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.

Network12.3.192.0/19
Usable hosts8,190
Subnet mask255.255.224.0
Addresses8,192
Network address
12.3.192.0
Broadcast address
12.3.223.255
First usable
12.3.192.1
Last usable
12.3.223.254
Usable hosts
8,190 (8,192 less the network and broadcast addresses)
Subnet mask
255.255.224.0
Wildcard mask
0.0.31.255 (Cisco ACLs, OSPF)
Prefix length
/19
Type
Public public
Old class
A (default /8)
As numbers
Hex 0C03C000 · Integer 201572352 to 201580543
Reverse DNS zones
192.3.12.in-addr.arpa
193.3.12.in-addr.arpa
194.3.12.in-addr.arpa
195.3.12.in-addr.arpa
196.3.12.in-addr.arpa
197.3.12.in-addr.arpa
198.3.12.in-addr.arpa
199.3.12.in-addr.arpa
200.3.12.in-addr.arpa
201.3.12.in-addr.arpa
202.3.12.in-addr.arpa
203.3.12.in-addr.arpa
204.3.12.in-addr.arpa
205.3.12.in-addr.arpa
206.3.12.in-addr.arpa
207.3.12.in-addr.arpa
and 16 more
/19 is not on a 8-bit boundary, so it takes 32 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00001100.00000011.11000000.0000000012.3.192.0
Subnet mask11111111.11111111.11100000.00000000255.255.224.0
Network00001100.00000011.11000000.0000000012.3.192.0
Broadcast00001100.00000011.11011111.1111111112.3.223.255
Split into smaller subnets/29
/20 (2)/21 (4)/22 (8)/23 (16)/24 (32)/25 (64)/26 (128)/27 (256)/28 (512)/29 (1,024)/30 (2,048)/31 (4,096)

12.3.192.0/19 makes 1,024 subnets of /29; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
112.3.192.0/2912.3.192.1 to 12.3.192.612.3.192.76
212.3.192.8/2912.3.192.9 to 12.3.192.1412.3.192.156
312.3.192.16/2912.3.192.17 to 12.3.192.2212.3.192.236
412.3.192.24/2912.3.192.25 to 12.3.192.3012.3.192.316
512.3.192.32/2912.3.192.33 to 12.3.192.3812.3.192.396
612.3.192.40/2912.3.192.41 to 12.3.192.4612.3.192.476
712.3.192.48/2912.3.192.49 to 12.3.192.5412.3.192.556
812.3.192.56/2912.3.192.57 to 12.3.192.6212.3.192.636
912.3.192.64/2912.3.192.65 to 12.3.192.7012.3.192.716
1012.3.192.72/2912.3.192.73 to 12.3.192.7812.3.192.796
1112.3.192.80/2912.3.192.81 to 12.3.192.8612.3.192.876
1212.3.192.88/2912.3.192.89 to 12.3.192.9412.3.192.956
1312.3.192.96/2912.3.192.97 to 12.3.192.10212.3.192.1036
1412.3.192.104/2912.3.192.105 to 12.3.192.11012.3.192.1116
1512.3.192.112/2912.3.192.113 to 12.3.192.11812.3.192.1196
1612.3.192.120/2912.3.192.121 to 12.3.192.12612.3.192.1276
1712.3.192.128/2912.3.192.129 to 12.3.192.13412.3.192.1356
1812.3.192.136/2912.3.192.137 to 12.3.192.14212.3.192.1436
1912.3.192.144/2912.3.192.145 to 12.3.192.15012.3.192.1516
2012.3.192.152/2912.3.192.153 to 12.3.192.15812.3.192.1596
2112.3.192.160/2912.3.192.161 to 12.3.192.16612.3.192.1676
2212.3.192.168/2912.3.192.169 to 12.3.192.17412.3.192.1756
2312.3.192.176/2912.3.192.177 to 12.3.192.18212.3.192.1836
2412.3.192.184/2912.3.192.185 to 12.3.192.19012.3.192.1916
2512.3.192.192/2912.3.192.193 to 12.3.192.19812.3.192.1996
2612.3.192.200/2912.3.192.201 to 12.3.192.20612.3.192.2076
2712.3.192.208/2912.3.192.209 to 12.3.192.21412.3.192.2156
2812.3.192.216/2912.3.192.217 to 12.3.192.22212.3.192.2236
2912.3.192.224/2912.3.192.225 to 12.3.192.23012.3.192.2316
3012.3.192.232/2912.3.192.233 to 12.3.192.23812.3.192.2396
3112.3.192.240/2912.3.192.241 to 12.3.192.24612.3.192.2476
3212.3.192.248/2912.3.192.249 to 12.3.192.25412.3.192.2556
3312.3.193.0/2912.3.193.1 to 12.3.193.612.3.193.76
3412.3.193.8/2912.3.193.9 to 12.3.193.1412.3.193.156
3512.3.193.16/2912.3.193.17 to 12.3.193.2212.3.193.236
3612.3.193.24/2912.3.193.25 to 12.3.193.3012.3.193.316
3712.3.193.32/2912.3.193.33 to 12.3.193.3812.3.193.396
3812.3.193.40/2912.3.193.41 to 12.3.193.4612.3.193.476
3912.3.193.48/2912.3.193.49 to 12.3.193.5412.3.193.556
4012.3.193.56/2912.3.193.57 to 12.3.193.6212.3.193.636
4112.3.193.64/2912.3.193.65 to 12.3.193.7012.3.193.716
4212.3.193.72/2912.3.193.73 to 12.3.193.7812.3.193.796
4312.3.193.80/2912.3.193.81 to 12.3.193.8612.3.193.876
4412.3.193.88/2912.3.193.89 to 12.3.193.9412.3.193.956
4512.3.193.96/2912.3.193.97 to 12.3.193.10212.3.193.1036
4612.3.193.104/2912.3.193.105 to 12.3.193.11012.3.193.1116
4712.3.193.112/2912.3.193.113 to 12.3.193.11812.3.193.1196
4812.3.193.120/2912.3.193.121 to 12.3.193.12612.3.193.1276
4912.3.193.128/2912.3.193.129 to 12.3.193.13412.3.193.1356
5012.3.193.136/2912.3.193.137 to 12.3.193.14212.3.193.1436
5112.3.193.144/2912.3.193.145 to 12.3.193.15012.3.193.1516
5212.3.193.152/2912.3.193.153 to 12.3.193.15812.3.193.1596
5312.3.193.160/2912.3.193.161 to 12.3.193.16612.3.193.1676
5412.3.193.168/2912.3.193.169 to 12.3.193.17412.3.193.1756
5512.3.193.176/2912.3.193.177 to 12.3.193.18212.3.193.1836
5612.3.193.184/2912.3.193.185 to 12.3.193.19012.3.193.1916
5712.3.193.192/2912.3.193.193 to 12.3.193.19812.3.193.1996
5812.3.193.200/2912.3.193.201 to 12.3.193.20612.3.193.2076
5912.3.193.208/2912.3.193.209 to 12.3.193.21412.3.193.2156
6012.3.193.216/2912.3.193.217 to 12.3.193.22212.3.193.2236
6112.3.193.224/2912.3.193.225 to 12.3.193.23012.3.193.2316
6212.3.193.232/2912.3.193.233 to 12.3.193.23812.3.193.2396
6312.3.193.240/2912.3.193.241 to 12.3.193.24612.3.193.2476
6412.3.193.248/2912.3.193.249 to 12.3.193.25412.3.193.2556
6512.3.194.0/2912.3.194.1 to 12.3.194.612.3.194.76
6612.3.194.8/2912.3.194.9 to 12.3.194.1412.3.194.156
6712.3.194.16/2912.3.194.17 to 12.3.194.2212.3.194.236
6812.3.194.24/2912.3.194.25 to 12.3.194.3012.3.194.316
6912.3.194.32/2912.3.194.33 to 12.3.194.3812.3.194.396
7012.3.194.40/2912.3.194.41 to 12.3.194.4612.3.194.476
7112.3.194.48/2912.3.194.49 to 12.3.194.5412.3.194.556
7212.3.194.56/2912.3.194.57 to 12.3.194.6212.3.194.636
7312.3.194.64/2912.3.194.65 to 12.3.194.7012.3.194.716
7412.3.194.72/2912.3.194.73 to 12.3.194.7812.3.194.796
7512.3.194.80/2912.3.194.81 to 12.3.194.8612.3.194.876
7612.3.194.88/2912.3.194.89 to 12.3.194.9412.3.194.956
7712.3.194.96/2912.3.194.97 to 12.3.194.10212.3.194.1036
7812.3.194.104/2912.3.194.105 to 12.3.194.11012.3.194.1116
7912.3.194.112/2912.3.194.113 to 12.3.194.11812.3.194.1196
8012.3.194.120/2912.3.194.121 to 12.3.194.12612.3.194.1276
8112.3.194.128/2912.3.194.129 to 12.3.194.13412.3.194.1356
8212.3.194.136/2912.3.194.137 to 12.3.194.14212.3.194.1436
8312.3.194.144/2912.3.194.145 to 12.3.194.15012.3.194.1516
8412.3.194.152/2912.3.194.153 to 12.3.194.15812.3.194.1596
8512.3.194.160/2912.3.194.161 to 12.3.194.16612.3.194.1676
8612.3.194.168/2912.3.194.169 to 12.3.194.17412.3.194.1756
8712.3.194.176/2912.3.194.177 to 12.3.194.18212.3.194.1836
8812.3.194.184/2912.3.194.185 to 12.3.194.19012.3.194.1916
8912.3.194.192/2912.3.194.193 to 12.3.194.19812.3.194.1996
9012.3.194.200/2912.3.194.201 to 12.3.194.20612.3.194.2076
9112.3.194.208/2912.3.194.209 to 12.3.194.21412.3.194.2156
9212.3.194.216/2912.3.194.217 to 12.3.194.22212.3.194.2236
9312.3.194.224/2912.3.194.225 to 12.3.194.23012.3.194.2316
9412.3.194.232/2912.3.194.233 to 12.3.194.23812.3.194.2396
9512.3.194.240/2912.3.194.241 to 12.3.194.24612.3.194.2476
9612.3.194.248/2912.3.194.249 to 12.3.194.25412.3.194.2556
9712.3.195.0/2912.3.195.1 to 12.3.195.612.3.195.76
9812.3.195.8/2912.3.195.9 to 12.3.195.1412.3.195.156
9912.3.195.16/2912.3.195.17 to 12.3.195.2212.3.195.236
10012.3.195.24/2912.3.195.25 to 12.3.195.3012.3.195.316
10112.3.195.32/2912.3.195.33 to 12.3.195.3812.3.195.396
10212.3.195.40/2912.3.195.41 to 12.3.195.4612.3.195.476
10312.3.195.48/2912.3.195.49 to 12.3.195.5412.3.195.556
10412.3.195.56/2912.3.195.57 to 12.3.195.6212.3.195.636
10512.3.195.64/2912.3.195.65 to 12.3.195.7012.3.195.716
10612.3.195.72/2912.3.195.73 to 12.3.195.7812.3.195.796
10712.3.195.80/2912.3.195.81 to 12.3.195.8612.3.195.876
10812.3.195.88/2912.3.195.89 to 12.3.195.9412.3.195.956
10912.3.195.96/2912.3.195.97 to 12.3.195.10212.3.195.1036
11012.3.195.104/2912.3.195.105 to 12.3.195.11012.3.195.1116
11112.3.195.112/2912.3.195.113 to 12.3.195.11812.3.195.1196
11212.3.195.120/2912.3.195.121 to 12.3.195.12612.3.195.1276
11312.3.195.128/2912.3.195.129 to 12.3.195.13412.3.195.1356
11412.3.195.136/2912.3.195.137 to 12.3.195.14212.3.195.1436
11512.3.195.144/2912.3.195.145 to 12.3.195.15012.3.195.1516
11612.3.195.152/2912.3.195.153 to 12.3.195.15812.3.195.1596
11712.3.195.160/2912.3.195.161 to 12.3.195.16612.3.195.1676
11812.3.195.168/2912.3.195.169 to 12.3.195.17412.3.195.1756
11912.3.195.176/2912.3.195.177 to 12.3.195.18212.3.195.1836
12012.3.195.184/2912.3.195.185 to 12.3.195.19012.3.195.1916
12112.3.195.192/2912.3.195.193 to 12.3.195.19812.3.195.1996
12212.3.195.200/2912.3.195.201 to 12.3.195.20612.3.195.2076
12312.3.195.208/2912.3.195.209 to 12.3.195.21412.3.195.2156
12412.3.195.216/2912.3.195.217 to 12.3.195.22212.3.195.2236
12512.3.195.224/2912.3.195.225 to 12.3.195.23012.3.195.2316
12612.3.195.232/2912.3.195.233 to 12.3.195.23812.3.195.2396
12712.3.195.240/2912.3.195.241 to 12.3.195.24612.3.195.2476
12812.3.195.248/2912.3.195.249 to 12.3.195.25412.3.195.2556
12912.3.196.0/2912.3.196.1 to 12.3.196.612.3.196.76
13012.3.196.8/2912.3.196.9 to 12.3.196.1412.3.196.156
13112.3.196.16/2912.3.196.17 to 12.3.196.2212.3.196.236
13212.3.196.24/2912.3.196.25 to 12.3.196.3012.3.196.316
13312.3.196.32/2912.3.196.33 to 12.3.196.3812.3.196.396
13412.3.196.40/2912.3.196.41 to 12.3.196.4612.3.196.476
13512.3.196.48/2912.3.196.49 to 12.3.196.5412.3.196.556
13612.3.196.56/2912.3.196.57 to 12.3.196.6212.3.196.636
13712.3.196.64/2912.3.196.65 to 12.3.196.7012.3.196.716
13812.3.196.72/2912.3.196.73 to 12.3.196.7812.3.196.796
13912.3.196.80/2912.3.196.81 to 12.3.196.8612.3.196.876
14012.3.196.88/2912.3.196.89 to 12.3.196.9412.3.196.956
14112.3.196.96/2912.3.196.97 to 12.3.196.10212.3.196.1036
14212.3.196.104/2912.3.196.105 to 12.3.196.11012.3.196.1116
14312.3.196.112/2912.3.196.113 to 12.3.196.11812.3.196.1196
14412.3.196.120/2912.3.196.121 to 12.3.196.12612.3.196.1276
14512.3.196.128/2912.3.196.129 to 12.3.196.13412.3.196.1356
14612.3.196.136/2912.3.196.137 to 12.3.196.14212.3.196.1436
14712.3.196.144/2912.3.196.145 to 12.3.196.15012.3.196.1516
14812.3.196.152/2912.3.196.153 to 12.3.196.15812.3.196.1596
14912.3.196.160/2912.3.196.161 to 12.3.196.16612.3.196.1676
15012.3.196.168/2912.3.196.169 to 12.3.196.17412.3.196.1756
15112.3.196.176/2912.3.196.177 to 12.3.196.18212.3.196.1836
15212.3.196.184/2912.3.196.185 to 12.3.196.19012.3.196.1916
15312.3.196.192/2912.3.196.193 to 12.3.196.19812.3.196.1996
15412.3.196.200/2912.3.196.201 to 12.3.196.20612.3.196.2076
15512.3.196.208/2912.3.196.209 to 12.3.196.21412.3.196.2156
15612.3.196.216/2912.3.196.217 to 12.3.196.22212.3.196.2236
15712.3.196.224/2912.3.196.225 to 12.3.196.23012.3.196.2316
15812.3.196.232/2912.3.196.233 to 12.3.196.23812.3.196.2396
15912.3.196.240/2912.3.196.241 to 12.3.196.24612.3.196.2476
16012.3.196.248/2912.3.196.249 to 12.3.196.25412.3.196.2556
16112.3.197.0/2912.3.197.1 to 12.3.197.612.3.197.76
16212.3.197.8/2912.3.197.9 to 12.3.197.1412.3.197.156
16312.3.197.16/2912.3.197.17 to 12.3.197.2212.3.197.236
16412.3.197.24/2912.3.197.25 to 12.3.197.3012.3.197.316
16512.3.197.32/2912.3.197.33 to 12.3.197.3812.3.197.396
16612.3.197.40/2912.3.197.41 to 12.3.197.4612.3.197.476
16712.3.197.48/2912.3.197.49 to 12.3.197.5412.3.197.556
16812.3.197.56/2912.3.197.57 to 12.3.197.6212.3.197.636
16912.3.197.64/2912.3.197.65 to 12.3.197.7012.3.197.716
17012.3.197.72/2912.3.197.73 to 12.3.197.7812.3.197.796
17112.3.197.80/2912.3.197.81 to 12.3.197.8612.3.197.876
17212.3.197.88/2912.3.197.89 to 12.3.197.9412.3.197.956
17312.3.197.96/2912.3.197.97 to 12.3.197.10212.3.197.1036
17412.3.197.104/2912.3.197.105 to 12.3.197.11012.3.197.1116
17512.3.197.112/2912.3.197.113 to 12.3.197.11812.3.197.1196
17612.3.197.120/2912.3.197.121 to 12.3.197.12612.3.197.1276
17712.3.197.128/2912.3.197.129 to 12.3.197.13412.3.197.1356
17812.3.197.136/2912.3.197.137 to 12.3.197.14212.3.197.1436
17912.3.197.144/2912.3.197.145 to 12.3.197.15012.3.197.1516
18012.3.197.152/2912.3.197.153 to 12.3.197.15812.3.197.1596
18112.3.197.160/2912.3.197.161 to 12.3.197.16612.3.197.1676
18212.3.197.168/2912.3.197.169 to 12.3.197.17412.3.197.1756
18312.3.197.176/2912.3.197.177 to 12.3.197.18212.3.197.1836
18412.3.197.184/2912.3.197.185 to 12.3.197.19012.3.197.1916
18512.3.197.192/2912.3.197.193 to 12.3.197.19812.3.197.1996
18612.3.197.200/2912.3.197.201 to 12.3.197.20612.3.197.2076
18712.3.197.208/2912.3.197.209 to 12.3.197.21412.3.197.2156
18812.3.197.216/2912.3.197.217 to 12.3.197.22212.3.197.2236
18912.3.197.224/2912.3.197.225 to 12.3.197.23012.3.197.2316
19012.3.197.232/2912.3.197.233 to 12.3.197.23812.3.197.2396
19112.3.197.240/2912.3.197.241 to 12.3.197.24612.3.197.2476
19212.3.197.248/2912.3.197.249 to 12.3.197.25412.3.197.2556
19312.3.198.0/2912.3.198.1 to 12.3.198.612.3.198.76
19412.3.198.8/2912.3.198.9 to 12.3.198.1412.3.198.156
19512.3.198.16/2912.3.198.17 to 12.3.198.2212.3.198.236
19612.3.198.24/2912.3.198.25 to 12.3.198.3012.3.198.316
19712.3.198.32/2912.3.198.33 to 12.3.198.3812.3.198.396
19812.3.198.40/2912.3.198.41 to 12.3.198.4612.3.198.476
19912.3.198.48/2912.3.198.49 to 12.3.198.5412.3.198.556
20012.3.198.56/2912.3.198.57 to 12.3.198.6212.3.198.636
20112.3.198.64/2912.3.198.65 to 12.3.198.7012.3.198.716
20212.3.198.72/2912.3.198.73 to 12.3.198.7812.3.198.796
20312.3.198.80/2912.3.198.81 to 12.3.198.8612.3.198.876
20412.3.198.88/2912.3.198.89 to 12.3.198.9412.3.198.956
20512.3.198.96/2912.3.198.97 to 12.3.198.10212.3.198.1036
20612.3.198.104/2912.3.198.105 to 12.3.198.11012.3.198.1116
20712.3.198.112/2912.3.198.113 to 12.3.198.11812.3.198.1196
20812.3.198.120/2912.3.198.121 to 12.3.198.12612.3.198.1276
20912.3.198.128/2912.3.198.129 to 12.3.198.13412.3.198.1356
21012.3.198.136/2912.3.198.137 to 12.3.198.14212.3.198.1436
21112.3.198.144/2912.3.198.145 to 12.3.198.15012.3.198.1516
21212.3.198.152/2912.3.198.153 to 12.3.198.15812.3.198.1596
21312.3.198.160/2912.3.198.161 to 12.3.198.16612.3.198.1676
21412.3.198.168/2912.3.198.169 to 12.3.198.17412.3.198.1756
21512.3.198.176/2912.3.198.177 to 12.3.198.18212.3.198.1836
21612.3.198.184/2912.3.198.185 to 12.3.198.19012.3.198.1916
21712.3.198.192/2912.3.198.193 to 12.3.198.19812.3.198.1996
21812.3.198.200/2912.3.198.201 to 12.3.198.20612.3.198.2076
21912.3.198.208/2912.3.198.209 to 12.3.198.21412.3.198.2156
22012.3.198.216/2912.3.198.217 to 12.3.198.22212.3.198.2236
22112.3.198.224/2912.3.198.225 to 12.3.198.23012.3.198.2316
22212.3.198.232/2912.3.198.233 to 12.3.198.23812.3.198.2396
22312.3.198.240/2912.3.198.241 to 12.3.198.24612.3.198.2476
22412.3.198.248/2912.3.198.249 to 12.3.198.25412.3.198.2556
22512.3.199.0/2912.3.199.1 to 12.3.199.612.3.199.76
22612.3.199.8/2912.3.199.9 to 12.3.199.1412.3.199.156
22712.3.199.16/2912.3.199.17 to 12.3.199.2212.3.199.236
22812.3.199.24/2912.3.199.25 to 12.3.199.3012.3.199.316
22912.3.199.32/2912.3.199.33 to 12.3.199.3812.3.199.396
23012.3.199.40/2912.3.199.41 to 12.3.199.4612.3.199.476
23112.3.199.48/2912.3.199.49 to 12.3.199.5412.3.199.556
23212.3.199.56/2912.3.199.57 to 12.3.199.6212.3.199.636
23312.3.199.64/2912.3.199.65 to 12.3.199.7012.3.199.716
23412.3.199.72/2912.3.199.73 to 12.3.199.7812.3.199.796
23512.3.199.80/2912.3.199.81 to 12.3.199.8612.3.199.876
23612.3.199.88/2912.3.199.89 to 12.3.199.9412.3.199.956
23712.3.199.96/2912.3.199.97 to 12.3.199.10212.3.199.1036
23812.3.199.104/2912.3.199.105 to 12.3.199.11012.3.199.1116
23912.3.199.112/2912.3.199.113 to 12.3.199.11812.3.199.1196
24012.3.199.120/2912.3.199.121 to 12.3.199.12612.3.199.1276
24112.3.199.128/2912.3.199.129 to 12.3.199.13412.3.199.1356
24212.3.199.136/2912.3.199.137 to 12.3.199.14212.3.199.1436
24312.3.199.144/2912.3.199.145 to 12.3.199.15012.3.199.1516
24412.3.199.152/2912.3.199.153 to 12.3.199.15812.3.199.1596
24512.3.199.160/2912.3.199.161 to 12.3.199.16612.3.199.1676
24612.3.199.168/2912.3.199.169 to 12.3.199.17412.3.199.1756
24712.3.199.176/2912.3.199.177 to 12.3.199.18212.3.199.1836
24812.3.199.184/2912.3.199.185 to 12.3.199.19012.3.199.1916
24912.3.199.192/2912.3.199.193 to 12.3.199.19812.3.199.1996
25012.3.199.200/2912.3.199.201 to 12.3.199.20612.3.199.2076
25112.3.199.208/2912.3.199.209 to 12.3.199.21412.3.199.2156
25212.3.199.216/2912.3.199.217 to 12.3.199.22212.3.199.2236
25312.3.199.224/2912.3.199.225 to 12.3.199.23012.3.199.2316
25412.3.199.232/2912.3.199.233 to 12.3.199.23812.3.199.2396
25512.3.199.240/2912.3.199.241 to 12.3.199.24612.3.199.2476
25612.3.199.248/2912.3.199.249 to 12.3.199.25412.3.199.2556

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.