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.

Network16.3.64.0/19
Usable hosts8,190
Subnet mask255.255.224.0
Addresses8,192
Network address
16.3.64.0
Broadcast address
16.3.95.255
First usable
16.3.64.1
Last usable
16.3.95.254
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 10034000 · Integer 268648448 to 268656639
Reverse DNS zones
64.3.16.in-addr.arpa
65.3.16.in-addr.arpa
66.3.16.in-addr.arpa
67.3.16.in-addr.arpa
68.3.16.in-addr.arpa
69.3.16.in-addr.arpa
70.3.16.in-addr.arpa
71.3.16.in-addr.arpa
72.3.16.in-addr.arpa
73.3.16.in-addr.arpa
74.3.16.in-addr.arpa
75.3.16.in-addr.arpa
76.3.16.in-addr.arpa
77.3.16.in-addr.arpa
78.3.16.in-addr.arpa
79.3.16.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
Address00010000.00000011.01000000.0000000016.3.64.0
Subnet mask11111111.11111111.11100000.00000000255.255.224.0
Network00010000.00000011.01000000.0000000016.3.64.0
Broadcast00010000.00000011.01011111.1111111116.3.95.255
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)

16.3.64.0/19 makes 1,024 subnets of /29; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
116.3.64.0/2916.3.64.1 to 16.3.64.616.3.64.76
216.3.64.8/2916.3.64.9 to 16.3.64.1416.3.64.156
316.3.64.16/2916.3.64.17 to 16.3.64.2216.3.64.236
416.3.64.24/2916.3.64.25 to 16.3.64.3016.3.64.316
516.3.64.32/2916.3.64.33 to 16.3.64.3816.3.64.396
616.3.64.40/2916.3.64.41 to 16.3.64.4616.3.64.476
716.3.64.48/2916.3.64.49 to 16.3.64.5416.3.64.556
816.3.64.56/2916.3.64.57 to 16.3.64.6216.3.64.636
916.3.64.64/2916.3.64.65 to 16.3.64.7016.3.64.716
1016.3.64.72/2916.3.64.73 to 16.3.64.7816.3.64.796
1116.3.64.80/2916.3.64.81 to 16.3.64.8616.3.64.876
1216.3.64.88/2916.3.64.89 to 16.3.64.9416.3.64.956
1316.3.64.96/2916.3.64.97 to 16.3.64.10216.3.64.1036
1416.3.64.104/2916.3.64.105 to 16.3.64.11016.3.64.1116
1516.3.64.112/2916.3.64.113 to 16.3.64.11816.3.64.1196
1616.3.64.120/2916.3.64.121 to 16.3.64.12616.3.64.1276
1716.3.64.128/2916.3.64.129 to 16.3.64.13416.3.64.1356
1816.3.64.136/2916.3.64.137 to 16.3.64.14216.3.64.1436
1916.3.64.144/2916.3.64.145 to 16.3.64.15016.3.64.1516
2016.3.64.152/2916.3.64.153 to 16.3.64.15816.3.64.1596
2116.3.64.160/2916.3.64.161 to 16.3.64.16616.3.64.1676
2216.3.64.168/2916.3.64.169 to 16.3.64.17416.3.64.1756
2316.3.64.176/2916.3.64.177 to 16.3.64.18216.3.64.1836
2416.3.64.184/2916.3.64.185 to 16.3.64.19016.3.64.1916
2516.3.64.192/2916.3.64.193 to 16.3.64.19816.3.64.1996
2616.3.64.200/2916.3.64.201 to 16.3.64.20616.3.64.2076
2716.3.64.208/2916.3.64.209 to 16.3.64.21416.3.64.2156
2816.3.64.216/2916.3.64.217 to 16.3.64.22216.3.64.2236
2916.3.64.224/2916.3.64.225 to 16.3.64.23016.3.64.2316
3016.3.64.232/2916.3.64.233 to 16.3.64.23816.3.64.2396
3116.3.64.240/2916.3.64.241 to 16.3.64.24616.3.64.2476
3216.3.64.248/2916.3.64.249 to 16.3.64.25416.3.64.2556
3316.3.65.0/2916.3.65.1 to 16.3.65.616.3.65.76
3416.3.65.8/2916.3.65.9 to 16.3.65.1416.3.65.156
3516.3.65.16/2916.3.65.17 to 16.3.65.2216.3.65.236
3616.3.65.24/2916.3.65.25 to 16.3.65.3016.3.65.316
3716.3.65.32/2916.3.65.33 to 16.3.65.3816.3.65.396
3816.3.65.40/2916.3.65.41 to 16.3.65.4616.3.65.476
3916.3.65.48/2916.3.65.49 to 16.3.65.5416.3.65.556
4016.3.65.56/2916.3.65.57 to 16.3.65.6216.3.65.636
4116.3.65.64/2916.3.65.65 to 16.3.65.7016.3.65.716
4216.3.65.72/2916.3.65.73 to 16.3.65.7816.3.65.796
4316.3.65.80/2916.3.65.81 to 16.3.65.8616.3.65.876
4416.3.65.88/2916.3.65.89 to 16.3.65.9416.3.65.956
4516.3.65.96/2916.3.65.97 to 16.3.65.10216.3.65.1036
4616.3.65.104/2916.3.65.105 to 16.3.65.11016.3.65.1116
4716.3.65.112/2916.3.65.113 to 16.3.65.11816.3.65.1196
4816.3.65.120/2916.3.65.121 to 16.3.65.12616.3.65.1276
4916.3.65.128/2916.3.65.129 to 16.3.65.13416.3.65.1356
5016.3.65.136/2916.3.65.137 to 16.3.65.14216.3.65.1436
5116.3.65.144/2916.3.65.145 to 16.3.65.15016.3.65.1516
5216.3.65.152/2916.3.65.153 to 16.3.65.15816.3.65.1596
5316.3.65.160/2916.3.65.161 to 16.3.65.16616.3.65.1676
5416.3.65.168/2916.3.65.169 to 16.3.65.17416.3.65.1756
5516.3.65.176/2916.3.65.177 to 16.3.65.18216.3.65.1836
5616.3.65.184/2916.3.65.185 to 16.3.65.19016.3.65.1916
5716.3.65.192/2916.3.65.193 to 16.3.65.19816.3.65.1996
5816.3.65.200/2916.3.65.201 to 16.3.65.20616.3.65.2076
5916.3.65.208/2916.3.65.209 to 16.3.65.21416.3.65.2156
6016.3.65.216/2916.3.65.217 to 16.3.65.22216.3.65.2236
6116.3.65.224/2916.3.65.225 to 16.3.65.23016.3.65.2316
6216.3.65.232/2916.3.65.233 to 16.3.65.23816.3.65.2396
6316.3.65.240/2916.3.65.241 to 16.3.65.24616.3.65.2476
6416.3.65.248/2916.3.65.249 to 16.3.65.25416.3.65.2556
6516.3.66.0/2916.3.66.1 to 16.3.66.616.3.66.76
6616.3.66.8/2916.3.66.9 to 16.3.66.1416.3.66.156
6716.3.66.16/2916.3.66.17 to 16.3.66.2216.3.66.236
6816.3.66.24/2916.3.66.25 to 16.3.66.3016.3.66.316
6916.3.66.32/2916.3.66.33 to 16.3.66.3816.3.66.396
7016.3.66.40/2916.3.66.41 to 16.3.66.4616.3.66.476
7116.3.66.48/2916.3.66.49 to 16.3.66.5416.3.66.556
7216.3.66.56/2916.3.66.57 to 16.3.66.6216.3.66.636
7316.3.66.64/2916.3.66.65 to 16.3.66.7016.3.66.716
7416.3.66.72/2916.3.66.73 to 16.3.66.7816.3.66.796
7516.3.66.80/2916.3.66.81 to 16.3.66.8616.3.66.876
7616.3.66.88/2916.3.66.89 to 16.3.66.9416.3.66.956
7716.3.66.96/2916.3.66.97 to 16.3.66.10216.3.66.1036
7816.3.66.104/2916.3.66.105 to 16.3.66.11016.3.66.1116
7916.3.66.112/2916.3.66.113 to 16.3.66.11816.3.66.1196
8016.3.66.120/2916.3.66.121 to 16.3.66.12616.3.66.1276
8116.3.66.128/2916.3.66.129 to 16.3.66.13416.3.66.1356
8216.3.66.136/2916.3.66.137 to 16.3.66.14216.3.66.1436
8316.3.66.144/2916.3.66.145 to 16.3.66.15016.3.66.1516
8416.3.66.152/2916.3.66.153 to 16.3.66.15816.3.66.1596
8516.3.66.160/2916.3.66.161 to 16.3.66.16616.3.66.1676
8616.3.66.168/2916.3.66.169 to 16.3.66.17416.3.66.1756
8716.3.66.176/2916.3.66.177 to 16.3.66.18216.3.66.1836
8816.3.66.184/2916.3.66.185 to 16.3.66.19016.3.66.1916
8916.3.66.192/2916.3.66.193 to 16.3.66.19816.3.66.1996
9016.3.66.200/2916.3.66.201 to 16.3.66.20616.3.66.2076
9116.3.66.208/2916.3.66.209 to 16.3.66.21416.3.66.2156
9216.3.66.216/2916.3.66.217 to 16.3.66.22216.3.66.2236
9316.3.66.224/2916.3.66.225 to 16.3.66.23016.3.66.2316
9416.3.66.232/2916.3.66.233 to 16.3.66.23816.3.66.2396
9516.3.66.240/2916.3.66.241 to 16.3.66.24616.3.66.2476
9616.3.66.248/2916.3.66.249 to 16.3.66.25416.3.66.2556
9716.3.67.0/2916.3.67.1 to 16.3.67.616.3.67.76
9816.3.67.8/2916.3.67.9 to 16.3.67.1416.3.67.156
9916.3.67.16/2916.3.67.17 to 16.3.67.2216.3.67.236
10016.3.67.24/2916.3.67.25 to 16.3.67.3016.3.67.316
10116.3.67.32/2916.3.67.33 to 16.3.67.3816.3.67.396
10216.3.67.40/2916.3.67.41 to 16.3.67.4616.3.67.476
10316.3.67.48/2916.3.67.49 to 16.3.67.5416.3.67.556
10416.3.67.56/2916.3.67.57 to 16.3.67.6216.3.67.636
10516.3.67.64/2916.3.67.65 to 16.3.67.7016.3.67.716
10616.3.67.72/2916.3.67.73 to 16.3.67.7816.3.67.796
10716.3.67.80/2916.3.67.81 to 16.3.67.8616.3.67.876
10816.3.67.88/2916.3.67.89 to 16.3.67.9416.3.67.956
10916.3.67.96/2916.3.67.97 to 16.3.67.10216.3.67.1036
11016.3.67.104/2916.3.67.105 to 16.3.67.11016.3.67.1116
11116.3.67.112/2916.3.67.113 to 16.3.67.11816.3.67.1196
11216.3.67.120/2916.3.67.121 to 16.3.67.12616.3.67.1276
11316.3.67.128/2916.3.67.129 to 16.3.67.13416.3.67.1356
11416.3.67.136/2916.3.67.137 to 16.3.67.14216.3.67.1436
11516.3.67.144/2916.3.67.145 to 16.3.67.15016.3.67.1516
11616.3.67.152/2916.3.67.153 to 16.3.67.15816.3.67.1596
11716.3.67.160/2916.3.67.161 to 16.3.67.16616.3.67.1676
11816.3.67.168/2916.3.67.169 to 16.3.67.17416.3.67.1756
11916.3.67.176/2916.3.67.177 to 16.3.67.18216.3.67.1836
12016.3.67.184/2916.3.67.185 to 16.3.67.19016.3.67.1916
12116.3.67.192/2916.3.67.193 to 16.3.67.19816.3.67.1996
12216.3.67.200/2916.3.67.201 to 16.3.67.20616.3.67.2076
12316.3.67.208/2916.3.67.209 to 16.3.67.21416.3.67.2156
12416.3.67.216/2916.3.67.217 to 16.3.67.22216.3.67.2236
12516.3.67.224/2916.3.67.225 to 16.3.67.23016.3.67.2316
12616.3.67.232/2916.3.67.233 to 16.3.67.23816.3.67.2396
12716.3.67.240/2916.3.67.241 to 16.3.67.24616.3.67.2476
12816.3.67.248/2916.3.67.249 to 16.3.67.25416.3.67.2556
12916.3.68.0/2916.3.68.1 to 16.3.68.616.3.68.76
13016.3.68.8/2916.3.68.9 to 16.3.68.1416.3.68.156
13116.3.68.16/2916.3.68.17 to 16.3.68.2216.3.68.236
13216.3.68.24/2916.3.68.25 to 16.3.68.3016.3.68.316
13316.3.68.32/2916.3.68.33 to 16.3.68.3816.3.68.396
13416.3.68.40/2916.3.68.41 to 16.3.68.4616.3.68.476
13516.3.68.48/2916.3.68.49 to 16.3.68.5416.3.68.556
13616.3.68.56/2916.3.68.57 to 16.3.68.6216.3.68.636
13716.3.68.64/2916.3.68.65 to 16.3.68.7016.3.68.716
13816.3.68.72/2916.3.68.73 to 16.3.68.7816.3.68.796
13916.3.68.80/2916.3.68.81 to 16.3.68.8616.3.68.876
14016.3.68.88/2916.3.68.89 to 16.3.68.9416.3.68.956
14116.3.68.96/2916.3.68.97 to 16.3.68.10216.3.68.1036
14216.3.68.104/2916.3.68.105 to 16.3.68.11016.3.68.1116
14316.3.68.112/2916.3.68.113 to 16.3.68.11816.3.68.1196
14416.3.68.120/2916.3.68.121 to 16.3.68.12616.3.68.1276
14516.3.68.128/2916.3.68.129 to 16.3.68.13416.3.68.1356
14616.3.68.136/2916.3.68.137 to 16.3.68.14216.3.68.1436
14716.3.68.144/2916.3.68.145 to 16.3.68.15016.3.68.1516
14816.3.68.152/2916.3.68.153 to 16.3.68.15816.3.68.1596
14916.3.68.160/2916.3.68.161 to 16.3.68.16616.3.68.1676
15016.3.68.168/2916.3.68.169 to 16.3.68.17416.3.68.1756
15116.3.68.176/2916.3.68.177 to 16.3.68.18216.3.68.1836
15216.3.68.184/2916.3.68.185 to 16.3.68.19016.3.68.1916
15316.3.68.192/2916.3.68.193 to 16.3.68.19816.3.68.1996
15416.3.68.200/2916.3.68.201 to 16.3.68.20616.3.68.2076
15516.3.68.208/2916.3.68.209 to 16.3.68.21416.3.68.2156
15616.3.68.216/2916.3.68.217 to 16.3.68.22216.3.68.2236
15716.3.68.224/2916.3.68.225 to 16.3.68.23016.3.68.2316
15816.3.68.232/2916.3.68.233 to 16.3.68.23816.3.68.2396
15916.3.68.240/2916.3.68.241 to 16.3.68.24616.3.68.2476
16016.3.68.248/2916.3.68.249 to 16.3.68.25416.3.68.2556
16116.3.69.0/2916.3.69.1 to 16.3.69.616.3.69.76
16216.3.69.8/2916.3.69.9 to 16.3.69.1416.3.69.156
16316.3.69.16/2916.3.69.17 to 16.3.69.2216.3.69.236
16416.3.69.24/2916.3.69.25 to 16.3.69.3016.3.69.316
16516.3.69.32/2916.3.69.33 to 16.3.69.3816.3.69.396
16616.3.69.40/2916.3.69.41 to 16.3.69.4616.3.69.476
16716.3.69.48/2916.3.69.49 to 16.3.69.5416.3.69.556
16816.3.69.56/2916.3.69.57 to 16.3.69.6216.3.69.636
16916.3.69.64/2916.3.69.65 to 16.3.69.7016.3.69.716
17016.3.69.72/2916.3.69.73 to 16.3.69.7816.3.69.796
17116.3.69.80/2916.3.69.81 to 16.3.69.8616.3.69.876
17216.3.69.88/2916.3.69.89 to 16.3.69.9416.3.69.956
17316.3.69.96/2916.3.69.97 to 16.3.69.10216.3.69.1036
17416.3.69.104/2916.3.69.105 to 16.3.69.11016.3.69.1116
17516.3.69.112/2916.3.69.113 to 16.3.69.11816.3.69.1196
17616.3.69.120/2916.3.69.121 to 16.3.69.12616.3.69.1276
17716.3.69.128/2916.3.69.129 to 16.3.69.13416.3.69.1356
17816.3.69.136/2916.3.69.137 to 16.3.69.14216.3.69.1436
17916.3.69.144/2916.3.69.145 to 16.3.69.15016.3.69.1516
18016.3.69.152/2916.3.69.153 to 16.3.69.15816.3.69.1596
18116.3.69.160/2916.3.69.161 to 16.3.69.16616.3.69.1676
18216.3.69.168/2916.3.69.169 to 16.3.69.17416.3.69.1756
18316.3.69.176/2916.3.69.177 to 16.3.69.18216.3.69.1836
18416.3.69.184/2916.3.69.185 to 16.3.69.19016.3.69.1916
18516.3.69.192/2916.3.69.193 to 16.3.69.19816.3.69.1996
18616.3.69.200/2916.3.69.201 to 16.3.69.20616.3.69.2076
18716.3.69.208/2916.3.69.209 to 16.3.69.21416.3.69.2156
18816.3.69.216/2916.3.69.217 to 16.3.69.22216.3.69.2236
18916.3.69.224/2916.3.69.225 to 16.3.69.23016.3.69.2316
19016.3.69.232/2916.3.69.233 to 16.3.69.23816.3.69.2396
19116.3.69.240/2916.3.69.241 to 16.3.69.24616.3.69.2476
19216.3.69.248/2916.3.69.249 to 16.3.69.25416.3.69.2556
19316.3.70.0/2916.3.70.1 to 16.3.70.616.3.70.76
19416.3.70.8/2916.3.70.9 to 16.3.70.1416.3.70.156
19516.3.70.16/2916.3.70.17 to 16.3.70.2216.3.70.236
19616.3.70.24/2916.3.70.25 to 16.3.70.3016.3.70.316
19716.3.70.32/2916.3.70.33 to 16.3.70.3816.3.70.396
19816.3.70.40/2916.3.70.41 to 16.3.70.4616.3.70.476
19916.3.70.48/2916.3.70.49 to 16.3.70.5416.3.70.556
20016.3.70.56/2916.3.70.57 to 16.3.70.6216.3.70.636
20116.3.70.64/2916.3.70.65 to 16.3.70.7016.3.70.716
20216.3.70.72/2916.3.70.73 to 16.3.70.7816.3.70.796
20316.3.70.80/2916.3.70.81 to 16.3.70.8616.3.70.876
20416.3.70.88/2916.3.70.89 to 16.3.70.9416.3.70.956
20516.3.70.96/2916.3.70.97 to 16.3.70.10216.3.70.1036
20616.3.70.104/2916.3.70.105 to 16.3.70.11016.3.70.1116
20716.3.70.112/2916.3.70.113 to 16.3.70.11816.3.70.1196
20816.3.70.120/2916.3.70.121 to 16.3.70.12616.3.70.1276
20916.3.70.128/2916.3.70.129 to 16.3.70.13416.3.70.1356
21016.3.70.136/2916.3.70.137 to 16.3.70.14216.3.70.1436
21116.3.70.144/2916.3.70.145 to 16.3.70.15016.3.70.1516
21216.3.70.152/2916.3.70.153 to 16.3.70.15816.3.70.1596
21316.3.70.160/2916.3.70.161 to 16.3.70.16616.3.70.1676
21416.3.70.168/2916.3.70.169 to 16.3.70.17416.3.70.1756
21516.3.70.176/2916.3.70.177 to 16.3.70.18216.3.70.1836
21616.3.70.184/2916.3.70.185 to 16.3.70.19016.3.70.1916
21716.3.70.192/2916.3.70.193 to 16.3.70.19816.3.70.1996
21816.3.70.200/2916.3.70.201 to 16.3.70.20616.3.70.2076
21916.3.70.208/2916.3.70.209 to 16.3.70.21416.3.70.2156
22016.3.70.216/2916.3.70.217 to 16.3.70.22216.3.70.2236
22116.3.70.224/2916.3.70.225 to 16.3.70.23016.3.70.2316
22216.3.70.232/2916.3.70.233 to 16.3.70.23816.3.70.2396
22316.3.70.240/2916.3.70.241 to 16.3.70.24616.3.70.2476
22416.3.70.248/2916.3.70.249 to 16.3.70.25416.3.70.2556
22516.3.71.0/2916.3.71.1 to 16.3.71.616.3.71.76
22616.3.71.8/2916.3.71.9 to 16.3.71.1416.3.71.156
22716.3.71.16/2916.3.71.17 to 16.3.71.2216.3.71.236
22816.3.71.24/2916.3.71.25 to 16.3.71.3016.3.71.316
22916.3.71.32/2916.3.71.33 to 16.3.71.3816.3.71.396
23016.3.71.40/2916.3.71.41 to 16.3.71.4616.3.71.476
23116.3.71.48/2916.3.71.49 to 16.3.71.5416.3.71.556
23216.3.71.56/2916.3.71.57 to 16.3.71.6216.3.71.636
23316.3.71.64/2916.3.71.65 to 16.3.71.7016.3.71.716
23416.3.71.72/2916.3.71.73 to 16.3.71.7816.3.71.796
23516.3.71.80/2916.3.71.81 to 16.3.71.8616.3.71.876
23616.3.71.88/2916.3.71.89 to 16.3.71.9416.3.71.956
23716.3.71.96/2916.3.71.97 to 16.3.71.10216.3.71.1036
23816.3.71.104/2916.3.71.105 to 16.3.71.11016.3.71.1116
23916.3.71.112/2916.3.71.113 to 16.3.71.11816.3.71.1196
24016.3.71.120/2916.3.71.121 to 16.3.71.12616.3.71.1276
24116.3.71.128/2916.3.71.129 to 16.3.71.13416.3.71.1356
24216.3.71.136/2916.3.71.137 to 16.3.71.14216.3.71.1436
24316.3.71.144/2916.3.71.145 to 16.3.71.15016.3.71.1516
24416.3.71.152/2916.3.71.153 to 16.3.71.15816.3.71.1596
24516.3.71.160/2916.3.71.161 to 16.3.71.16616.3.71.1676
24616.3.71.168/2916.3.71.169 to 16.3.71.17416.3.71.1756
24716.3.71.176/2916.3.71.177 to 16.3.71.18216.3.71.1836
24816.3.71.184/2916.3.71.185 to 16.3.71.19016.3.71.1916
24916.3.71.192/2916.3.71.193 to 16.3.71.19816.3.71.1996
25016.3.71.200/2916.3.71.201 to 16.3.71.20616.3.71.2076
25116.3.71.208/2916.3.71.209 to 16.3.71.21416.3.71.2156
25216.3.71.216/2916.3.71.217 to 16.3.71.22216.3.71.2236
25316.3.71.224/2916.3.71.225 to 16.3.71.23016.3.71.2316
25416.3.71.232/2916.3.71.233 to 16.3.71.23816.3.71.2396
25516.3.71.240/2916.3.71.241 to 16.3.71.24616.3.71.2476
25616.3.71.248/2916.3.71.249 to 16.3.71.25416.3.71.2556

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.