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.

Network42.78.0.0/17
Usable hosts32,766
Subnet mask255.255.128.0
Addresses32,768
Network address
42.78.0.0
Broadcast address
42.78.127.255
First usable
42.78.0.1
Last usable
42.78.127.254
Usable hosts
32,766 (32,768 less the network and broadcast addresses)
Subnet mask
255.255.128.0
Wildcard mask
0.0.127.255 (Cisco ACLs, OSPF)
Prefix length
/17
Type
Public public
Old class
A (default /8)
As numbers
Hex 2A4E0000 · Integer 709754880 to 709787647
Reverse DNS zones
0.78.42.in-addr.arpa
1.78.42.in-addr.arpa
2.78.42.in-addr.arpa
3.78.42.in-addr.arpa
4.78.42.in-addr.arpa
5.78.42.in-addr.arpa
6.78.42.in-addr.arpa
7.78.42.in-addr.arpa
8.78.42.in-addr.arpa
9.78.42.in-addr.arpa
10.78.42.in-addr.arpa
11.78.42.in-addr.arpa
12.78.42.in-addr.arpa
13.78.42.in-addr.arpa
14.78.42.in-addr.arpa
15.78.42.in-addr.arpa
and 112 more
/17 is not on a 8-bit boundary, so it takes 128 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00101010.01001110.00000000.0000000042.78.0.0
Subnet mask11111111.11111111.10000000.00000000255.255.128.0
Network00101010.01001110.00000000.0000000042.78.0.0
Broadcast00101010.01001110.01111111.1111111142.78.127.255
Split into smaller subnets/28
/18 (2)/19 (4)/20 (8)/21 (16)/22 (32)/23 (64)/24 (128)/25 (256)/26 (512)/27 (1,024)/28 (2,048)/29 (4,096)

42.78.0.0/17 makes 2,048 subnets of /28; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
142.78.0.0/2842.78.0.1 to 42.78.0.1442.78.0.1514
242.78.0.16/2842.78.0.17 to 42.78.0.3042.78.0.3114
342.78.0.32/2842.78.0.33 to 42.78.0.4642.78.0.4714
442.78.0.48/2842.78.0.49 to 42.78.0.6242.78.0.6314
542.78.0.64/2842.78.0.65 to 42.78.0.7842.78.0.7914
642.78.0.80/2842.78.0.81 to 42.78.0.9442.78.0.9514
742.78.0.96/2842.78.0.97 to 42.78.0.11042.78.0.11114
842.78.0.112/2842.78.0.113 to 42.78.0.12642.78.0.12714
942.78.0.128/2842.78.0.129 to 42.78.0.14242.78.0.14314
1042.78.0.144/2842.78.0.145 to 42.78.0.15842.78.0.15914
1142.78.0.160/2842.78.0.161 to 42.78.0.17442.78.0.17514
1242.78.0.176/2842.78.0.177 to 42.78.0.19042.78.0.19114
1342.78.0.192/2842.78.0.193 to 42.78.0.20642.78.0.20714
1442.78.0.208/2842.78.0.209 to 42.78.0.22242.78.0.22314
1542.78.0.224/2842.78.0.225 to 42.78.0.23842.78.0.23914
1642.78.0.240/2842.78.0.241 to 42.78.0.25442.78.0.25514
1742.78.1.0/2842.78.1.1 to 42.78.1.1442.78.1.1514
1842.78.1.16/2842.78.1.17 to 42.78.1.3042.78.1.3114
1942.78.1.32/2842.78.1.33 to 42.78.1.4642.78.1.4714
2042.78.1.48/2842.78.1.49 to 42.78.1.6242.78.1.6314
2142.78.1.64/2842.78.1.65 to 42.78.1.7842.78.1.7914
2242.78.1.80/2842.78.1.81 to 42.78.1.9442.78.1.9514
2342.78.1.96/2842.78.1.97 to 42.78.1.11042.78.1.11114
2442.78.1.112/2842.78.1.113 to 42.78.1.12642.78.1.12714
2542.78.1.128/2842.78.1.129 to 42.78.1.14242.78.1.14314
2642.78.1.144/2842.78.1.145 to 42.78.1.15842.78.1.15914
2742.78.1.160/2842.78.1.161 to 42.78.1.17442.78.1.17514
2842.78.1.176/2842.78.1.177 to 42.78.1.19042.78.1.19114
2942.78.1.192/2842.78.1.193 to 42.78.1.20642.78.1.20714
3042.78.1.208/2842.78.1.209 to 42.78.1.22242.78.1.22314
3142.78.1.224/2842.78.1.225 to 42.78.1.23842.78.1.23914
3242.78.1.240/2842.78.1.241 to 42.78.1.25442.78.1.25514
3342.78.2.0/2842.78.2.1 to 42.78.2.1442.78.2.1514
3442.78.2.16/2842.78.2.17 to 42.78.2.3042.78.2.3114
3542.78.2.32/2842.78.2.33 to 42.78.2.4642.78.2.4714
3642.78.2.48/2842.78.2.49 to 42.78.2.6242.78.2.6314
3742.78.2.64/2842.78.2.65 to 42.78.2.7842.78.2.7914
3842.78.2.80/2842.78.2.81 to 42.78.2.9442.78.2.9514
3942.78.2.96/2842.78.2.97 to 42.78.2.11042.78.2.11114
4042.78.2.112/2842.78.2.113 to 42.78.2.12642.78.2.12714
4142.78.2.128/2842.78.2.129 to 42.78.2.14242.78.2.14314
4242.78.2.144/2842.78.2.145 to 42.78.2.15842.78.2.15914
4342.78.2.160/2842.78.2.161 to 42.78.2.17442.78.2.17514
4442.78.2.176/2842.78.2.177 to 42.78.2.19042.78.2.19114
4542.78.2.192/2842.78.2.193 to 42.78.2.20642.78.2.20714
4642.78.2.208/2842.78.2.209 to 42.78.2.22242.78.2.22314
4742.78.2.224/2842.78.2.225 to 42.78.2.23842.78.2.23914
4842.78.2.240/2842.78.2.241 to 42.78.2.25442.78.2.25514
4942.78.3.0/2842.78.3.1 to 42.78.3.1442.78.3.1514
5042.78.3.16/2842.78.3.17 to 42.78.3.3042.78.3.3114
5142.78.3.32/2842.78.3.33 to 42.78.3.4642.78.3.4714
5242.78.3.48/2842.78.3.49 to 42.78.3.6242.78.3.6314
5342.78.3.64/2842.78.3.65 to 42.78.3.7842.78.3.7914
5442.78.3.80/2842.78.3.81 to 42.78.3.9442.78.3.9514
5542.78.3.96/2842.78.3.97 to 42.78.3.11042.78.3.11114
5642.78.3.112/2842.78.3.113 to 42.78.3.12642.78.3.12714
5742.78.3.128/2842.78.3.129 to 42.78.3.14242.78.3.14314
5842.78.3.144/2842.78.3.145 to 42.78.3.15842.78.3.15914
5942.78.3.160/2842.78.3.161 to 42.78.3.17442.78.3.17514
6042.78.3.176/2842.78.3.177 to 42.78.3.19042.78.3.19114
6142.78.3.192/2842.78.3.193 to 42.78.3.20642.78.3.20714
6242.78.3.208/2842.78.3.209 to 42.78.3.22242.78.3.22314
6342.78.3.224/2842.78.3.225 to 42.78.3.23842.78.3.23914
6442.78.3.240/2842.78.3.241 to 42.78.3.25442.78.3.25514
6542.78.4.0/2842.78.4.1 to 42.78.4.1442.78.4.1514
6642.78.4.16/2842.78.4.17 to 42.78.4.3042.78.4.3114
6742.78.4.32/2842.78.4.33 to 42.78.4.4642.78.4.4714
6842.78.4.48/2842.78.4.49 to 42.78.4.6242.78.4.6314
6942.78.4.64/2842.78.4.65 to 42.78.4.7842.78.4.7914
7042.78.4.80/2842.78.4.81 to 42.78.4.9442.78.4.9514
7142.78.4.96/2842.78.4.97 to 42.78.4.11042.78.4.11114
7242.78.4.112/2842.78.4.113 to 42.78.4.12642.78.4.12714
7342.78.4.128/2842.78.4.129 to 42.78.4.14242.78.4.14314
7442.78.4.144/2842.78.4.145 to 42.78.4.15842.78.4.15914
7542.78.4.160/2842.78.4.161 to 42.78.4.17442.78.4.17514
7642.78.4.176/2842.78.4.177 to 42.78.4.19042.78.4.19114
7742.78.4.192/2842.78.4.193 to 42.78.4.20642.78.4.20714
7842.78.4.208/2842.78.4.209 to 42.78.4.22242.78.4.22314
7942.78.4.224/2842.78.4.225 to 42.78.4.23842.78.4.23914
8042.78.4.240/2842.78.4.241 to 42.78.4.25442.78.4.25514
8142.78.5.0/2842.78.5.1 to 42.78.5.1442.78.5.1514
8242.78.5.16/2842.78.5.17 to 42.78.5.3042.78.5.3114
8342.78.5.32/2842.78.5.33 to 42.78.5.4642.78.5.4714
8442.78.5.48/2842.78.5.49 to 42.78.5.6242.78.5.6314
8542.78.5.64/2842.78.5.65 to 42.78.5.7842.78.5.7914
8642.78.5.80/2842.78.5.81 to 42.78.5.9442.78.5.9514
8742.78.5.96/2842.78.5.97 to 42.78.5.11042.78.5.11114
8842.78.5.112/2842.78.5.113 to 42.78.5.12642.78.5.12714
8942.78.5.128/2842.78.5.129 to 42.78.5.14242.78.5.14314
9042.78.5.144/2842.78.5.145 to 42.78.5.15842.78.5.15914
9142.78.5.160/2842.78.5.161 to 42.78.5.17442.78.5.17514
9242.78.5.176/2842.78.5.177 to 42.78.5.19042.78.5.19114
9342.78.5.192/2842.78.5.193 to 42.78.5.20642.78.5.20714
9442.78.5.208/2842.78.5.209 to 42.78.5.22242.78.5.22314
9542.78.5.224/2842.78.5.225 to 42.78.5.23842.78.5.23914
9642.78.5.240/2842.78.5.241 to 42.78.5.25442.78.5.25514
9742.78.6.0/2842.78.6.1 to 42.78.6.1442.78.6.1514
9842.78.6.16/2842.78.6.17 to 42.78.6.3042.78.6.3114
9942.78.6.32/2842.78.6.33 to 42.78.6.4642.78.6.4714
10042.78.6.48/2842.78.6.49 to 42.78.6.6242.78.6.6314
10142.78.6.64/2842.78.6.65 to 42.78.6.7842.78.6.7914
10242.78.6.80/2842.78.6.81 to 42.78.6.9442.78.6.9514
10342.78.6.96/2842.78.6.97 to 42.78.6.11042.78.6.11114
10442.78.6.112/2842.78.6.113 to 42.78.6.12642.78.6.12714
10542.78.6.128/2842.78.6.129 to 42.78.6.14242.78.6.14314
10642.78.6.144/2842.78.6.145 to 42.78.6.15842.78.6.15914
10742.78.6.160/2842.78.6.161 to 42.78.6.17442.78.6.17514
10842.78.6.176/2842.78.6.177 to 42.78.6.19042.78.6.19114
10942.78.6.192/2842.78.6.193 to 42.78.6.20642.78.6.20714
11042.78.6.208/2842.78.6.209 to 42.78.6.22242.78.6.22314
11142.78.6.224/2842.78.6.225 to 42.78.6.23842.78.6.23914
11242.78.6.240/2842.78.6.241 to 42.78.6.25442.78.6.25514
11342.78.7.0/2842.78.7.1 to 42.78.7.1442.78.7.1514
11442.78.7.16/2842.78.7.17 to 42.78.7.3042.78.7.3114
11542.78.7.32/2842.78.7.33 to 42.78.7.4642.78.7.4714
11642.78.7.48/2842.78.7.49 to 42.78.7.6242.78.7.6314
11742.78.7.64/2842.78.7.65 to 42.78.7.7842.78.7.7914
11842.78.7.80/2842.78.7.81 to 42.78.7.9442.78.7.9514
11942.78.7.96/2842.78.7.97 to 42.78.7.11042.78.7.11114
12042.78.7.112/2842.78.7.113 to 42.78.7.12642.78.7.12714
12142.78.7.128/2842.78.7.129 to 42.78.7.14242.78.7.14314
12242.78.7.144/2842.78.7.145 to 42.78.7.15842.78.7.15914
12342.78.7.160/2842.78.7.161 to 42.78.7.17442.78.7.17514
12442.78.7.176/2842.78.7.177 to 42.78.7.19042.78.7.19114
12542.78.7.192/2842.78.7.193 to 42.78.7.20642.78.7.20714
12642.78.7.208/2842.78.7.209 to 42.78.7.22242.78.7.22314
12742.78.7.224/2842.78.7.225 to 42.78.7.23842.78.7.23914
12842.78.7.240/2842.78.7.241 to 42.78.7.25442.78.7.25514
12942.78.8.0/2842.78.8.1 to 42.78.8.1442.78.8.1514
13042.78.8.16/2842.78.8.17 to 42.78.8.3042.78.8.3114
13142.78.8.32/2842.78.8.33 to 42.78.8.4642.78.8.4714
13242.78.8.48/2842.78.8.49 to 42.78.8.6242.78.8.6314
13342.78.8.64/2842.78.8.65 to 42.78.8.7842.78.8.7914
13442.78.8.80/2842.78.8.81 to 42.78.8.9442.78.8.9514
13542.78.8.96/2842.78.8.97 to 42.78.8.11042.78.8.11114
13642.78.8.112/2842.78.8.113 to 42.78.8.12642.78.8.12714
13742.78.8.128/2842.78.8.129 to 42.78.8.14242.78.8.14314
13842.78.8.144/2842.78.8.145 to 42.78.8.15842.78.8.15914
13942.78.8.160/2842.78.8.161 to 42.78.8.17442.78.8.17514
14042.78.8.176/2842.78.8.177 to 42.78.8.19042.78.8.19114
14142.78.8.192/2842.78.8.193 to 42.78.8.20642.78.8.20714
14242.78.8.208/2842.78.8.209 to 42.78.8.22242.78.8.22314
14342.78.8.224/2842.78.8.225 to 42.78.8.23842.78.8.23914
14442.78.8.240/2842.78.8.241 to 42.78.8.25442.78.8.25514
14542.78.9.0/2842.78.9.1 to 42.78.9.1442.78.9.1514
14642.78.9.16/2842.78.9.17 to 42.78.9.3042.78.9.3114
14742.78.9.32/2842.78.9.33 to 42.78.9.4642.78.9.4714
14842.78.9.48/2842.78.9.49 to 42.78.9.6242.78.9.6314
14942.78.9.64/2842.78.9.65 to 42.78.9.7842.78.9.7914
15042.78.9.80/2842.78.9.81 to 42.78.9.9442.78.9.9514
15142.78.9.96/2842.78.9.97 to 42.78.9.11042.78.9.11114
15242.78.9.112/2842.78.9.113 to 42.78.9.12642.78.9.12714
15342.78.9.128/2842.78.9.129 to 42.78.9.14242.78.9.14314
15442.78.9.144/2842.78.9.145 to 42.78.9.15842.78.9.15914
15542.78.9.160/2842.78.9.161 to 42.78.9.17442.78.9.17514
15642.78.9.176/2842.78.9.177 to 42.78.9.19042.78.9.19114
15742.78.9.192/2842.78.9.193 to 42.78.9.20642.78.9.20714
15842.78.9.208/2842.78.9.209 to 42.78.9.22242.78.9.22314
15942.78.9.224/2842.78.9.225 to 42.78.9.23842.78.9.23914
16042.78.9.240/2842.78.9.241 to 42.78.9.25442.78.9.25514
16142.78.10.0/2842.78.10.1 to 42.78.10.1442.78.10.1514
16242.78.10.16/2842.78.10.17 to 42.78.10.3042.78.10.3114
16342.78.10.32/2842.78.10.33 to 42.78.10.4642.78.10.4714
16442.78.10.48/2842.78.10.49 to 42.78.10.6242.78.10.6314
16542.78.10.64/2842.78.10.65 to 42.78.10.7842.78.10.7914
16642.78.10.80/2842.78.10.81 to 42.78.10.9442.78.10.9514
16742.78.10.96/2842.78.10.97 to 42.78.10.11042.78.10.11114
16842.78.10.112/2842.78.10.113 to 42.78.10.12642.78.10.12714
16942.78.10.128/2842.78.10.129 to 42.78.10.14242.78.10.14314
17042.78.10.144/2842.78.10.145 to 42.78.10.15842.78.10.15914
17142.78.10.160/2842.78.10.161 to 42.78.10.17442.78.10.17514
17242.78.10.176/2842.78.10.177 to 42.78.10.19042.78.10.19114
17342.78.10.192/2842.78.10.193 to 42.78.10.20642.78.10.20714
17442.78.10.208/2842.78.10.209 to 42.78.10.22242.78.10.22314
17542.78.10.224/2842.78.10.225 to 42.78.10.23842.78.10.23914
17642.78.10.240/2842.78.10.241 to 42.78.10.25442.78.10.25514
17742.78.11.0/2842.78.11.1 to 42.78.11.1442.78.11.1514
17842.78.11.16/2842.78.11.17 to 42.78.11.3042.78.11.3114
17942.78.11.32/2842.78.11.33 to 42.78.11.4642.78.11.4714
18042.78.11.48/2842.78.11.49 to 42.78.11.6242.78.11.6314
18142.78.11.64/2842.78.11.65 to 42.78.11.7842.78.11.7914
18242.78.11.80/2842.78.11.81 to 42.78.11.9442.78.11.9514
18342.78.11.96/2842.78.11.97 to 42.78.11.11042.78.11.11114
18442.78.11.112/2842.78.11.113 to 42.78.11.12642.78.11.12714
18542.78.11.128/2842.78.11.129 to 42.78.11.14242.78.11.14314
18642.78.11.144/2842.78.11.145 to 42.78.11.15842.78.11.15914
18742.78.11.160/2842.78.11.161 to 42.78.11.17442.78.11.17514
18842.78.11.176/2842.78.11.177 to 42.78.11.19042.78.11.19114
18942.78.11.192/2842.78.11.193 to 42.78.11.20642.78.11.20714
19042.78.11.208/2842.78.11.209 to 42.78.11.22242.78.11.22314
19142.78.11.224/2842.78.11.225 to 42.78.11.23842.78.11.23914
19242.78.11.240/2842.78.11.241 to 42.78.11.25442.78.11.25514
19342.78.12.0/2842.78.12.1 to 42.78.12.1442.78.12.1514
19442.78.12.16/2842.78.12.17 to 42.78.12.3042.78.12.3114
19542.78.12.32/2842.78.12.33 to 42.78.12.4642.78.12.4714
19642.78.12.48/2842.78.12.49 to 42.78.12.6242.78.12.6314
19742.78.12.64/2842.78.12.65 to 42.78.12.7842.78.12.7914
19842.78.12.80/2842.78.12.81 to 42.78.12.9442.78.12.9514
19942.78.12.96/2842.78.12.97 to 42.78.12.11042.78.12.11114
20042.78.12.112/2842.78.12.113 to 42.78.12.12642.78.12.12714
20142.78.12.128/2842.78.12.129 to 42.78.12.14242.78.12.14314
20242.78.12.144/2842.78.12.145 to 42.78.12.15842.78.12.15914
20342.78.12.160/2842.78.12.161 to 42.78.12.17442.78.12.17514
20442.78.12.176/2842.78.12.177 to 42.78.12.19042.78.12.19114
20542.78.12.192/2842.78.12.193 to 42.78.12.20642.78.12.20714
20642.78.12.208/2842.78.12.209 to 42.78.12.22242.78.12.22314
20742.78.12.224/2842.78.12.225 to 42.78.12.23842.78.12.23914
20842.78.12.240/2842.78.12.241 to 42.78.12.25442.78.12.25514
20942.78.13.0/2842.78.13.1 to 42.78.13.1442.78.13.1514
21042.78.13.16/2842.78.13.17 to 42.78.13.3042.78.13.3114
21142.78.13.32/2842.78.13.33 to 42.78.13.4642.78.13.4714
21242.78.13.48/2842.78.13.49 to 42.78.13.6242.78.13.6314
21342.78.13.64/2842.78.13.65 to 42.78.13.7842.78.13.7914
21442.78.13.80/2842.78.13.81 to 42.78.13.9442.78.13.9514
21542.78.13.96/2842.78.13.97 to 42.78.13.11042.78.13.11114
21642.78.13.112/2842.78.13.113 to 42.78.13.12642.78.13.12714
21742.78.13.128/2842.78.13.129 to 42.78.13.14242.78.13.14314
21842.78.13.144/2842.78.13.145 to 42.78.13.15842.78.13.15914
21942.78.13.160/2842.78.13.161 to 42.78.13.17442.78.13.17514
22042.78.13.176/2842.78.13.177 to 42.78.13.19042.78.13.19114
22142.78.13.192/2842.78.13.193 to 42.78.13.20642.78.13.20714
22242.78.13.208/2842.78.13.209 to 42.78.13.22242.78.13.22314
22342.78.13.224/2842.78.13.225 to 42.78.13.23842.78.13.23914
22442.78.13.240/2842.78.13.241 to 42.78.13.25442.78.13.25514
22542.78.14.0/2842.78.14.1 to 42.78.14.1442.78.14.1514
22642.78.14.16/2842.78.14.17 to 42.78.14.3042.78.14.3114
22742.78.14.32/2842.78.14.33 to 42.78.14.4642.78.14.4714
22842.78.14.48/2842.78.14.49 to 42.78.14.6242.78.14.6314
22942.78.14.64/2842.78.14.65 to 42.78.14.7842.78.14.7914
23042.78.14.80/2842.78.14.81 to 42.78.14.9442.78.14.9514
23142.78.14.96/2842.78.14.97 to 42.78.14.11042.78.14.11114
23242.78.14.112/2842.78.14.113 to 42.78.14.12642.78.14.12714
23342.78.14.128/2842.78.14.129 to 42.78.14.14242.78.14.14314
23442.78.14.144/2842.78.14.145 to 42.78.14.15842.78.14.15914
23542.78.14.160/2842.78.14.161 to 42.78.14.17442.78.14.17514
23642.78.14.176/2842.78.14.177 to 42.78.14.19042.78.14.19114
23742.78.14.192/2842.78.14.193 to 42.78.14.20642.78.14.20714
23842.78.14.208/2842.78.14.209 to 42.78.14.22242.78.14.22314
23942.78.14.224/2842.78.14.225 to 42.78.14.23842.78.14.23914
24042.78.14.240/2842.78.14.241 to 42.78.14.25442.78.14.25514
24142.78.15.0/2842.78.15.1 to 42.78.15.1442.78.15.1514
24242.78.15.16/2842.78.15.17 to 42.78.15.3042.78.15.3114
24342.78.15.32/2842.78.15.33 to 42.78.15.4642.78.15.4714
24442.78.15.48/2842.78.15.49 to 42.78.15.6242.78.15.6314
24542.78.15.64/2842.78.15.65 to 42.78.15.7842.78.15.7914
24642.78.15.80/2842.78.15.81 to 42.78.15.9442.78.15.9514
24742.78.15.96/2842.78.15.97 to 42.78.15.11042.78.15.11114
24842.78.15.112/2842.78.15.113 to 42.78.15.12642.78.15.12714
24942.78.15.128/2842.78.15.129 to 42.78.15.14242.78.15.14314
25042.78.15.144/2842.78.15.145 to 42.78.15.15842.78.15.15914
25142.78.15.160/2842.78.15.161 to 42.78.15.17442.78.15.17514
25242.78.15.176/2842.78.15.177 to 42.78.15.19042.78.15.19114
25342.78.15.192/2842.78.15.193 to 42.78.15.20642.78.15.20714
25442.78.15.208/2842.78.15.209 to 42.78.15.22242.78.15.22314
25542.78.15.224/2842.78.15.225 to 42.78.15.23842.78.15.23914
25642.78.15.240/2842.78.15.241 to 42.78.15.25442.78.15.25514

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.