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.

Network38.128.0.0/9
Usable hosts8,388,606
Subnet mask255.128.0.0
Addresses8,388,608
Network address
38.128.0.0
Broadcast address
38.255.255.255
First usable
38.128.0.1
Last usable
38.255.255.254
Usable hosts
8,388,606 (8,388,608 less the network and broadcast addresses)
Subnet mask
255.128.0.0
Wildcard mask
0.127.255.255 (Cisco ACLs, OSPF)
Prefix length
/9
Type
Public public
Old class
A (default /8)
As numbers
Hex 26800000 · Integer 645922816 to 654311423
Reverse DNS zones
128.38.in-addr.arpa
129.38.in-addr.arpa
130.38.in-addr.arpa
131.38.in-addr.arpa
132.38.in-addr.arpa
133.38.in-addr.arpa
134.38.in-addr.arpa
135.38.in-addr.arpa
136.38.in-addr.arpa
137.38.in-addr.arpa
138.38.in-addr.arpa
139.38.in-addr.arpa
140.38.in-addr.arpa
141.38.in-addr.arpa
142.38.in-addr.arpa
143.38.in-addr.arpa
and 112 more
/9 is not on a 8-bit boundary, so it takes 128 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00100110.10000000.00000000.0000000038.128.0.0
Subnet mask11111111.10000000.00000000.00000000255.128.0.0
Network00100110.10000000.00000000.0000000038.128.0.0
Broadcast00100110.11111111.11111111.1111111138.255.255.255
Split into smaller subnets/19
/10 (2)/11 (4)/12 (8)/13 (16)/14 (32)/15 (64)/16 (128)/17 (256)/18 (512)/19 (1,024)/20 (2,048)/21 (4,096)

38.128.0.0/9 makes 1,024 subnets of /19; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
138.128.0.0/1938.128.0.1 to 38.128.31.25438.128.31.2558,190
238.128.32.0/1938.128.32.1 to 38.128.63.25438.128.63.2558,190
338.128.64.0/1938.128.64.1 to 38.128.95.25438.128.95.2558,190
438.128.96.0/1938.128.96.1 to 38.128.127.25438.128.127.2558,190
538.128.128.0/1938.128.128.1 to 38.128.159.25438.128.159.2558,190
638.128.160.0/1938.128.160.1 to 38.128.191.25438.128.191.2558,190
738.128.192.0/1938.128.192.1 to 38.128.223.25438.128.223.2558,190
838.128.224.0/1938.128.224.1 to 38.128.255.25438.128.255.2558,190
938.129.0.0/1938.129.0.1 to 38.129.31.25438.129.31.2558,190
1038.129.32.0/1938.129.32.1 to 38.129.63.25438.129.63.2558,190
1138.129.64.0/1938.129.64.1 to 38.129.95.25438.129.95.2558,190
1238.129.96.0/1938.129.96.1 to 38.129.127.25438.129.127.2558,190
1338.129.128.0/1938.129.128.1 to 38.129.159.25438.129.159.2558,190
1438.129.160.0/1938.129.160.1 to 38.129.191.25438.129.191.2558,190
1538.129.192.0/1938.129.192.1 to 38.129.223.25438.129.223.2558,190
1638.129.224.0/1938.129.224.1 to 38.129.255.25438.129.255.2558,190
1738.130.0.0/1938.130.0.1 to 38.130.31.25438.130.31.2558,190
1838.130.32.0/1938.130.32.1 to 38.130.63.25438.130.63.2558,190
1938.130.64.0/1938.130.64.1 to 38.130.95.25438.130.95.2558,190
2038.130.96.0/1938.130.96.1 to 38.130.127.25438.130.127.2558,190
2138.130.128.0/1938.130.128.1 to 38.130.159.25438.130.159.2558,190
2238.130.160.0/1938.130.160.1 to 38.130.191.25438.130.191.2558,190
2338.130.192.0/1938.130.192.1 to 38.130.223.25438.130.223.2558,190
2438.130.224.0/1938.130.224.1 to 38.130.255.25438.130.255.2558,190
2538.131.0.0/1938.131.0.1 to 38.131.31.25438.131.31.2558,190
2638.131.32.0/1938.131.32.1 to 38.131.63.25438.131.63.2558,190
2738.131.64.0/1938.131.64.1 to 38.131.95.25438.131.95.2558,190
2838.131.96.0/1938.131.96.1 to 38.131.127.25438.131.127.2558,190
2938.131.128.0/1938.131.128.1 to 38.131.159.25438.131.159.2558,190
3038.131.160.0/1938.131.160.1 to 38.131.191.25438.131.191.2558,190
3138.131.192.0/1938.131.192.1 to 38.131.223.25438.131.223.2558,190
3238.131.224.0/1938.131.224.1 to 38.131.255.25438.131.255.2558,190
3338.132.0.0/1938.132.0.1 to 38.132.31.25438.132.31.2558,190
3438.132.32.0/1938.132.32.1 to 38.132.63.25438.132.63.2558,190
3538.132.64.0/1938.132.64.1 to 38.132.95.25438.132.95.2558,190
3638.132.96.0/1938.132.96.1 to 38.132.127.25438.132.127.2558,190
3738.132.128.0/1938.132.128.1 to 38.132.159.25438.132.159.2558,190
3838.132.160.0/1938.132.160.1 to 38.132.191.25438.132.191.2558,190
3938.132.192.0/1938.132.192.1 to 38.132.223.25438.132.223.2558,190
4038.132.224.0/1938.132.224.1 to 38.132.255.25438.132.255.2558,190
4138.133.0.0/1938.133.0.1 to 38.133.31.25438.133.31.2558,190
4238.133.32.0/1938.133.32.1 to 38.133.63.25438.133.63.2558,190
4338.133.64.0/1938.133.64.1 to 38.133.95.25438.133.95.2558,190
4438.133.96.0/1938.133.96.1 to 38.133.127.25438.133.127.2558,190
4538.133.128.0/1938.133.128.1 to 38.133.159.25438.133.159.2558,190
4638.133.160.0/1938.133.160.1 to 38.133.191.25438.133.191.2558,190
4738.133.192.0/1938.133.192.1 to 38.133.223.25438.133.223.2558,190
4838.133.224.0/1938.133.224.1 to 38.133.255.25438.133.255.2558,190
4938.134.0.0/1938.134.0.1 to 38.134.31.25438.134.31.2558,190
5038.134.32.0/1938.134.32.1 to 38.134.63.25438.134.63.2558,190
5138.134.64.0/1938.134.64.1 to 38.134.95.25438.134.95.2558,190
5238.134.96.0/1938.134.96.1 to 38.134.127.25438.134.127.2558,190
5338.134.128.0/1938.134.128.1 to 38.134.159.25438.134.159.2558,190
5438.134.160.0/1938.134.160.1 to 38.134.191.25438.134.191.2558,190
5538.134.192.0/1938.134.192.1 to 38.134.223.25438.134.223.2558,190
5638.134.224.0/1938.134.224.1 to 38.134.255.25438.134.255.2558,190
5738.135.0.0/1938.135.0.1 to 38.135.31.25438.135.31.2558,190
5838.135.32.0/1938.135.32.1 to 38.135.63.25438.135.63.2558,190
5938.135.64.0/1938.135.64.1 to 38.135.95.25438.135.95.2558,190
6038.135.96.0/1938.135.96.1 to 38.135.127.25438.135.127.2558,190
6138.135.128.0/1938.135.128.1 to 38.135.159.25438.135.159.2558,190
6238.135.160.0/1938.135.160.1 to 38.135.191.25438.135.191.2558,190
6338.135.192.0/1938.135.192.1 to 38.135.223.25438.135.223.2558,190
6438.135.224.0/1938.135.224.1 to 38.135.255.25438.135.255.2558,190
6538.136.0.0/1938.136.0.1 to 38.136.31.25438.136.31.2558,190
6638.136.32.0/1938.136.32.1 to 38.136.63.25438.136.63.2558,190
6738.136.64.0/1938.136.64.1 to 38.136.95.25438.136.95.2558,190
6838.136.96.0/1938.136.96.1 to 38.136.127.25438.136.127.2558,190
6938.136.128.0/1938.136.128.1 to 38.136.159.25438.136.159.2558,190
7038.136.160.0/1938.136.160.1 to 38.136.191.25438.136.191.2558,190
7138.136.192.0/1938.136.192.1 to 38.136.223.25438.136.223.2558,190
7238.136.224.0/1938.136.224.1 to 38.136.255.25438.136.255.2558,190
7338.137.0.0/1938.137.0.1 to 38.137.31.25438.137.31.2558,190
7438.137.32.0/1938.137.32.1 to 38.137.63.25438.137.63.2558,190
7538.137.64.0/1938.137.64.1 to 38.137.95.25438.137.95.2558,190
7638.137.96.0/1938.137.96.1 to 38.137.127.25438.137.127.2558,190
7738.137.128.0/1938.137.128.1 to 38.137.159.25438.137.159.2558,190
7838.137.160.0/1938.137.160.1 to 38.137.191.25438.137.191.2558,190
7938.137.192.0/1938.137.192.1 to 38.137.223.25438.137.223.2558,190
8038.137.224.0/1938.137.224.1 to 38.137.255.25438.137.255.2558,190
8138.138.0.0/1938.138.0.1 to 38.138.31.25438.138.31.2558,190
8238.138.32.0/1938.138.32.1 to 38.138.63.25438.138.63.2558,190
8338.138.64.0/1938.138.64.1 to 38.138.95.25438.138.95.2558,190
8438.138.96.0/1938.138.96.1 to 38.138.127.25438.138.127.2558,190
8538.138.128.0/1938.138.128.1 to 38.138.159.25438.138.159.2558,190
8638.138.160.0/1938.138.160.1 to 38.138.191.25438.138.191.2558,190
8738.138.192.0/1938.138.192.1 to 38.138.223.25438.138.223.2558,190
8838.138.224.0/1938.138.224.1 to 38.138.255.25438.138.255.2558,190
8938.139.0.0/1938.139.0.1 to 38.139.31.25438.139.31.2558,190
9038.139.32.0/1938.139.32.1 to 38.139.63.25438.139.63.2558,190
9138.139.64.0/1938.139.64.1 to 38.139.95.25438.139.95.2558,190
9238.139.96.0/1938.139.96.1 to 38.139.127.25438.139.127.2558,190
9338.139.128.0/1938.139.128.1 to 38.139.159.25438.139.159.2558,190
9438.139.160.0/1938.139.160.1 to 38.139.191.25438.139.191.2558,190
9538.139.192.0/1938.139.192.1 to 38.139.223.25438.139.223.2558,190
9638.139.224.0/1938.139.224.1 to 38.139.255.25438.139.255.2558,190
9738.140.0.0/1938.140.0.1 to 38.140.31.25438.140.31.2558,190
9838.140.32.0/1938.140.32.1 to 38.140.63.25438.140.63.2558,190
9938.140.64.0/1938.140.64.1 to 38.140.95.25438.140.95.2558,190
10038.140.96.0/1938.140.96.1 to 38.140.127.25438.140.127.2558,190
10138.140.128.0/1938.140.128.1 to 38.140.159.25438.140.159.2558,190
10238.140.160.0/1938.140.160.1 to 38.140.191.25438.140.191.2558,190
10338.140.192.0/1938.140.192.1 to 38.140.223.25438.140.223.2558,190
10438.140.224.0/1938.140.224.1 to 38.140.255.25438.140.255.2558,190
10538.141.0.0/1938.141.0.1 to 38.141.31.25438.141.31.2558,190
10638.141.32.0/1938.141.32.1 to 38.141.63.25438.141.63.2558,190
10738.141.64.0/1938.141.64.1 to 38.141.95.25438.141.95.2558,190
10838.141.96.0/1938.141.96.1 to 38.141.127.25438.141.127.2558,190
10938.141.128.0/1938.141.128.1 to 38.141.159.25438.141.159.2558,190
11038.141.160.0/1938.141.160.1 to 38.141.191.25438.141.191.2558,190
11138.141.192.0/1938.141.192.1 to 38.141.223.25438.141.223.2558,190
11238.141.224.0/1938.141.224.1 to 38.141.255.25438.141.255.2558,190
11338.142.0.0/1938.142.0.1 to 38.142.31.25438.142.31.2558,190
11438.142.32.0/1938.142.32.1 to 38.142.63.25438.142.63.2558,190
11538.142.64.0/1938.142.64.1 to 38.142.95.25438.142.95.2558,190
11638.142.96.0/1938.142.96.1 to 38.142.127.25438.142.127.2558,190
11738.142.128.0/1938.142.128.1 to 38.142.159.25438.142.159.2558,190
11838.142.160.0/1938.142.160.1 to 38.142.191.25438.142.191.2558,190
11938.142.192.0/1938.142.192.1 to 38.142.223.25438.142.223.2558,190
12038.142.224.0/1938.142.224.1 to 38.142.255.25438.142.255.2558,190
12138.143.0.0/1938.143.0.1 to 38.143.31.25438.143.31.2558,190
12238.143.32.0/1938.143.32.1 to 38.143.63.25438.143.63.2558,190
12338.143.64.0/1938.143.64.1 to 38.143.95.25438.143.95.2558,190
12438.143.96.0/1938.143.96.1 to 38.143.127.25438.143.127.2558,190
12538.143.128.0/1938.143.128.1 to 38.143.159.25438.143.159.2558,190
12638.143.160.0/1938.143.160.1 to 38.143.191.25438.143.191.2558,190
12738.143.192.0/1938.143.192.1 to 38.143.223.25438.143.223.2558,190
12838.143.224.0/1938.143.224.1 to 38.143.255.25438.143.255.2558,190
12938.144.0.0/1938.144.0.1 to 38.144.31.25438.144.31.2558,190
13038.144.32.0/1938.144.32.1 to 38.144.63.25438.144.63.2558,190
13138.144.64.0/1938.144.64.1 to 38.144.95.25438.144.95.2558,190
13238.144.96.0/1938.144.96.1 to 38.144.127.25438.144.127.2558,190
13338.144.128.0/1938.144.128.1 to 38.144.159.25438.144.159.2558,190
13438.144.160.0/1938.144.160.1 to 38.144.191.25438.144.191.2558,190
13538.144.192.0/1938.144.192.1 to 38.144.223.25438.144.223.2558,190
13638.144.224.0/1938.144.224.1 to 38.144.255.25438.144.255.2558,190
13738.145.0.0/1938.145.0.1 to 38.145.31.25438.145.31.2558,190
13838.145.32.0/1938.145.32.1 to 38.145.63.25438.145.63.2558,190
13938.145.64.0/1938.145.64.1 to 38.145.95.25438.145.95.2558,190
14038.145.96.0/1938.145.96.1 to 38.145.127.25438.145.127.2558,190
14138.145.128.0/1938.145.128.1 to 38.145.159.25438.145.159.2558,190
14238.145.160.0/1938.145.160.1 to 38.145.191.25438.145.191.2558,190
14338.145.192.0/1938.145.192.1 to 38.145.223.25438.145.223.2558,190
14438.145.224.0/1938.145.224.1 to 38.145.255.25438.145.255.2558,190
14538.146.0.0/1938.146.0.1 to 38.146.31.25438.146.31.2558,190
14638.146.32.0/1938.146.32.1 to 38.146.63.25438.146.63.2558,190
14738.146.64.0/1938.146.64.1 to 38.146.95.25438.146.95.2558,190
14838.146.96.0/1938.146.96.1 to 38.146.127.25438.146.127.2558,190
14938.146.128.0/1938.146.128.1 to 38.146.159.25438.146.159.2558,190
15038.146.160.0/1938.146.160.1 to 38.146.191.25438.146.191.2558,190
15138.146.192.0/1938.146.192.1 to 38.146.223.25438.146.223.2558,190
15238.146.224.0/1938.146.224.1 to 38.146.255.25438.146.255.2558,190
15338.147.0.0/1938.147.0.1 to 38.147.31.25438.147.31.2558,190
15438.147.32.0/1938.147.32.1 to 38.147.63.25438.147.63.2558,190
15538.147.64.0/1938.147.64.1 to 38.147.95.25438.147.95.2558,190
15638.147.96.0/1938.147.96.1 to 38.147.127.25438.147.127.2558,190
15738.147.128.0/1938.147.128.1 to 38.147.159.25438.147.159.2558,190
15838.147.160.0/1938.147.160.1 to 38.147.191.25438.147.191.2558,190
15938.147.192.0/1938.147.192.1 to 38.147.223.25438.147.223.2558,190
16038.147.224.0/1938.147.224.1 to 38.147.255.25438.147.255.2558,190
16138.148.0.0/1938.148.0.1 to 38.148.31.25438.148.31.2558,190
16238.148.32.0/1938.148.32.1 to 38.148.63.25438.148.63.2558,190
16338.148.64.0/1938.148.64.1 to 38.148.95.25438.148.95.2558,190
16438.148.96.0/1938.148.96.1 to 38.148.127.25438.148.127.2558,190
16538.148.128.0/1938.148.128.1 to 38.148.159.25438.148.159.2558,190
16638.148.160.0/1938.148.160.1 to 38.148.191.25438.148.191.2558,190
16738.148.192.0/1938.148.192.1 to 38.148.223.25438.148.223.2558,190
16838.148.224.0/1938.148.224.1 to 38.148.255.25438.148.255.2558,190
16938.149.0.0/1938.149.0.1 to 38.149.31.25438.149.31.2558,190
17038.149.32.0/1938.149.32.1 to 38.149.63.25438.149.63.2558,190
17138.149.64.0/1938.149.64.1 to 38.149.95.25438.149.95.2558,190
17238.149.96.0/1938.149.96.1 to 38.149.127.25438.149.127.2558,190
17338.149.128.0/1938.149.128.1 to 38.149.159.25438.149.159.2558,190
17438.149.160.0/1938.149.160.1 to 38.149.191.25438.149.191.2558,190
17538.149.192.0/1938.149.192.1 to 38.149.223.25438.149.223.2558,190
17638.149.224.0/1938.149.224.1 to 38.149.255.25438.149.255.2558,190
17738.150.0.0/1938.150.0.1 to 38.150.31.25438.150.31.2558,190
17838.150.32.0/1938.150.32.1 to 38.150.63.25438.150.63.2558,190
17938.150.64.0/1938.150.64.1 to 38.150.95.25438.150.95.2558,190
18038.150.96.0/1938.150.96.1 to 38.150.127.25438.150.127.2558,190
18138.150.128.0/1938.150.128.1 to 38.150.159.25438.150.159.2558,190
18238.150.160.0/1938.150.160.1 to 38.150.191.25438.150.191.2558,190
18338.150.192.0/1938.150.192.1 to 38.150.223.25438.150.223.2558,190
18438.150.224.0/1938.150.224.1 to 38.150.255.25438.150.255.2558,190
18538.151.0.0/1938.151.0.1 to 38.151.31.25438.151.31.2558,190
18638.151.32.0/1938.151.32.1 to 38.151.63.25438.151.63.2558,190
18738.151.64.0/1938.151.64.1 to 38.151.95.25438.151.95.2558,190
18838.151.96.0/1938.151.96.1 to 38.151.127.25438.151.127.2558,190
18938.151.128.0/1938.151.128.1 to 38.151.159.25438.151.159.2558,190
19038.151.160.0/1938.151.160.1 to 38.151.191.25438.151.191.2558,190
19138.151.192.0/1938.151.192.1 to 38.151.223.25438.151.223.2558,190
19238.151.224.0/1938.151.224.1 to 38.151.255.25438.151.255.2558,190
19338.152.0.0/1938.152.0.1 to 38.152.31.25438.152.31.2558,190
19438.152.32.0/1938.152.32.1 to 38.152.63.25438.152.63.2558,190
19538.152.64.0/1938.152.64.1 to 38.152.95.25438.152.95.2558,190
19638.152.96.0/1938.152.96.1 to 38.152.127.25438.152.127.2558,190
19738.152.128.0/1938.152.128.1 to 38.152.159.25438.152.159.2558,190
19838.152.160.0/1938.152.160.1 to 38.152.191.25438.152.191.2558,190
19938.152.192.0/1938.152.192.1 to 38.152.223.25438.152.223.2558,190
20038.152.224.0/1938.152.224.1 to 38.152.255.25438.152.255.2558,190
20138.153.0.0/1938.153.0.1 to 38.153.31.25438.153.31.2558,190
20238.153.32.0/1938.153.32.1 to 38.153.63.25438.153.63.2558,190
20338.153.64.0/1938.153.64.1 to 38.153.95.25438.153.95.2558,190
20438.153.96.0/1938.153.96.1 to 38.153.127.25438.153.127.2558,190
20538.153.128.0/1938.153.128.1 to 38.153.159.25438.153.159.2558,190
20638.153.160.0/1938.153.160.1 to 38.153.191.25438.153.191.2558,190
20738.153.192.0/1938.153.192.1 to 38.153.223.25438.153.223.2558,190
20838.153.224.0/1938.153.224.1 to 38.153.255.25438.153.255.2558,190
20938.154.0.0/1938.154.0.1 to 38.154.31.25438.154.31.2558,190
21038.154.32.0/1938.154.32.1 to 38.154.63.25438.154.63.2558,190
21138.154.64.0/1938.154.64.1 to 38.154.95.25438.154.95.2558,190
21238.154.96.0/1938.154.96.1 to 38.154.127.25438.154.127.2558,190
21338.154.128.0/1938.154.128.1 to 38.154.159.25438.154.159.2558,190
21438.154.160.0/1938.154.160.1 to 38.154.191.25438.154.191.2558,190
21538.154.192.0/1938.154.192.1 to 38.154.223.25438.154.223.2558,190
21638.154.224.0/1938.154.224.1 to 38.154.255.25438.154.255.2558,190
21738.155.0.0/1938.155.0.1 to 38.155.31.25438.155.31.2558,190
21838.155.32.0/1938.155.32.1 to 38.155.63.25438.155.63.2558,190
21938.155.64.0/1938.155.64.1 to 38.155.95.25438.155.95.2558,190
22038.155.96.0/1938.155.96.1 to 38.155.127.25438.155.127.2558,190
22138.155.128.0/1938.155.128.1 to 38.155.159.25438.155.159.2558,190
22238.155.160.0/1938.155.160.1 to 38.155.191.25438.155.191.2558,190
22338.155.192.0/1938.155.192.1 to 38.155.223.25438.155.223.2558,190
22438.155.224.0/1938.155.224.1 to 38.155.255.25438.155.255.2558,190
22538.156.0.0/1938.156.0.1 to 38.156.31.25438.156.31.2558,190
22638.156.32.0/1938.156.32.1 to 38.156.63.25438.156.63.2558,190
22738.156.64.0/1938.156.64.1 to 38.156.95.25438.156.95.2558,190
22838.156.96.0/1938.156.96.1 to 38.156.127.25438.156.127.2558,190
22938.156.128.0/1938.156.128.1 to 38.156.159.25438.156.159.2558,190
23038.156.160.0/1938.156.160.1 to 38.156.191.25438.156.191.2558,190
23138.156.192.0/1938.156.192.1 to 38.156.223.25438.156.223.2558,190
23238.156.224.0/1938.156.224.1 to 38.156.255.25438.156.255.2558,190
23338.157.0.0/1938.157.0.1 to 38.157.31.25438.157.31.2558,190
23438.157.32.0/1938.157.32.1 to 38.157.63.25438.157.63.2558,190
23538.157.64.0/1938.157.64.1 to 38.157.95.25438.157.95.2558,190
23638.157.96.0/1938.157.96.1 to 38.157.127.25438.157.127.2558,190
23738.157.128.0/1938.157.128.1 to 38.157.159.25438.157.159.2558,190
23838.157.160.0/1938.157.160.1 to 38.157.191.25438.157.191.2558,190
23938.157.192.0/1938.157.192.1 to 38.157.223.25438.157.223.2558,190
24038.157.224.0/1938.157.224.1 to 38.157.255.25438.157.255.2558,190
24138.158.0.0/1938.158.0.1 to 38.158.31.25438.158.31.2558,190
24238.158.32.0/1938.158.32.1 to 38.158.63.25438.158.63.2558,190
24338.158.64.0/1938.158.64.1 to 38.158.95.25438.158.95.2558,190
24438.158.96.0/1938.158.96.1 to 38.158.127.25438.158.127.2558,190
24538.158.128.0/1938.158.128.1 to 38.158.159.25438.158.159.2558,190
24638.158.160.0/1938.158.160.1 to 38.158.191.25438.158.191.2558,190
24738.158.192.0/1938.158.192.1 to 38.158.223.25438.158.223.2558,190
24838.158.224.0/1938.158.224.1 to 38.158.255.25438.158.255.2558,190
24938.159.0.0/1938.159.0.1 to 38.159.31.25438.159.31.2558,190
25038.159.32.0/1938.159.32.1 to 38.159.63.25438.159.63.2558,190
25138.159.64.0/1938.159.64.1 to 38.159.95.25438.159.95.2558,190
25238.159.96.0/1938.159.96.1 to 38.159.127.25438.159.127.2558,190
25338.159.128.0/1938.159.128.1 to 38.159.159.25438.159.159.2558,190
25438.159.160.0/1938.159.160.1 to 38.159.191.25438.159.191.2558,190
25538.159.192.0/1938.159.192.1 to 38.159.223.25438.159.223.2558,190
25638.159.224.0/1938.159.224.1 to 38.159.255.25438.159.255.2558,190

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.