2
16108.2.32.30/31108.2.32.30 to 108.2.32.31—2
17108.2.32.32/31108.2.32.32 to 108.2.32.33—2
18108.2.32.34/31108.2.32.34 to 108.2.32.35—2
19108.2.32.36/31108.2.32.36 to 108.2.32.37—2
20108.2.32.38/31108.2.32.38 to 108.2.32.39—2
21108.2.32.40/31108.2.32.40 to 108.2.32.41—2
22108.2.32.42/31108.2.32.42 to 108.2.32.43—2
23108.2.32.44/31108.2.32.44 to 108.2.32.45—2
24108.2.32.46/31108.2.32.46 to 108.2.32.47—2
25108.2.32.48/31108.2.32.48 to 108.2.32.49—2
26108.2.32.50/31108.2.32.50 to 108.2.32.51—2
27108.2.32.52/31108.2.32.52 to 108.2.32.53—2
28108.2.32.54/31108.2.32.54 to 108.2.32.55—2
29108.2.32.56/31108.2.32.56 to 108.2.32.57—2
30108.2.32.58/31108.2.32.58 to 108.2.32.59—2
31108.2.32.60/31108.2.32.60 to 108.2.32.61—2
32108.2.32.62/31108.2.32.62 to 108.2.32.63—2
33108.2.32.64/31108.2.32.64 to 108.2.32.65—2
34108.2.32.66/31108.2.32.66 to 108.2.32.67—2
35108.2.32.68/31108.2.32.68 to 108.2.32.69—2
36108.2.32.70/31108.2.32.70 to 108.2.32.71—2
37108.2.32.72/31108.2.32.72 to 108.2.32.73—2
38108.2.32.74/31108.2.32.74 to 108.2.32.75—2
39108.2.32.76/31108.2.32.76 to 108.2.32.77—2
40108.2.32.78/31108.2.32.78 to 108.2.32.79—2
41108.2.32.80/31108.2.32.80 to 108.2.32.81—2
42108.2.32.82/31108.2.32.82 to 108.2.32.83—2
43108.2.32.84/31108.2.32.84 to 108.2.32.85—2
44108.2.32.86/31108.2.32.86 to 108.2.32.87—2
45108.2.32.88/31108.2.32.88 to 108.2.32.89—2
46108.2.32.90/31108.2.32.90 to 108.2.32.91—2
47108.2.32.92/31108.2.32.92 to 108.2.32.93—2
48108.2.32.94/31108.2.32.94 to 108.2.32.95—2
49108.2.32.96/31108.2.32.96 to 108.2.32.97—2
50108.2.32.98/31108.2.32.98 to 108.2.32.99—2
51108.2.32.100/31108.2.32.100 to 108.2.32.101—2
52108.2.32.102/31108.2.32.102 to 108.2.32.103—2
53108.2.32.104/31108.2.32.104 to 108.2.32.105—2
54108.2.32.106/31108.2.32.106 to 108.2.32.107—2
55108.2.32.108/31108.2.32.108 to 108.2.32.109—2
56108.2.32.110/31108.2.32.110 to 108.2.32.111—2
57108.2.32.112/31108.2.32.112 to 108.2.32.113—2
58108.2.32.114/31108.2.32.114 to 108.2.32.115—2
59108.2.32.116/31108.2.32.116 to 108.2.32.117—2
60108.2.32.118/31108.2.32.118 to 108.2.32.119—2
61108.2.32.120/31108.2.32.120 to 108.2.32.121—2
62108.2.32.122/31108.2.32.122 to 108.2.32.123—2
63108.2.32.124/31108.2.32.124 to 108.2.32.125—2
64108.2.32.126/31108.2.32.126 to 108.2.32.127—2
65108.2.32.128/31108.2.32.128 to 108.2.32.129—2
66108.2.32.130/31108.2.32.130 to 108.2.32.131—2
67108.2.32.132/31108.2.32.132 to 108.2.32.133—2
68108.2.32.134/31108.2.32.134 to 108.2.32.135—2
69108.2.32.136/31108.2.32.136 to 108.2.32.137—2
70108.2.32.138/31108.2.32.138 to 108.2.32.139—2
71108.2.32.140/31108.2.32.140 to 108.2.32.141—2
72108.2.32.142/31108.2.32.142 to 108.2.32.143—2
73108.2.32.144/31108.2.32.144 to 108.2.32.145—2
74108.2.32.146/31108.2.32.146 to 108.2.32.147—2
75108.2.32.148/31108.2.32.148 to 108.2.32.149—2
76108.2.32.150/31108.2.32.150 to 108.2.32.151—2
77108.2.32.152/31108.2.32.152 to 108.2.32.153—2
78108.2.32.154/31108.2.32.154 to 108.2.32.155—2
79108.2.32.156/31108.2.32.156 to 108.2.32.157—2
80108.2.32.158/31108.2.32.158 to 108.2.32.159—2
81108.2.32.160/31108.2.32.160 to 108.2.32.161—2
82108.2.32.162/31108.2.32.162 to 108.2.32.163—2
83108.2.32.164/31108.2.32.164 to 108.2.32.165—2
84108.2.32.166/31108.2.32.166 to 108.2.32.167—2
85108.2.32.168/31108.2.32.168 to 108.2.32.169—2
86108.2.32.170/31108.2.32.170 to 108.2.32.171—2
87108.2.32.172/31108.2.32.172 to 108.2.32.173—2
88108.2.32.174/31108.2.32.174 to 108.2.32.175—2
89108.2.32.176/31108.2.32.176 to 108.2.32.177—2
90108.2.32.178/31108.2.32.178 to 108.2.32.179—2
91108.2.32.180/31108.2.32.180 to 108.2.32.181—2
92108.2.32.182/31108.2.32.182 to 108.2.32.183—2
93108.2.32.184/31108.2.32.184 to 108.2.32.185—2
94108.2.32.186/31108.2.32.186 to 108.2.32.187—2
95108.2.32.188/31108.2.32.188 to 108.2.32.189—2
96108.2.32.190/31108.2.32.190 to 108.2.32.191—2
97108.2.32.192/31108.2.32.192 to 108.2.32.193—2
98108.2.32.194/31108.2.32.194 to 108.2.32.195—2
99108.2.32.196/31108.2.32.196 to 108.2.32.197—2
100108.2.32.198/31108.2.32.198 to 108.2.32.199—2
101108.2.32.200/31108.2.32.200 to 108.2.32.201—2
102108.2.32.202/31108.2.32.202 to 108.2.32.203—2
103108.2.32.204/31108.2.32.204 to 108.2.32.205—2
104108.2.32.206/31108.2.32.206 to 108.2.32.207—2
105108.2.32.208/31108.2.32.208 to 108.2.32.209—2
106108.2.32.210/31108.2.32.210 to 108.2.32.211—2
107108.2.32.212/31108.2.32.212 to 108.2.32.213—2
108108.2.32.214/31108.2.32.214 to 108.2.32.215—2
109108.2.32.216/31108.2.32.216 to 108.2.32.217—2
110108.2.32.218/31108.2.32.218 to 108.2.32.219—2
111108.2.32.220/31108.2.32.220 to 108.2.32.221—2
112108.2.32.222/31108.2.32.222 to 108.2.32.223—2
113108.2.32.224/31108.2.32.224 to 108.2.32.225—2
114108.2.32.226/31108.2.32.226 to 108.2.32.227—2
115108.2.32.228/31108.2.32.228 to 108.2.32.229—2
116108.2.32.230/31108.2.32.230 to 108.2.32.231—2
117108.2.32.232/31108.2.32.232 to 108.2.32.233—2
118108.2.32.234/31108.2.32.234 to 108.2.32.235—2
119108.2.32.236/31108.2.32.236 to 108.2.32.237—2
120108.2.32.238/31108.2.32.238 to 108.2.32.239—2
121108.2.32.240/31108.2.32.240 to 108.2.32.241—2
122108.2.32.242/31108.2.32.242 to 108.2.32.243—2
123108.2.32.244/31108.2.32.244 to 108.2.32.245—2
124108.2.32.246/31108.2.32.246 to 108.2.32.247—2
125108.2.32.248/31108.2.32.248 to 108.2.32.249—2
126108.2.32.250/31108.2.32.250 to 108.2.32.251—2
127108.2.32.252/31108.2.32.252 to 108.2.32.253—2
128108.2.32.254/31108.2.32.254 to 108.2.32.255—2
129108.2.33.0/31108.2.33.0 to 108.2.33.1—2
130108.2.33.2/31108.2.33.2 to 108.2.33.3—2
131108.2.33.4/31108.2.33.4 to 108.2.33.5—2
132108.2.33.6/31108.2.33.6 to 108.2.33.7—2
133108.2.33.8/31108.2.33.8 to 108.2.33.9—2
134108.2.33.10/31108.2.33.10 to 108.2.33.11—2
135108.2.33.12/31108.2.33.12 to 108.2.33.13—2
136108.2.33.14/31108.2.33.14 to 108.2.33.15—2
137108.2.33.16/31108.2.33.16 to 108.2.33.17—2
138108.2.33.18/31108.2.33.18 to 108.2.33.19—2
139108.2.33.20/31108.2.33.20 to 108.2.33.21—2
140108.2.33.22/31108.2.33.22 to 108.2.33.23—2
141108.2.33.24/31108.2.33.24 to 108.2.33.25—2
142108.2.33.26/31108.2.33.26 to 108.2.33.27—2
143108.2.33.28/31108.2.33.28 to 108.2.33.29—2
144108.2.33.30/31108.2.33.30 to 108.2.33.31—2
145108.2.33.32/31108.2.33.32 to 108.2.33.33—2
146108.2.33.34/31108.2.33.34 to 108.2.33.35—2
147108.2.33.36/31108.2.33.36 to 108.2.33.37—2
148108.2.33.38/31108.2.33.38 to 108.2.33.39—2
149108.2.33.40/31108.2.33.40 to 108.2.33.41—2
150108.2.33.42/31108.2.33.42 to 108.2.33.43—2
151108.2.33.44/31108.2.33.44 to 108.2.33.45—2
152108.2.33.46/31108.2.33.46 to 108.2.33.47—2
153108.2.33.48/31108.2.33.48 to 108.2.33.49—2
154108.2.33.50/31108.2.33.50 to 108.2.33.51—2
155108.2.33.52/31108.2.33.52 to 108.2.33.53—2
156108.2.33.54/31108.2.33.54 to 108.2.33.55—2
157108.2.33.56/31108.2.33.56 to 108.2.33.57—2
158108.2.33.58/31108.2.33.58 to 108.2.33.59—2
159108.2.33.60/31108.2.33.60 to 108.2.33.61—2
160108.2.33.62/31108.2.33.62 to 108.2.33.63—2
161108.2.33.64/31108.2.33.64 to 108.2.33.65—2
162108.2.33.66/31108.2.33.66 to 108.2.33.67—2
163108.2.33.68/31108.2.33.68 to 108.2.33.69—2
164108.2.33.70/31108.2.33.70 to 108.2.33.71—2
165108.2.33.72/31108.2.33.72 to 108.2.33.73—2
166108.2.33.74/31108.2.33.74 to 108.2.33.75—2
167108.2.33.76/31108.2.33.76 to 108.2.33.77—2
168108.2.33.78/31108.2.33.78 to 108.2.33.79—2
169108.2.33.80/31108.2.33.80 to 108.2.33.81—2
170108.2.33.82/31108.2.33.82 to 108.2.33.83—2
171108.2.33.84/31108.2.33.84 to 108.2.33.85—2
172108.2.33.86/31108.2.33.86 to 108.2.33.87—2
173108.2.33.88/31108.2.33.88 to 108.2.33.89—2
174108.2.33.90/31108.2.33.90 to 108.2.33.91—2
175108.2.33.92/31108.2.33.92 to 108.2.33.93—2
176108.2.33.94/31108.2.33.94 to 108.2.33.95—2
177108.2.33.96/31108.2.33.96 to 108.2.33.97—2
178108.2.33.98/31108.2.33.98 to 108.2.33.99—2
179108.2.33.100/31108.2.33.100 to 108.2.33.101—2
180108.2.33.102/31108.2.33.102 to 108.2.33.103—2
181108.2.33.104/31108.2.33.104 to 108.2.33.105—2
182108.2.33.106/31108.2.33.106 to 108.2.33.107—2
183108.2.33.108/31108.2.33.108 to 108.2.33.109—2
184108.2.33.110/31108.2.33.110 to 108.2.33.111—2
185108.2.33.112/31108.2.33.112 to 108.2.33.113—2
186108.2.33.114/31108.2.33.114 to 108.2.33.115—2
187108.2.33.116/31108.2.33.116 to 108.2.33.117—2
188108.2.33.118/31108.2.33.118 to 108.2.33.119—2
189108.2.33.120/31108.2.33.120 to 108.2.33.121—2
190108.2.33.122/31108.2.33.122 to 108.2.33.123—2
191108.2.33.124/31108.2.33.124 to 108.2.33.125—2
192108.2.33.126/31108.2.33.126 to 108.2.33.127—2
193108.2.33.128/31108.2.33.128 to 108.2.33.129—2
194108.2.33.130/31108.2.33.130 to 108.2.33.131—2
195108.2.33.132/31108.2.33.132 to 108.2.33.133—2
196108.2.33.134/31108.2.33.134 to 108.2.33.135—2
197108.2.33.136/31108.2.33.136 to 108.2.33.137—2
198108.2.33.138/31108.2.33.138 to 108.2.33.139—2
199108.2.33.140/31108.2.33.140 to 108.2.33.141—2
200108.2.33.142/31108.2.33.142 to 108.2.33.143—2
201108.2.33.144/31108.2.33.144 to 108.2.33.145—2
202108.2.33.146/31108.2.33.146 to 108.2.33.147—2
203108.2.33.148/31108.2.33.148 to 108.2.33.149—2
204108.2.33.150/31108.2.33.150 to 108.2.33.151—2
205108.2.33.152/31108.2.33.152 to 108.2.33.153—2
206108.2.33.154/31108.2.33.154 to 108.2.33.155—2
207108.2.33.156/31108.2.33.156 to 108.2.33.157—2
208108.2.33.158/31108.2.33.158 to 108.2.33.159—2
209108.2.33.160/31108.2.33.160 to 108.2.33.161—2
210108.2.33.162/31108.2.33.162 to 108.2.33.163—2
211108.2.33.164/31108.2.33.164 to 108.2.33.165—2
212108.2.33.166/31108.2.33.166 to 108.2.33.167—2
213108.2.33.168/31108.2.33.168 to 108.2.33.169—2
214108.2.33.170/31108.2.33.170 to 108.2.33.171—2
215108.2.33.172/31108.2.33.172 to 108.2.33.173—2
216108.2.33.174/31108.2.33.174 to 108.2.33.175—2
217108.2.33.176/31108.2.33.176 to 108.2.33.177—2
218108.2.33.178/31108.2.33.178 to 108.2.33.179—2
219108.2.33.180/31108.2.33.180 to 108.2.33.181—2
220108.2.33.182/31108.2.33.182 to 108.2.33.183—2
221108.2.33.184/31108.2.33.184 to 108.2.33.185—2
222108.2.33.186/31108.2.33.186 to 108.2.33.187—2
223108.2.33.188/31108.2.33.188 to 108.2.33.189—2
224108.2.33.190/31108.2.33.190 to 108.2.33.191—2
225108.2.33.192/31108.2.33.192 to 108.2.33.193—2
226108.2.33.194/31108.2.33.194 to 108.2.33.195—2
227108.2.33.196/31108.2.33.196 to 108.2.33.197—2
228108.2.33.198/31108.2.33.198 to 108.2.33.199—2
229108.2.33.200/31108.2.33.200 to 108.2.33.201—2
230108.2.33.202/31108.2.33.202 to 108.2.33.203—2
231108.2.33.204/31108.2.33.204 to 108.2.33.205—2
232108.2.33.206/31108.2.33.206 to 108.2.33.207—2
233108.2.33.208/31108.2.33.208 to 108.2.33.209—2
234108.2.33.210/31108.2.33.210 to 108.2.33.211—2
235108.2.33.212/31108.2.33.212 to 108.2.33.213—2
236108.2.33.214/31108.2.33.214 to 108.2.33.215—2
237108.2.33.216/31108.2.33.216 to 108.2.33.217—2
238108.2.33.218/31108.2.33.218 to 108.2.33.219—2
239108.2.33.220/31108.2.33.220 to 108.2.33.221—2
240108.2.33.222/31108.2.33.222 to 108.2.33.223—2
241108.2.33.224/31108.2.33.224 to 108.2.33.225—2
242108.2.33.226/31108.2.33.226 to 108.2.33.227—2
243108.2.33.228/31108.2.33.228 to 108.2.33.229—2
244108.2.33.230/31108.2.33.230 to 108.2.33.231—2
245108.2.33.232/31108.2.33.232 to 108.2.33.233—2
246108.2.33.234/31108.2.33.234 to 108.2.33.235—2
247108.2.33.236/31108.2.33.236 to 108.2.33.237—2
248108.2.33.238/31108.2.33.238 to 108.2.33.239—2
249108.2.33.240/31108.2.33.240 to 108.2.33.241—2
250108.2.33.242/31108.2.33.242 to 108.2.33.243—2
251108.2.33.244/31108.2.33.244 to 108.2.33.245—2
252108.2.33.246/31108.2.33.246 to 108.2.33.247—2
253108.2.33.248/31108.2.33.248 to 108.2.33.249—2
254108.2.33.250/31108.2.33.250 to 108.2.33.251—2
255108.2.33.252/31108.2.33.252 to 108.2.33.253—2
256108.2.33.254/31108.2.33.254 to 108.2.33.255—2

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.