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.

Network15.3.100.0/22
Usable hosts1,022
Subnet mask255.255.252.0
Addresses1,024
Network address
15.3.100.0
Broadcast address
15.3.103.255
First usable
15.3.100.1
Last usable
15.3.103.254
Usable hosts
1,022 (1,024 less the network and broadcast addresses)
Subnet mask
255.255.252.0
Wildcard mask
0.0.3.255 (Cisco ACLs, OSPF)
Prefix length
/22
Type
Public public
Old class
A (default /8)
As numbers
Hex 0F036400 · Integer 251880448 to 251881471
Reverse DNS zones
100.3.15.in-addr.arpa
101.3.15.in-addr.arpa
102.3.15.in-addr.arpa
103.3.15.in-addr.arpa
/22 is not on a 8-bit boundary, so it takes 4 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00001111.00000011.01100100.0000000015.3.100.0
Subnet mask11111111.11111111.11111100.00000000255.255.252.0
Network00001111.00000011.01100100.0000000015.3.100.0
Broadcast00001111.00000011.01100111.1111111115.3.103.255
Split into smaller subnets/31
/23 (2)/24 (4)/25 (8)/26 (16)/27 (32)/28 (64)/29 (128)/30 (256)/31 (512)/32 (1,024)

15.3.100.0/22 makes 512 subnets of /31; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
115.3.100.0/3115.3.100.0 to 15.3.100.1—2
215.3.100.2/3115.3.100.2 to 15.3.100.3—2
315.3.100.4/3115.3.100.4 to 15.3.100.5—2
415.3.100.6/3115.3.100.6 to 15.3.100.7—2
515.3.100.8/3115.3.100.8 to 15.3.100.9—2
615.3.100.10/3115.3.100.10 to 15.3.100.11—2
715.3.100.12/3115.3.100.12 to 15.3.100.13—2
815.3.100.14/3115.3.100.14 to 15.3.100.15—2
915.3.100.16/3115.3.100.16 to 15.3.100.17—2
1015.3.100.18/3115.3.100.18 to 15.3.100.19—2
1115.3.100.20/3115.3.100.20 to 15.3.100.21—2
1215.3.100.22/3115.3.100.22 to 15.3.100.23—2
1315.3.100.24/3115.3.100.24 to 15.3.100.25—2
1415.3.100.26/3115.3.100.26 to 15.3.100.27—2
1515.3.100.28/3115.3.100.28 to 15.3.100.29—2
1615.3.100.30/3115.3.100.30 to 15.3.100.31—2
1715.3.100.32/3115.3.100.32 to 15.3.100.33—2
1815.3.100.34/3115.3.100.34 to 15.3.100.35—2
1915.3.100.36/3115.3.100.36 to 15.3.100.37—2
2015.3.100.38/3115.3.100.38 to 15.3.100.39—2
2115.3.100.40/3115.3.100.40 to 15.3.100.41—2
2215.3.100.42/3115.3.100.42 to 15.3.100.43—2
2315.3.100.44/3115.3.100.44 to 15.3.100.45—2
2415.3.100.46/3115.3.100.46 to 15.3.100.47—2
2515.3.100.48/3115.3.100.48 to 15.3.100.49—2
2615.3.100.50/3115.3.100.50 to 15.3.100.51—2
2715.3.100.52/3115.3.100.52 to 15.3.100.53—2
2815.3.100.54/3115.3.100.54 to 15.3.100.55—2
2915.3.100.56/3115.3.100.56 to 15.3.100.57—2
3015.3.100.58/3115.3.100.58 to 15.3.100.59—2
3115.3.100.60/3115.3.100.60 to 15.3.100.61—2
3215.3.100.62/3115.3.100.62 to 15.3.100.63—2
3315.3.100.64/3115.3.100.64 to 15.3.100.65—2
3415.3.100.66/3115.3.100.66 to 15.3.100.67—2
3515.3.100.68/3115.3.100.68 to 15.3.100.69—2
3615.3.100.70/3115.3.100.70 to 15.3.100.71—2
3715.3.100.72/3115.3.100.72 to 15.3.100.73—2
3815.3.100.74/3115.3.100.74 to 15.3.100.75—2
3915.3.100.76/3115.3.100.76 to 15.3.100.77—2
4015.3.100.78/3115.3.100.78 to 15.3.100.79—2
4115.3.100.80/3115.3.100.80 to 15.3.100.81—2
4215.3.100.82/3115.3.100.82 to 15.3.100.83—2
4315.3.100.84/3115.3.100.84 to 15.3.100.85—2
4415.3.100.86/3115.3.100.86 to 15.3.100.87—2
4515.3.100.88/3115.3.100.88 to 15.3.100.89—2
4615.3.100.90/3115.3.100.90 to 15.3.100.91—2
4715.3.100.92/3115.3.100.92 to 15.3.100.93—2
4815.3.100.94/3115.3.100.94 to 15.3.100.95—2
4915.3.100.96/3115.3.100.96 to 15.3.100.97—2
5015.3.100.98/3115.3.100.98 to 15.3.100.99—2
5115.3.100.100/3115.3.100.100 to 15.3.100.101—2
5215.3.100.102/3115.3.100.102 to 15.3.100.103—2
5315.3.100.104/3115.3.100.104 to 15.3.100.105—2
5415.3.100.106/3115.3.100.106 to 15.3.100.107—2
5515.3.100.108/3115.3.100.108 to 15.3.100.109—2
5615.3.100.110/3115.3.100.110 to 15.3.100.111—2
5715.3.100.112/3115.3.100.112 to 15.3.100.113—2
5815.3.100.114/3115.3.100.114 to 15.3.100.115—2
5915.3.100.116/3115.3.100.116 to 15.3.100.117—2
6015.3.100.118/3115.3.100.118 to 15.3.100.119—2
6115.3.100.120/3115.3.100.120 to 15.3.100.121—2
6215.3.100.122/3115.3.100.122 to 15.3.100.123—2
6315.3.100.124/3115.3.100.124 to 15.3.100.125—2
6415.3.100.126/3115.3.100.126 to 15.3.100.127—2
6515.3.100.128/3115.3.100.128 to 15.3.100.129—2
6615.3.100.130/3115.3.100.130 to 15.3.100.131—2
6715.3.100.132/3115.3.100.132 to 15.3.100.133—2
6815.3.100.134/3115.3.100.134 to 15.3.100.135—2
6915.3.100.136/3115.3.100.136 to 15.3.100.137—2
7015.3.100.138/3115.3.100.138 to 15.3.100.139—2
7115.3.100.140/3115.3.100.140 to 15.3.100.141—2
7215.3.100.142/3115.3.100.142 to 15.3.100.143—2
7315.3.100.144/3115.3.100.144 to 15.3.100.145—2
7415.3.100.146/3115.3.100.146 to 15.3.100.147—2
7515.3.100.148/3115.3.100.148 to 15.3.100.149—2
7615.3.100.150/3115.3.100.150 to 15.3.100.151—2
7715.3.100.152/3115.3.100.152 to 15.3.100.153—2
7815.3.100.154/3115.3.100.154 to 15.3.100.155—2
7915.3.100.156/3115.3.100.156 to 15.3.100.157—2
8015.3.100.158/3115.3.100.158 to 15.3.100.159—2
8115.3.100.160/3115.3.100.160 to 15.3.100.161—2
8215.3.100.162/3115.3.100.162 to 15.3.100.163—2
8315.3.100.164/3115.3.100.164 to 15.3.100.165—2
8415.3.100.166/3115.3.100.166 to 15.3.100.167—2
8515.3.100.168/3115.3.100.168 to 15.3.100.169—2
8615.3.100.170/3115.3.100.170 to 15.3.100.171—2
8715.3.100.172/3115.3.100.172 to 15.3.100.173—2
8815.3.100.174/3115.3.100.174 to 15.3.100.175—2
8915.3.100.176/3115.3.100.176 to 15.3.100.177—2
9015.3.100.178/3115.3.100.178 to 15.3.100.179—2
9115.3.100.180/3115.3.100.180 to 15.3.100.181—2
9215.3.100.182/3115.3.100.182 to 15.3.100.183—2
9315.3.100.184/3115.3.100.184 to 15.3.100.185—2
9415.3.100.186/3115.3.100.186 to 15.3.100.187—2
9515.3.100.188/3115.3.100.188 to 15.3.100.189—2
9615.3.100.190/3115.3.100.190 to 15.3.100.191—2
9715.3.100.192/3115.3.100.192 to 15.3.100.193—2
9815.3.100.194/3115.3.100.194 to 15.3.100.195—2
9915.3.100.196/3115.3.100.196 to 15.3.100.197—2
10015.3.100.198/3115.3.100.198 to 15.3.100.199—2
10115.3.100.200/3115.3.100.200 to 15.3.100.201—2
10215.3.100.202/3115.3.100.202 to 15.3.100.203—2
10315.3.100.204/3115.3.100.204 to 15.3.100.205—2
10415.3.100.206/3115.3.100.206 to 15.3.100.207—2
10515.3.100.208/3115.3.100.208 to 15.3.100.209—2
10615.3.100.210/3115.3.100.210 to 15.3.100.211—2
10715.3.100.212/3115.3.100.212 to 15.3.100.213—2
10815.3.100.214/3115.3.100.214 to 15.3.100.215—2
10915.3.100.216/3115.3.100.216 to 15.3.100.217—2
11015.3.100.218/3115.3.100.218 to 15.3.100.219—2
11115.3.100.220/3115.3.100.220 to 15.3.100.221—2
11215.3.100.222/3115.3.100.222 to 15.3.100.223—2
11315.3.100.224/3115.3.100.224 to 15.3.100.225—2
11415.3.100.226/3115.3.100.226 to 15.3.100.227—2
11515.3.100.228/3115.3.100.228 to 15.3.100.229—2
11615.3.100.230/3115.3.100.230 to 15.3.100.231—2
11715.3.100.232/3115.3.100.232 to 15.3.100.233—2
11815.3.100.234/3115.3.100.234 to 15.3.100.235—2
11915.3.100.236/3115.3.100.236 to 15.3.100.237—2
12015.3.100.238/3115.3.100.238 to 15.3.100.239—2
12115.3.100.240/3115.3.100.240 to 15.3.100.241—2
12215.3.100.242/3115.3.100.242 to 15.3.100.243—2
12315.3.100.244/3115.3.100.244 to 15.3.100.245—2
12415.3.100.246/3115.3.100.246 to 15.3.100.247—2
12515.3.100.248/3115.3.100.248 to 15.3.100.249—2
12615.3.100.250/3115.3.100.250 to 15.3.100.251—2
12715.3.100.252/3115.3.100.252 to 15.3.100.253—2
12815.3.100.254/3115.3.100.254 to 15.3.100.255—2
12915.3.101.0/3115.3.101.0 to 15.3.101.1—2
13015.3.101.2/3115.3.101.2 to 15.3.101.3—2
13115.3.101.4/3115.3.101.4 to 15.3.101.5—2
13215.3.101.6/3115.3.101.6 to 15.3.101.7—2
13315.3.101.8/3115.3.101.8 to 15.3.101.9—2
13415.3.101.10/3115.3.101.10 to 15.3.101.11—2
13515.3.101.12/3115.3.101.12 to 15.3.101.13—2
13615.3.101.14/3115.3.101.14 to 15.3.101.15—2
13715.3.101.16/3115.3.101.16 to 15.3.101.17—2
13815.3.101.18/3115.3.101.18 to 15.3.101.19—2
13915.3.101.20/3115.3.101.20 to 15.3.101.21—2
14015.3.101.22/3115.3.101.22 to 15.3.101.23—2
14115.3.101.24/3115.3.101.24 to 15.3.101.25—2
14215.3.101.26/3115.3.101.26 to 15.3.101.27—2
14315.3.101.28/3115.3.101.28 to 15.3.101.29—2
14415.3.101.30/3115.3.101.30 to 15.3.101.31—2
14515.3.101.32/3115.3.101.32 to 15.3.101.33—2
14615.3.101.34/3115.3.101.34 to 15.3.101.35—2
14715.3.101.36/3115.3.101.36 to 15.3.101.37—2
14815.3.101.38/3115.3.101.38 to 15.3.101.39—2
14915.3.101.40/3115.3.101.40 to 15.3.101.41—2
15015.3.101.42/3115.3.101.42 to 15.3.101.43—2
15115.3.101.44/3115.3.101.44 to 15.3.101.45—2
15215.3.101.46/3115.3.101.46 to 15.3.101.47—2
15315.3.101.48/3115.3.101.48 to 15.3.101.49—2
15415.3.101.50/3115.3.101.50 to 15.3.101.51—2
15515.3.101.52/3115.3.101.52 to 15.3.101.53—2
15615.3.101.54/3115.3.101.54 to 15.3.101.55—2
15715.3.101.56/3115.3.101.56 to 15.3.101.57—2
15815.3.101.58/3115.3.101.58 to 15.3.101.59—2
15915.3.101.60/3115.3.101.60 to 15.3.101.61—2
16015.3.101.62/3115.3.101.62 to 15.3.101.63—2
16115.3.101.64/3115.3.101.64 to 15.3.101.65—2
16215.3.101.66/3115.3.101.66 to 15.3.101.67—2
16315.3.101.68/3115.3.101.68 to 15.3.101.69—2
16415.3.101.70/3115.3.101.70 to 15.3.101.71—2
16515.3.101.72/3115.3.101.72 to 15.3.101.73—2
16615.3.101.74/3115.3.101.74 to 15.3.101.75—2
16715.3.101.76/3115.3.101.76 to 15.3.101.77—2
16815.3.101.78/3115.3.101.78 to 15.3.101.79—2
16915.3.101.80/3115.3.101.80 to 15.3.101.81—2
17015.3.101.82/3115.3.101.82 to 15.3.101.83—2
17115.3.101.84/3115.3.101.84 to 15.3.101.85—2
17215.3.101.86/3115.3.101.86 to 15.3.101.87—2
17315.3.101.88/3115.3.101.88 to 15.3.101.89—2
17415.3.101.90/3115.3.101.90 to 15.3.101.91—2
17515.3.101.92/3115.3.101.92 to 15.3.101.93—2
17615.3.101.94/3115.3.101.94 to 15.3.101.95—2
17715.3.101.96/3115.3.101.96 to 15.3.101.97—2
17815.3.101.98/3115.3.101.98 to 15.3.101.99—2
17915.3.101.100/3115.3.101.100 to 15.3.101.101—2
18015.3.101.102/3115.3.101.102 to 15.3.101.103—2
18115.3.101.104/3115.3.101.104 to 15.3.101.105—2
18215.3.101.106/3115.3.101.106 to 15.3.101.107—2
18315.3.101.108/3115.3.101.108 to 15.3.101.109—2
18415.3.101.110/3115.3.101.110 to 15.3.101.111—2
18515.3.101.112/3115.3.101.112 to 15.3.101.113—2
18615.3.101.114/3115.3.101.114 to 15.3.101.115—2
18715.3.101.116/3115.3.101.116 to 15.3.101.117—2
18815.3.101.118/3115.3.101.118 to 15.3.101.119—2
18915.3.101.120/3115.3.101.120 to 15.3.101.121—2
19015.3.101.122/3115.3.101.122 to 15.3.101.123—2
19115.3.101.124/3115.3.101.124 to 15.3.101.125—2
19215.3.101.126/3115.3.101.126 to 15.3.101.127—2
19315.3.101.128/3115.3.101.128 to 15.3.101.129—2
19415.3.101.130/3115.3.101.130 to 15.3.101.131—2
19515.3.101.132/3115.3.101.132 to 15.3.101.133—2
19615.3.101.134/3115.3.101.134 to 15.3.101.135—2
19715.3.101.136/3115.3.101.136 to 15.3.101.137—2
19815.3.101.138/3115.3.101.138 to 15.3.101.139—2
19915.3.101.140/3115.3.101.140 to 15.3.101.141—2
20015.3.101.142/3115.3.101.142 to 15.3.101.143—2
20115.3.101.144/3115.3.101.144 to 15.3.101.145—2
20215.3.101.146/3115.3.101.146 to 15.3.101.147—2
20315.3.101.148/3115.3.101.148 to 15.3.101.149—2
20415.3.101.150/3115.3.101.150 to 15.3.101.151—2
20515.3.101.152/3115.3.101.152 to 15.3.101.153—2
20615.3.101.154/3115.3.101.154 to 15.3.101.155—2
20715.3.101.156/3115.3.101.156 to 15.3.101.157—2
20815.3.101.158/3115.3.101.158 to 15.3.101.159—2
20915.3.101.160/3115.3.101.160 to 15.3.101.161—2
21015.3.101.162/3115.3.101.162 to 15.3.101.163—2
21115.3.101.164/3115.3.101.164 to 15.3.101.165—2
21215.3.101.166/3115.3.101.166 to 15.3.101.167—2
21315.3.101.168/3115.3.101.168 to 15.3.101.169—2
21415.3.101.170/3115.3.101.170 to 15.3.101.171—2
21515.3.101.172/3115.3.101.172 to 15.3.101.173—2
21615.3.101.174/3115.3.101.174 to 15.3.101.175—2
21715.3.101.176/3115.3.101.176 to 15.3.101.177—2
21815.3.101.178/3115.3.101.178 to 15.3.101.179—2
21915.3.101.180/3115.3.101.180 to 15.3.101.181—2
22015.3.101.182/3115.3.101.182 to 15.3.101.183—2
22115.3.101.184/3115.3.101.184 to 15.3.101.185—2
22215.3.101.186/3115.3.101.186 to 15.3.101.187—2
22315.3.101.188/3115.3.101.188 to 15.3.101.189—2
22415.3.101.190/3115.3.101.190 to 15.3.101.191—2
22515.3.101.192/3115.3.101.192 to 15.3.101.193—2
22615.3.101.194/3115.3.101.194 to 15.3.101.195—2
22715.3.101.196/3115.3.101.196 to 15.3.101.197—2
22815.3.101.198/3115.3.101.198 to 15.3.101.199—2
22915.3.101.200/3115.3.101.200 to 15.3.101.201—2
23015.3.101.202/3115.3.101.202 to 15.3.101.203—2
23115.3.101.204/3115.3.101.204 to 15.3.101.205—2
23215.3.101.206/3115.3.101.206 to 15.3.101.207—2
23315.3.101.208/3115.3.101.208 to 15.3.101.209—2
23415.3.101.210/3115.3.101.210 to 15.3.101.211—2
23515.3.101.212/3115.3.101.212 to 15.3.101.213—2
23615.3.101.214/3115.3.101.214 to 15.3.101.215—2
23715.3.101.216/3115.3.101.216 to 15.3.101.217—2
23815.3.101.218/3115.3.101.218 to 15.3.101.219—2
23915.3.101.220/3115.3.101.220 to 15.3.101.221—2
24015.3.101.222/3115.3.101.222 to 15.3.101.223—2
24115.3.101.224/3115.3.101.224 to 15.3.101.225—2
24215.3.101.226/3115.3.101.226 to 15.3.101.227—2
24315.3.101.228/3115.3.101.228 to 15.3.101.229—2
24415.3.101.230/3115.3.101.230 to 15.3.101.231—2
24515.3.101.232/3115.3.101.232 to 15.3.101.233—2
24615.3.101.234/3115.3.101.234 to 15.3.101.235—2
24715.3.101.236/3115.3.101.236 to 15.3.101.237—2
24815.3.101.238/3115.3.101.238 to 15.3.101.239—2
24915.3.101.240/3115.3.101.240 to 15.3.101.241—2
25015.3.101.242/3115.3.101.242 to 15.3.101.243—2
25115.3.101.244/3115.3.101.244 to 15.3.101.245—2
25215.3.101.246/3115.3.101.246 to 15.3.101.247—2
25315.3.101.248/3115.3.101.248 to 15.3.101.249—2
25415.3.101.250/3115.3.101.250 to 15.3.101.251—2
25515.3.101.252/3115.3.101.252 to 15.3.101.253—2
25615.3.101.254/3115.3.101.254 to 15.3.101.255—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.