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.

Network16.2.192.0/20
Usable hosts4,094
Subnet mask255.255.240.0
Addresses4,096
Network address
16.2.192.0
Broadcast address
16.2.207.255
First usable
16.2.192.1
Last usable
16.2.207.254
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 1002C000 · Integer 268615680 to 268619775
Reverse DNS zones
192.2.16.in-addr.arpa
193.2.16.in-addr.arpa
194.2.16.in-addr.arpa
195.2.16.in-addr.arpa
196.2.16.in-addr.arpa
197.2.16.in-addr.arpa
198.2.16.in-addr.arpa
199.2.16.in-addr.arpa
200.2.16.in-addr.arpa
201.2.16.in-addr.arpa
202.2.16.in-addr.arpa
203.2.16.in-addr.arpa
204.2.16.in-addr.arpa
205.2.16.in-addr.arpa
206.2.16.in-addr.arpa
207.2.16.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
Address00010000.00000010.11000000.0000000016.2.192.0
Subnet mask11111111.11111111.11110000.00000000255.255.240.0
Network00010000.00000010.11000000.0000000016.2.192.0
Broadcast00010000.00000010.11001111.1111111116.2.207.255
Split into smaller subnets/30
/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)

16.2.192.0/20 makes 1,024 subnets of /30; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
116.2.192.0/3016.2.192.1 to 16.2.192.216.2.192.32
216.2.192.4/3016.2.192.5 to 16.2.192.616.2.192.72
316.2.192.8/3016.2.192.9 to 16.2.192.1016.2.192.112
416.2.192.12/3016.2.192.13 to 16.2.192.1416.2.192.152
516.2.192.16/3016.2.192.17 to 16.2.192.1816.2.192.192
616.2.192.20/3016.2.192.21 to 16.2.192.2216.2.192.232
716.2.192.24/3016.2.192.25 to 16.2.192.2616.2.192.272
816.2.192.28/3016.2.192.29 to 16.2.192.3016.2.192.312
916.2.192.32/3016.2.192.33 to 16.2.192.3416.2.192.352
1016.2.192.36/3016.2.192.37 to 16.2.192.3816.2.192.392
1116.2.192.40/3016.2.192.41 to 16.2.192.4216.2.192.432
1216.2.192.44/3016.2.192.45 to 16.2.192.4616.2.192.472
1316.2.192.48/3016.2.192.49 to 16.2.192.5016.2.192.512
1416.2.192.52/3016.2.192.53 to 16.2.192.5416.2.192.552
1516.2.192.56/3016.2.192.57 to 16.2.192.5816.2.192.592
1616.2.192.60/3016.2.192.61 to 16.2.192.6216.2.192.632
1716.2.192.64/3016.2.192.65 to 16.2.192.6616.2.192.672
1816.2.192.68/3016.2.192.69 to 16.2.192.7016.2.192.712
1916.2.192.72/3016.2.192.73 to 16.2.192.7416.2.192.752
2016.2.192.76/3016.2.192.77 to 16.2.192.7816.2.192.792
2116.2.192.80/3016.2.192.81 to 16.2.192.8216.2.192.832
2216.2.192.84/3016.2.192.85 to 16.2.192.8616.2.192.872
2316.2.192.88/3016.2.192.89 to 16.2.192.9016.2.192.912
2416.2.192.92/3016.2.192.93 to 16.2.192.9416.2.192.952
2516.2.192.96/3016.2.192.97 to 16.2.192.9816.2.192.992
2616.2.192.100/3016.2.192.101 to 16.2.192.10216.2.192.1032
2716.2.192.104/3016.2.192.105 to 16.2.192.10616.2.192.1072
2816.2.192.108/3016.2.192.109 to 16.2.192.11016.2.192.1112
2916.2.192.112/3016.2.192.113 to 16.2.192.11416.2.192.1152
3016.2.192.116/3016.2.192.117 to 16.2.192.11816.2.192.1192
3116.2.192.120/3016.2.192.121 to 16.2.192.12216.2.192.1232
3216.2.192.124/3016.2.192.125 to 16.2.192.12616.2.192.1272
3316.2.192.128/3016.2.192.129 to 16.2.192.13016.2.192.1312
3416.2.192.132/3016.2.192.133 to 16.2.192.13416.2.192.1352
3516.2.192.136/3016.2.192.137 to 16.2.192.13816.2.192.1392
3616.2.192.140/3016.2.192.141 to 16.2.192.14216.2.192.1432
3716.2.192.144/3016.2.192.145 to 16.2.192.14616.2.192.1472
3816.2.192.148/3016.2.192.149 to 16.2.192.15016.2.192.1512
3916.2.192.152/3016.2.192.153 to 16.2.192.15416.2.192.1552
4016.2.192.156/3016.2.192.157 to 16.2.192.15816.2.192.1592
4116.2.192.160/3016.2.192.161 to 16.2.192.16216.2.192.1632
4216.2.192.164/3016.2.192.165 to 16.2.192.16616.2.192.1672
4316.2.192.168/3016.2.192.169 to 16.2.192.17016.2.192.1712
4416.2.192.172/3016.2.192.173 to 16.2.192.17416.2.192.1752
4516.2.192.176/3016.2.192.177 to 16.2.192.17816.2.192.1792
4616.2.192.180/3016.2.192.181 to 16.2.192.18216.2.192.1832
4716.2.192.184/3016.2.192.185 to 16.2.192.18616.2.192.1872
4816.2.192.188/3016.2.192.189 to 16.2.192.19016.2.192.1912
4916.2.192.192/3016.2.192.193 to 16.2.192.19416.2.192.1952
5016.2.192.196/3016.2.192.197 to 16.2.192.19816.2.192.1992
5116.2.192.200/3016.2.192.201 to 16.2.192.20216.2.192.2032
5216.2.192.204/3016.2.192.205 to 16.2.192.20616.2.192.2072
5316.2.192.208/3016.2.192.209 to 16.2.192.21016.2.192.2112
5416.2.192.212/3016.2.192.213 to 16.2.192.21416.2.192.2152
5516.2.192.216/3016.2.192.217 to 16.2.192.21816.2.192.2192
5616.2.192.220/3016.2.192.221 to 16.2.192.22216.2.192.2232
5716.2.192.224/3016.2.192.225 to 16.2.192.22616.2.192.2272
5816.2.192.228/3016.2.192.229 to 16.2.192.23016.2.192.2312
5916.2.192.232/3016.2.192.233 to 16.2.192.23416.2.192.2352
6016.2.192.236/3016.2.192.237 to 16.2.192.23816.2.192.2392
6116.2.192.240/3016.2.192.241 to 16.2.192.24216.2.192.2432
6216.2.192.244/3016.2.192.245 to 16.2.192.24616.2.192.2472
6316.2.192.248/3016.2.192.249 to 16.2.192.25016.2.192.2512
6416.2.192.252/3016.2.192.253 to 16.2.192.25416.2.192.2552
6516.2.193.0/3016.2.193.1 to 16.2.193.216.2.193.32
6616.2.193.4/3016.2.193.5 to 16.2.193.616.2.193.72
6716.2.193.8/3016.2.193.9 to 16.2.193.1016.2.193.112
6816.2.193.12/3016.2.193.13 to 16.2.193.1416.2.193.152
6916.2.193.16/3016.2.193.17 to 16.2.193.1816.2.193.192
7016.2.193.20/3016.2.193.21 to 16.2.193.2216.2.193.232
7116.2.193.24/3016.2.193.25 to 16.2.193.2616.2.193.272
7216.2.193.28/3016.2.193.29 to 16.2.193.3016.2.193.312
7316.2.193.32/3016.2.193.33 to 16.2.193.3416.2.193.352
7416.2.193.36/3016.2.193.37 to 16.2.193.3816.2.193.392
7516.2.193.40/3016.2.193.41 to 16.2.193.4216.2.193.432
7616.2.193.44/3016.2.193.45 to 16.2.193.4616.2.193.472
7716.2.193.48/3016.2.193.49 to 16.2.193.5016.2.193.512
7816.2.193.52/3016.2.193.53 to 16.2.193.5416.2.193.552
7916.2.193.56/3016.2.193.57 to 16.2.193.5816.2.193.592
8016.2.193.60/3016.2.193.61 to 16.2.193.6216.2.193.632
8116.2.193.64/3016.2.193.65 to 16.2.193.6616.2.193.672
8216.2.193.68/3016.2.193.69 to 16.2.193.7016.2.193.712
8316.2.193.72/3016.2.193.73 to 16.2.193.7416.2.193.752
8416.2.193.76/3016.2.193.77 to 16.2.193.7816.2.193.792
8516.2.193.80/3016.2.193.81 to 16.2.193.8216.2.193.832
8616.2.193.84/3016.2.193.85 to 16.2.193.8616.2.193.872
8716.2.193.88/3016.2.193.89 to 16.2.193.9016.2.193.912
8816.2.193.92/3016.2.193.93 to 16.2.193.9416.2.193.952
8916.2.193.96/3016.2.193.97 to 16.2.193.9816.2.193.992
9016.2.193.100/3016.2.193.101 to 16.2.193.10216.2.193.1032
9116.2.193.104/3016.2.193.105 to 16.2.193.10616.2.193.1072
9216.2.193.108/3016.2.193.109 to 16.2.193.11016.2.193.1112
9316.2.193.112/3016.2.193.113 to 16.2.193.11416.2.193.1152
9416.2.193.116/3016.2.193.117 to 16.2.193.11816.2.193.1192
9516.2.193.120/3016.2.193.121 to 16.2.193.12216.2.193.1232
9616.2.193.124/3016.2.193.125 to 16.2.193.12616.2.193.1272
9716.2.193.128/3016.2.193.129 to 16.2.193.13016.2.193.1312
9816.2.193.132/3016.2.193.133 to 16.2.193.13416.2.193.1352
9916.2.193.136/3016.2.193.137 to 16.2.193.13816.2.193.1392
10016.2.193.140/3016.2.193.141 to 16.2.193.14216.2.193.1432
10116.2.193.144/3016.2.193.145 to 16.2.193.14616.2.193.1472
10216.2.193.148/3016.2.193.149 to 16.2.193.15016.2.193.1512
10316.2.193.152/3016.2.193.153 to 16.2.193.15416.2.193.1552
10416.2.193.156/3016.2.193.157 to 16.2.193.15816.2.193.1592
10516.2.193.160/3016.2.193.161 to 16.2.193.16216.2.193.1632
10616.2.193.164/3016.2.193.165 to 16.2.193.16616.2.193.1672
10716.2.193.168/3016.2.193.169 to 16.2.193.17016.2.193.1712
10816.2.193.172/3016.2.193.173 to 16.2.193.17416.2.193.1752
10916.2.193.176/3016.2.193.177 to 16.2.193.17816.2.193.1792
11016.2.193.180/3016.2.193.181 to 16.2.193.18216.2.193.1832
11116.2.193.184/3016.2.193.185 to 16.2.193.18616.2.193.1872
11216.2.193.188/3016.2.193.189 to 16.2.193.19016.2.193.1912
11316.2.193.192/3016.2.193.193 to 16.2.193.19416.2.193.1952
11416.2.193.196/3016.2.193.197 to 16.2.193.19816.2.193.1992
11516.2.193.200/3016.2.193.201 to 16.2.193.20216.2.193.2032
11616.2.193.204/3016.2.193.205 to 16.2.193.20616.2.193.2072
11716.2.193.208/3016.2.193.209 to 16.2.193.21016.2.193.2112
11816.2.193.212/3016.2.193.213 to 16.2.193.21416.2.193.2152
11916.2.193.216/3016.2.193.217 to 16.2.193.21816.2.193.2192
12016.2.193.220/3016.2.193.221 to 16.2.193.22216.2.193.2232
12116.2.193.224/3016.2.193.225 to 16.2.193.22616.2.193.2272
12216.2.193.228/3016.2.193.229 to 16.2.193.23016.2.193.2312
12316.2.193.232/3016.2.193.233 to 16.2.193.23416.2.193.2352
12416.2.193.236/3016.2.193.237 to 16.2.193.23816.2.193.2392
12516.2.193.240/3016.2.193.241 to 16.2.193.24216.2.193.2432
12616.2.193.244/3016.2.193.245 to 16.2.193.24616.2.193.2472
12716.2.193.248/3016.2.193.249 to 16.2.193.25016.2.193.2512
12816.2.193.252/3016.2.193.253 to 16.2.193.25416.2.193.2552
12916.2.194.0/3016.2.194.1 to 16.2.194.216.2.194.32
13016.2.194.4/3016.2.194.5 to 16.2.194.616.2.194.72
13116.2.194.8/3016.2.194.9 to 16.2.194.1016.2.194.112
13216.2.194.12/3016.2.194.13 to 16.2.194.1416.2.194.152
13316.2.194.16/3016.2.194.17 to 16.2.194.1816.2.194.192
13416.2.194.20/3016.2.194.21 to 16.2.194.2216.2.194.232
13516.2.194.24/3016.2.194.25 to 16.2.194.2616.2.194.272
13616.2.194.28/3016.2.194.29 to 16.2.194.3016.2.194.312
13716.2.194.32/3016.2.194.33 to 16.2.194.3416.2.194.352
13816.2.194.36/3016.2.194.37 to 16.2.194.3816.2.194.392
13916.2.194.40/3016.2.194.41 to 16.2.194.4216.2.194.432
14016.2.194.44/3016.2.194.45 to 16.2.194.4616.2.194.472
14116.2.194.48/3016.2.194.49 to 16.2.194.5016.2.194.512
14216.2.194.52/3016.2.194.53 to 16.2.194.5416.2.194.552
14316.2.194.56/3016.2.194.57 to 16.2.194.5816.2.194.592
14416.2.194.60/3016.2.194.61 to 16.2.194.6216.2.194.632
14516.2.194.64/3016.2.194.65 to 16.2.194.6616.2.194.672
14616.2.194.68/3016.2.194.69 to 16.2.194.7016.2.194.712
14716.2.194.72/3016.2.194.73 to 16.2.194.7416.2.194.752
14816.2.194.76/3016.2.194.77 to 16.2.194.7816.2.194.792
14916.2.194.80/3016.2.194.81 to 16.2.194.8216.2.194.832
15016.2.194.84/3016.2.194.85 to 16.2.194.8616.2.194.872
15116.2.194.88/3016.2.194.89 to 16.2.194.9016.2.194.912
15216.2.194.92/3016.2.194.93 to 16.2.194.9416.2.194.952
15316.2.194.96/3016.2.194.97 to 16.2.194.9816.2.194.992
15416.2.194.100/3016.2.194.101 to 16.2.194.10216.2.194.1032
15516.2.194.104/3016.2.194.105 to 16.2.194.10616.2.194.1072
15616.2.194.108/3016.2.194.109 to 16.2.194.11016.2.194.1112
15716.2.194.112/3016.2.194.113 to 16.2.194.11416.2.194.1152
15816.2.194.116/3016.2.194.117 to 16.2.194.11816.2.194.1192
15916.2.194.120/3016.2.194.121 to 16.2.194.12216.2.194.1232
16016.2.194.124/3016.2.194.125 to 16.2.194.12616.2.194.1272
16116.2.194.128/3016.2.194.129 to 16.2.194.13016.2.194.1312
16216.2.194.132/3016.2.194.133 to 16.2.194.13416.2.194.1352
16316.2.194.136/3016.2.194.137 to 16.2.194.13816.2.194.1392
16416.2.194.140/3016.2.194.141 to 16.2.194.14216.2.194.1432
16516.2.194.144/3016.2.194.145 to 16.2.194.14616.2.194.1472
16616.2.194.148/3016.2.194.149 to 16.2.194.15016.2.194.1512
16716.2.194.152/3016.2.194.153 to 16.2.194.15416.2.194.1552
16816.2.194.156/3016.2.194.157 to 16.2.194.15816.2.194.1592
16916.2.194.160/3016.2.194.161 to 16.2.194.16216.2.194.1632
17016.2.194.164/3016.2.194.165 to 16.2.194.16616.2.194.1672
17116.2.194.168/3016.2.194.169 to 16.2.194.17016.2.194.1712
17216.2.194.172/3016.2.194.173 to 16.2.194.17416.2.194.1752
17316.2.194.176/3016.2.194.177 to 16.2.194.17816.2.194.1792
17416.2.194.180/3016.2.194.181 to 16.2.194.18216.2.194.1832
17516.2.194.184/3016.2.194.185 to 16.2.194.18616.2.194.1872
17616.2.194.188/3016.2.194.189 to 16.2.194.19016.2.194.1912
17716.2.194.192/3016.2.194.193 to 16.2.194.19416.2.194.1952
17816.2.194.196/3016.2.194.197 to 16.2.194.19816.2.194.1992
17916.2.194.200/3016.2.194.201 to 16.2.194.20216.2.194.2032
18016.2.194.204/3016.2.194.205 to 16.2.194.20616.2.194.2072
18116.2.194.208/3016.2.194.209 to 16.2.194.21016.2.194.2112
18216.2.194.212/3016.2.194.213 to 16.2.194.21416.2.194.2152
18316.2.194.216/3016.2.194.217 to 16.2.194.21816.2.194.2192
18416.2.194.220/3016.2.194.221 to 16.2.194.22216.2.194.2232
18516.2.194.224/3016.2.194.225 to 16.2.194.22616.2.194.2272
18616.2.194.228/3016.2.194.229 to 16.2.194.23016.2.194.2312
18716.2.194.232/3016.2.194.233 to 16.2.194.23416.2.194.2352
18816.2.194.236/3016.2.194.237 to 16.2.194.23816.2.194.2392
18916.2.194.240/3016.2.194.241 to 16.2.194.24216.2.194.2432
19016.2.194.244/3016.2.194.245 to 16.2.194.24616.2.194.2472
19116.2.194.248/3016.2.194.249 to 16.2.194.25016.2.194.2512
19216.2.194.252/3016.2.194.253 to 16.2.194.25416.2.194.2552
19316.2.195.0/3016.2.195.1 to 16.2.195.216.2.195.32
19416.2.195.4/3016.2.195.5 to 16.2.195.616.2.195.72
19516.2.195.8/3016.2.195.9 to 16.2.195.1016.2.195.112
19616.2.195.12/3016.2.195.13 to 16.2.195.1416.2.195.152
19716.2.195.16/3016.2.195.17 to 16.2.195.1816.2.195.192
19816.2.195.20/3016.2.195.21 to 16.2.195.2216.2.195.232
19916.2.195.24/3016.2.195.25 to 16.2.195.2616.2.195.272
20016.2.195.28/3016.2.195.29 to 16.2.195.3016.2.195.312
20116.2.195.32/3016.2.195.33 to 16.2.195.3416.2.195.352
20216.2.195.36/3016.2.195.37 to 16.2.195.3816.2.195.392
20316.2.195.40/3016.2.195.41 to 16.2.195.4216.2.195.432
20416.2.195.44/3016.2.195.45 to 16.2.195.4616.2.195.472
20516.2.195.48/3016.2.195.49 to 16.2.195.5016.2.195.512
20616.2.195.52/3016.2.195.53 to 16.2.195.5416.2.195.552
20716.2.195.56/3016.2.195.57 to 16.2.195.5816.2.195.592
20816.2.195.60/3016.2.195.61 to 16.2.195.6216.2.195.632
20916.2.195.64/3016.2.195.65 to 16.2.195.6616.2.195.672
21016.2.195.68/3016.2.195.69 to 16.2.195.7016.2.195.712
21116.2.195.72/3016.2.195.73 to 16.2.195.7416.2.195.752
21216.2.195.76/3016.2.195.77 to 16.2.195.7816.2.195.792
21316.2.195.80/3016.2.195.81 to 16.2.195.8216.2.195.832
21416.2.195.84/3016.2.195.85 to 16.2.195.8616.2.195.872
21516.2.195.88/3016.2.195.89 to 16.2.195.9016.2.195.912
21616.2.195.92/3016.2.195.93 to 16.2.195.9416.2.195.952
21716.2.195.96/3016.2.195.97 to 16.2.195.9816.2.195.992
21816.2.195.100/3016.2.195.101 to 16.2.195.10216.2.195.1032
21916.2.195.104/3016.2.195.105 to 16.2.195.10616.2.195.1072
22016.2.195.108/3016.2.195.109 to 16.2.195.11016.2.195.1112
22116.2.195.112/3016.2.195.113 to 16.2.195.11416.2.195.1152
22216.2.195.116/3016.2.195.117 to 16.2.195.11816.2.195.1192
22316.2.195.120/3016.2.195.121 to 16.2.195.12216.2.195.1232
22416.2.195.124/3016.2.195.125 to 16.2.195.12616.2.195.1272
22516.2.195.128/3016.2.195.129 to 16.2.195.13016.2.195.1312
22616.2.195.132/3016.2.195.133 to 16.2.195.13416.2.195.1352
22716.2.195.136/3016.2.195.137 to 16.2.195.13816.2.195.1392
22816.2.195.140/3016.2.195.141 to 16.2.195.14216.2.195.1432
22916.2.195.144/3016.2.195.145 to 16.2.195.14616.2.195.1472
23016.2.195.148/3016.2.195.149 to 16.2.195.15016.2.195.1512
23116.2.195.152/3016.2.195.153 to 16.2.195.15416.2.195.1552
23216.2.195.156/3016.2.195.157 to 16.2.195.15816.2.195.1592
23316.2.195.160/3016.2.195.161 to 16.2.195.16216.2.195.1632
23416.2.195.164/3016.2.195.165 to 16.2.195.16616.2.195.1672
23516.2.195.168/3016.2.195.169 to 16.2.195.17016.2.195.1712
23616.2.195.172/3016.2.195.173 to 16.2.195.17416.2.195.1752
23716.2.195.176/3016.2.195.177 to 16.2.195.17816.2.195.1792
23816.2.195.180/3016.2.195.181 to 16.2.195.18216.2.195.1832
23916.2.195.184/3016.2.195.185 to 16.2.195.18616.2.195.1872
24016.2.195.188/3016.2.195.189 to 16.2.195.19016.2.195.1912
24116.2.195.192/3016.2.195.193 to 16.2.195.19416.2.195.1952
24216.2.195.196/3016.2.195.197 to 16.2.195.19816.2.195.1992
24316.2.195.200/3016.2.195.201 to 16.2.195.20216.2.195.2032
24416.2.195.204/3016.2.195.205 to 16.2.195.20616.2.195.2072
24516.2.195.208/3016.2.195.209 to 16.2.195.21016.2.195.2112
24616.2.195.212/3016.2.195.213 to 16.2.195.21416.2.195.2152
24716.2.195.216/3016.2.195.217 to 16.2.195.21816.2.195.2192
24816.2.195.220/3016.2.195.221 to 16.2.195.22216.2.195.2232
24916.2.195.224/3016.2.195.225 to 16.2.195.22616.2.195.2272
25016.2.195.228/3016.2.195.229 to 16.2.195.23016.2.195.2312
25116.2.195.232/3016.2.195.233 to 16.2.195.23416.2.195.2352
25216.2.195.236/3016.2.195.237 to 16.2.195.23816.2.195.2392
25316.2.195.240/3016.2.195.241 to 16.2.195.24216.2.195.2432
25416.2.195.244/3016.2.195.245 to 16.2.195.24616.2.195.2472
25516.2.195.248/3016.2.195.249 to 16.2.195.25016.2.195.2512
25616.2.195.252/3016.2.195.253 to 16.2.195.25416.2.195.2552

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.