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.

Network65.8.192.0/20
Usable hosts4,094
Subnet mask255.255.240.0
Addresses4,096
Network address
65.8.192.0
Broadcast address
65.8.207.255
First usable
65.8.192.1
Last usable
65.8.207.254
Usable hosts
4,094 (4,096 less the network and broadcast addresses)
Subnet mask
255.255.240.0
Wildcard mask
0.0.15.255 (Cisco ACLs, OSPF)
Prefix length
/20
Type
Public public
Old class
A (default /8)
As numbers
Hex 4108C000 · Integer 1091092480 to 1091096575
Reverse DNS zones
192.8.65.in-addr.arpa
193.8.65.in-addr.arpa
194.8.65.in-addr.arpa
195.8.65.in-addr.arpa
196.8.65.in-addr.arpa
197.8.65.in-addr.arpa
198.8.65.in-addr.arpa
199.8.65.in-addr.arpa
200.8.65.in-addr.arpa
201.8.65.in-addr.arpa
202.8.65.in-addr.arpa
203.8.65.in-addr.arpa
204.8.65.in-addr.arpa
205.8.65.in-addr.arpa
206.8.65.in-addr.arpa
207.8.65.in-addr.arpa
/20 is not on a 8-bit boundary, so it takes 16 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address01000001.00001000.11000000.0000000065.8.192.0
Subnet mask11111111.11111111.11110000.00000000255.255.240.0
Network01000001.00001000.11000000.0000000065.8.192.0
Broadcast01000001.00001000.11001111.1111111165.8.207.255
Split into smaller subnets/28
/21 (2)/22 (4)/23 (8)/24 (16)/25 (32)/26 (64)/27 (128)/28 (256)/29 (512)/30 (1,024)/31 (2,048)/32 (4,096)

65.8.192.0/20 makes 256 subnets of /28.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
165.8.192.0/2865.8.192.1 to 65.8.192.1465.8.192.1514
265.8.192.16/2865.8.192.17 to 65.8.192.3065.8.192.3114
365.8.192.32/2865.8.192.33 to 65.8.192.4665.8.192.4714
465.8.192.48/2865.8.192.49 to 65.8.192.6265.8.192.6314
565.8.192.64/2865.8.192.65 to 65.8.192.7865.8.192.7914
665.8.192.80/2865.8.192.81 to 65.8.192.9465.8.192.9514
765.8.192.96/2865.8.192.97 to 65.8.192.11065.8.192.11114
865.8.192.112/2865.8.192.113 to 65.8.192.12665.8.192.12714
965.8.192.128/2865.8.192.129 to 65.8.192.14265.8.192.14314
1065.8.192.144/2865.8.192.145 to 65.8.192.15865.8.192.15914
1165.8.192.160/2865.8.192.161 to 65.8.192.17465.8.192.17514
1265.8.192.176/2865.8.192.177 to 65.8.192.19065.8.192.19114
1365.8.192.192/2865.8.192.193 to 65.8.192.20665.8.192.20714
1465.8.192.208/2865.8.192.209 to 65.8.192.22265.8.192.22314
1565.8.192.224/2865.8.192.225 to 65.8.192.23865.8.192.23914
1665.8.192.240/2865.8.192.241 to 65.8.192.25465.8.192.25514
1765.8.193.0/2865.8.193.1 to 65.8.193.1465.8.193.1514
1865.8.193.16/2865.8.193.17 to 65.8.193.3065.8.193.3114
1965.8.193.32/2865.8.193.33 to 65.8.193.4665.8.193.4714
2065.8.193.48/2865.8.193.49 to 65.8.193.6265.8.193.6314
2165.8.193.64/2865.8.193.65 to 65.8.193.7865.8.193.7914
2265.8.193.80/2865.8.193.81 to 65.8.193.9465.8.193.9514
2365.8.193.96/2865.8.193.97 to 65.8.193.11065.8.193.11114
2465.8.193.112/2865.8.193.113 to 65.8.193.12665.8.193.12714
2565.8.193.128/2865.8.193.129 to 65.8.193.14265.8.193.14314
2665.8.193.144/2865.8.193.145 to 65.8.193.15865.8.193.15914
2765.8.193.160/2865.8.193.161 to 65.8.193.17465.8.193.17514
2865.8.193.176/2865.8.193.177 to 65.8.193.19065.8.193.19114
2965.8.193.192/2865.8.193.193 to 65.8.193.20665.8.193.20714
3065.8.193.208/2865.8.193.209 to 65.8.193.22265.8.193.22314
3165.8.193.224/2865.8.193.225 to 65.8.193.23865.8.193.23914
3265.8.193.240/2865.8.193.241 to 65.8.193.25465.8.193.25514
3365.8.194.0/2865.8.194.1 to 65.8.194.1465.8.194.1514
3465.8.194.16/2865.8.194.17 to 65.8.194.3065.8.194.3114
3565.8.194.32/2865.8.194.33 to 65.8.194.4665.8.194.4714
3665.8.194.48/2865.8.194.49 to 65.8.194.6265.8.194.6314
3765.8.194.64/2865.8.194.65 to 65.8.194.7865.8.194.7914
3865.8.194.80/2865.8.194.81 to 65.8.194.9465.8.194.9514
3965.8.194.96/2865.8.194.97 to 65.8.194.11065.8.194.11114
4065.8.194.112/2865.8.194.113 to 65.8.194.12665.8.194.12714
4165.8.194.128/2865.8.194.129 to 65.8.194.14265.8.194.14314
4265.8.194.144/2865.8.194.145 to 65.8.194.15865.8.194.15914
4365.8.194.160/2865.8.194.161 to 65.8.194.17465.8.194.17514
4465.8.194.176/2865.8.194.177 to 65.8.194.19065.8.194.19114
4565.8.194.192/2865.8.194.193 to 65.8.194.20665.8.194.20714
4665.8.194.208/2865.8.194.209 to 65.8.194.22265.8.194.22314
4765.8.194.224/2865.8.194.225 to 65.8.194.23865.8.194.23914
4865.8.194.240/2865.8.194.241 to 65.8.194.25465.8.194.25514
4965.8.195.0/2865.8.195.1 to 65.8.195.1465.8.195.1514
5065.8.195.16/2865.8.195.17 to 65.8.195.3065.8.195.3114
5165.8.195.32/2865.8.195.33 to 65.8.195.4665.8.195.4714
5265.8.195.48/2865.8.195.49 to 65.8.195.6265.8.195.6314
5365.8.195.64/2865.8.195.65 to 65.8.195.7865.8.195.7914
5465.8.195.80/2865.8.195.81 to 65.8.195.9465.8.195.9514
5565.8.195.96/2865.8.195.97 to 65.8.195.11065.8.195.11114
5665.8.195.112/2865.8.195.113 to 65.8.195.12665.8.195.12714
5765.8.195.128/2865.8.195.129 to 65.8.195.14265.8.195.14314
5865.8.195.144/2865.8.195.145 to 65.8.195.15865.8.195.15914
5965.8.195.160/2865.8.195.161 to 65.8.195.17465.8.195.17514
6065.8.195.176/2865.8.195.177 to 65.8.195.19065.8.195.19114
6165.8.195.192/2865.8.195.193 to 65.8.195.20665.8.195.20714
6265.8.195.208/2865.8.195.209 to 65.8.195.22265.8.195.22314
6365.8.195.224/2865.8.195.225 to 65.8.195.23865.8.195.23914
6465.8.195.240/2865.8.195.241 to 65.8.195.25465.8.195.25514
6565.8.196.0/2865.8.196.1 to 65.8.196.1465.8.196.1514
6665.8.196.16/2865.8.196.17 to 65.8.196.3065.8.196.3114
6765.8.196.32/2865.8.196.33 to 65.8.196.4665.8.196.4714
6865.8.196.48/2865.8.196.49 to 65.8.196.6265.8.196.6314
6965.8.196.64/2865.8.196.65 to 65.8.196.7865.8.196.7914
7065.8.196.80/2865.8.196.81 to 65.8.196.9465.8.196.9514
7165.8.196.96/2865.8.196.97 to 65.8.196.11065.8.196.11114
7265.8.196.112/2865.8.196.113 to 65.8.196.12665.8.196.12714
7365.8.196.128/2865.8.196.129 to 65.8.196.14265.8.196.14314
7465.8.196.144/2865.8.196.145 to 65.8.196.15865.8.196.15914
7565.8.196.160/2865.8.196.161 to 65.8.196.17465.8.196.17514
7665.8.196.176/2865.8.196.177 to 65.8.196.19065.8.196.19114
7765.8.196.192/2865.8.196.193 to 65.8.196.20665.8.196.20714
7865.8.196.208/2865.8.196.209 to 65.8.196.22265.8.196.22314
7965.8.196.224/2865.8.196.225 to 65.8.196.23865.8.196.23914
8065.8.196.240/2865.8.196.241 to 65.8.196.25465.8.196.25514
8165.8.197.0/2865.8.197.1 to 65.8.197.1465.8.197.1514
8265.8.197.16/2865.8.197.17 to 65.8.197.3065.8.197.3114
8365.8.197.32/2865.8.197.33 to 65.8.197.4665.8.197.4714
8465.8.197.48/2865.8.197.49 to 65.8.197.6265.8.197.6314
8565.8.197.64/2865.8.197.65 to 65.8.197.7865.8.197.7914
8665.8.197.80/2865.8.197.81 to 65.8.197.9465.8.197.9514
8765.8.197.96/2865.8.197.97 to 65.8.197.11065.8.197.11114
8865.8.197.112/2865.8.197.113 to 65.8.197.12665.8.197.12714
8965.8.197.128/2865.8.197.129 to 65.8.197.14265.8.197.14314
9065.8.197.144/2865.8.197.145 to 65.8.197.15865.8.197.15914
9165.8.197.160/2865.8.197.161 to 65.8.197.17465.8.197.17514
9265.8.197.176/2865.8.197.177 to 65.8.197.19065.8.197.19114
9365.8.197.192/2865.8.197.193 to 65.8.197.20665.8.197.20714
9465.8.197.208/2865.8.197.209 to 65.8.197.22265.8.197.22314
9565.8.197.224/2865.8.197.225 to 65.8.197.23865.8.197.23914
9665.8.197.240/2865.8.197.241 to 65.8.197.25465.8.197.25514
9765.8.198.0/2865.8.198.1 to 65.8.198.1465.8.198.1514
9865.8.198.16/2865.8.198.17 to 65.8.198.3065.8.198.3114
9965.8.198.32/2865.8.198.33 to 65.8.198.4665.8.198.4714
10065.8.198.48/2865.8.198.49 to 65.8.198.6265.8.198.6314
10165.8.198.64/2865.8.198.65 to 65.8.198.7865.8.198.7914
10265.8.198.80/2865.8.198.81 to 65.8.198.9465.8.198.9514
10365.8.198.96/2865.8.198.97 to 65.8.198.11065.8.198.11114
10465.8.198.112/2865.8.198.113 to 65.8.198.12665.8.198.12714
10565.8.198.128/2865.8.198.129 to 65.8.198.14265.8.198.14314
10665.8.198.144/2865.8.198.145 to 65.8.198.15865.8.198.15914
10765.8.198.160/2865.8.198.161 to 65.8.198.17465.8.198.17514
10865.8.198.176/2865.8.198.177 to 65.8.198.19065.8.198.19114
10965.8.198.192/2865.8.198.193 to 65.8.198.20665.8.198.20714
11065.8.198.208/2865.8.198.209 to 65.8.198.22265.8.198.22314
11165.8.198.224/2865.8.198.225 to 65.8.198.23865.8.198.23914
11265.8.198.240/2865.8.198.241 to 65.8.198.25465.8.198.25514
11365.8.199.0/2865.8.199.1 to 65.8.199.1465.8.199.1514
11465.8.199.16/2865.8.199.17 to 65.8.199.3065.8.199.3114
11565.8.199.32/2865.8.199.33 to 65.8.199.4665.8.199.4714
11665.8.199.48/2865.8.199.49 to 65.8.199.6265.8.199.6314
11765.8.199.64/2865.8.199.65 to 65.8.199.7865.8.199.7914
11865.8.199.80/2865.8.199.81 to 65.8.199.9465.8.199.9514
11965.8.199.96/2865.8.199.97 to 65.8.199.11065.8.199.11114
12065.8.199.112/2865.8.199.113 to 65.8.199.12665.8.199.12714
12165.8.199.128/2865.8.199.129 to 65.8.199.14265.8.199.14314
12265.8.199.144/2865.8.199.145 to 65.8.199.15865.8.199.15914
12365.8.199.160/2865.8.199.161 to 65.8.199.17465.8.199.17514
12465.8.199.176/2865.8.199.177 to 65.8.199.19065.8.199.19114
12565.8.199.192/2865.8.199.193 to 65.8.199.20665.8.199.20714
12665.8.199.208/2865.8.199.209 to 65.8.199.22265.8.199.22314
12765.8.199.224/2865.8.199.225 to 65.8.199.23865.8.199.23914
12865.8.199.240/2865.8.199.241 to 65.8.199.25465.8.199.25514
12965.8.200.0/2865.8.200.1 to 65.8.200.1465.8.200.1514
13065.8.200.16/2865.8.200.17 to 65.8.200.3065.8.200.3114
13165.8.200.32/2865.8.200.33 to 65.8.200.4665.8.200.4714
13265.8.200.48/2865.8.200.49 to 65.8.200.6265.8.200.6314
13365.8.200.64/2865.8.200.65 to 65.8.200.7865.8.200.7914
13465.8.200.80/2865.8.200.81 to 65.8.200.9465.8.200.9514
13565.8.200.96/2865.8.200.97 to 65.8.200.11065.8.200.11114
13665.8.200.112/2865.8.200.113 to 65.8.200.12665.8.200.12714
13765.8.200.128/2865.8.200.129 to 65.8.200.14265.8.200.14314
13865.8.200.144/2865.8.200.145 to 65.8.200.15865.8.200.15914
13965.8.200.160/2865.8.200.161 to 65.8.200.17465.8.200.17514
14065.8.200.176/2865.8.200.177 to 65.8.200.19065.8.200.19114
14165.8.200.192/2865.8.200.193 to 65.8.200.20665.8.200.20714
14265.8.200.208/2865.8.200.209 to 65.8.200.22265.8.200.22314
14365.8.200.224/2865.8.200.225 to 65.8.200.23865.8.200.23914
14465.8.200.240/2865.8.200.241 to 65.8.200.25465.8.200.25514
14565.8.201.0/2865.8.201.1 to 65.8.201.1465.8.201.1514
14665.8.201.16/2865.8.201.17 to 65.8.201.3065.8.201.3114
14765.8.201.32/2865.8.201.33 to 65.8.201.4665.8.201.4714
14865.8.201.48/2865.8.201.49 to 65.8.201.6265.8.201.6314
14965.8.201.64/2865.8.201.65 to 65.8.201.7865.8.201.7914
15065.8.201.80/2865.8.201.81 to 65.8.201.9465.8.201.9514
15165.8.201.96/2865.8.201.97 to 65.8.201.11065.8.201.11114
15265.8.201.112/2865.8.201.113 to 65.8.201.12665.8.201.12714
15365.8.201.128/2865.8.201.129 to 65.8.201.14265.8.201.14314
15465.8.201.144/2865.8.201.145 to 65.8.201.15865.8.201.15914
15565.8.201.160/2865.8.201.161 to 65.8.201.17465.8.201.17514
15665.8.201.176/2865.8.201.177 to 65.8.201.19065.8.201.19114
15765.8.201.192/2865.8.201.193 to 65.8.201.20665.8.201.20714
15865.8.201.208/2865.8.201.209 to 65.8.201.22265.8.201.22314
15965.8.201.224/2865.8.201.225 to 65.8.201.23865.8.201.23914
16065.8.201.240/2865.8.201.241 to 65.8.201.25465.8.201.25514
16165.8.202.0/2865.8.202.1 to 65.8.202.1465.8.202.1514
16265.8.202.16/2865.8.202.17 to 65.8.202.3065.8.202.3114
16365.8.202.32/2865.8.202.33 to 65.8.202.4665.8.202.4714
16465.8.202.48/2865.8.202.49 to 65.8.202.6265.8.202.6314
16565.8.202.64/2865.8.202.65 to 65.8.202.7865.8.202.7914
16665.8.202.80/2865.8.202.81 to 65.8.202.9465.8.202.9514
16765.8.202.96/2865.8.202.97 to 65.8.202.11065.8.202.11114
16865.8.202.112/2865.8.202.113 to 65.8.202.12665.8.202.12714
16965.8.202.128/2865.8.202.129 to 65.8.202.14265.8.202.14314
17065.8.202.144/2865.8.202.145 to 65.8.202.15865.8.202.15914
17165.8.202.160/2865.8.202.161 to 65.8.202.17465.8.202.17514
17265.8.202.176/2865.8.202.177 to 65.8.202.19065.8.202.19114
17365.8.202.192/2865.8.202.193 to 65.8.202.20665.8.202.20714
17465.8.202.208/2865.8.202.209 to 65.8.202.22265.8.202.22314
17565.8.202.224/2865.8.202.225 to 65.8.202.23865.8.202.23914
17665.8.202.240/2865.8.202.241 to 65.8.202.25465.8.202.25514
17765.8.203.0/2865.8.203.1 to 65.8.203.1465.8.203.1514
17865.8.203.16/2865.8.203.17 to 65.8.203.3065.8.203.3114
17965.8.203.32/2865.8.203.33 to 65.8.203.4665.8.203.4714
18065.8.203.48/2865.8.203.49 to 65.8.203.6265.8.203.6314
18165.8.203.64/2865.8.203.65 to 65.8.203.7865.8.203.7914
18265.8.203.80/2865.8.203.81 to 65.8.203.9465.8.203.9514
18365.8.203.96/2865.8.203.97 to 65.8.203.11065.8.203.11114
18465.8.203.112/2865.8.203.113 to 65.8.203.12665.8.203.12714
18565.8.203.128/2865.8.203.129 to 65.8.203.14265.8.203.14314
18665.8.203.144/2865.8.203.145 to 65.8.203.15865.8.203.15914
18765.8.203.160/2865.8.203.161 to 65.8.203.17465.8.203.17514
18865.8.203.176/2865.8.203.177 to 65.8.203.19065.8.203.19114
18965.8.203.192/2865.8.203.193 to 65.8.203.20665.8.203.20714
19065.8.203.208/2865.8.203.209 to 65.8.203.22265.8.203.22314
19165.8.203.224/2865.8.203.225 to 65.8.203.23865.8.203.23914
19265.8.203.240/2865.8.203.241 to 65.8.203.25465.8.203.25514
19365.8.204.0/2865.8.204.1 to 65.8.204.1465.8.204.1514
19465.8.204.16/2865.8.204.17 to 65.8.204.3065.8.204.3114
19565.8.204.32/2865.8.204.33 to 65.8.204.4665.8.204.4714
19665.8.204.48/2865.8.204.49 to 65.8.204.6265.8.204.6314
19765.8.204.64/2865.8.204.65 to 65.8.204.7865.8.204.7914
19865.8.204.80/2865.8.204.81 to 65.8.204.9465.8.204.9514
19965.8.204.96/2865.8.204.97 to 65.8.204.11065.8.204.11114
20065.8.204.112/2865.8.204.113 to 65.8.204.12665.8.204.12714
20165.8.204.128/2865.8.204.129 to 65.8.204.14265.8.204.14314
20265.8.204.144/2865.8.204.145 to 65.8.204.15865.8.204.15914
20365.8.204.160/2865.8.204.161 to 65.8.204.17465.8.204.17514
20465.8.204.176/2865.8.204.177 to 65.8.204.19065.8.204.19114
20565.8.204.192/2865.8.204.193 to 65.8.204.20665.8.204.20714
20665.8.204.208/2865.8.204.209 to 65.8.204.22265.8.204.22314
20765.8.204.224/2865.8.204.225 to 65.8.204.23865.8.204.23914
20865.8.204.240/2865.8.204.241 to 65.8.204.25465.8.204.25514
20965.8.205.0/2865.8.205.1 to 65.8.205.1465.8.205.1514
21065.8.205.16/2865.8.205.17 to 65.8.205.3065.8.205.3114
21165.8.205.32/2865.8.205.33 to 65.8.205.4665.8.205.4714
21265.8.205.48/2865.8.205.49 to 65.8.205.6265.8.205.6314
21365.8.205.64/2865.8.205.65 to 65.8.205.7865.8.205.7914
21465.8.205.80/2865.8.205.81 to 65.8.205.9465.8.205.9514
21565.8.205.96/2865.8.205.97 to 65.8.205.11065.8.205.11114
21665.8.205.112/2865.8.205.113 to 65.8.205.12665.8.205.12714
21765.8.205.128/2865.8.205.129 to 65.8.205.14265.8.205.14314
21865.8.205.144/2865.8.205.145 to 65.8.205.15865.8.205.15914
21965.8.205.160/2865.8.205.161 to 65.8.205.17465.8.205.17514
22065.8.205.176/2865.8.205.177 to 65.8.205.19065.8.205.19114
22165.8.205.192/2865.8.205.193 to 65.8.205.20665.8.205.20714
22265.8.205.208/2865.8.205.209 to 65.8.205.22265.8.205.22314
22365.8.205.224/2865.8.205.225 to 65.8.205.23865.8.205.23914
22465.8.205.240/2865.8.205.241 to 65.8.205.25465.8.205.25514
22565.8.206.0/2865.8.206.1 to 65.8.206.1465.8.206.1514
22665.8.206.16/2865.8.206.17 to 65.8.206.3065.8.206.3114
22765.8.206.32/2865.8.206.33 to 65.8.206.4665.8.206.4714
22865.8.206.48/2865.8.206.49 to 65.8.206.6265.8.206.6314
22965.8.206.64/2865.8.206.65 to 65.8.206.7865.8.206.7914
23065.8.206.80/2865.8.206.81 to 65.8.206.9465.8.206.9514
23165.8.206.96/2865.8.206.97 to 65.8.206.11065.8.206.11114
23265.8.206.112/2865.8.206.113 to 65.8.206.12665.8.206.12714
23365.8.206.128/2865.8.206.129 to 65.8.206.14265.8.206.14314
23465.8.206.144/2865.8.206.145 to 65.8.206.15865.8.206.15914
23565.8.206.160/2865.8.206.161 to 65.8.206.17465.8.206.17514
23665.8.206.176/2865.8.206.177 to 65.8.206.19065.8.206.19114
23765.8.206.192/2865.8.206.193 to 65.8.206.20665.8.206.20714
23865.8.206.208/2865.8.206.209 to 65.8.206.22265.8.206.22314
23965.8.206.224/2865.8.206.225 to 65.8.206.23865.8.206.23914
24065.8.206.240/2865.8.206.241 to 65.8.206.25465.8.206.25514
24165.8.207.0/2865.8.207.1 to 65.8.207.1465.8.207.1514
24265.8.207.16/2865.8.207.17 to 65.8.207.3065.8.207.3114
24365.8.207.32/2865.8.207.33 to 65.8.207.4665.8.207.4714
24465.8.207.48/2865.8.207.49 to 65.8.207.6265.8.207.6314
24565.8.207.64/2865.8.207.65 to 65.8.207.7865.8.207.7914
24665.8.207.80/2865.8.207.81 to 65.8.207.9465.8.207.9514
24765.8.207.96/2865.8.207.97 to 65.8.207.11065.8.207.11114
24865.8.207.112/2865.8.207.113 to 65.8.207.12665.8.207.12714
24965.8.207.128/2865.8.207.129 to 65.8.207.14265.8.207.14314
25065.8.207.144/2865.8.207.145 to 65.8.207.15865.8.207.15914
25165.8.207.160/2865.8.207.161 to 65.8.207.17465.8.207.17514
25265.8.207.176/2865.8.207.177 to 65.8.207.19065.8.207.19114
25365.8.207.192/2865.8.207.193 to 65.8.207.20665.8.207.20714
25465.8.207.208/2865.8.207.209 to 65.8.207.22265.8.207.22314
25565.8.207.224/2865.8.207.225 to 65.8.207.23865.8.207.23914
25665.8.207.240/2865.8.207.241 to 65.8.207.25465.8.207.25514

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.