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.

Network55.128.0.0/10
Usable hosts4,194,302
Subnet mask255.192.0.0
Addresses4,194,304
Network address
55.128.0.0
Broadcast address
55.191.255.255
First usable
55.128.0.1
Last usable
55.191.255.254
Usable hosts
4,194,302 (4,194,304 less the network and broadcast addresses)
Subnet mask
255.192.0.0
Wildcard mask
0.63.255.255 (Cisco ACLs, OSPF)
Prefix length
/10
Type
Public public
Old class
A (default /8)
As numbers
Hex 37800000 · Integer 931135488 to 935329791
Reverse DNS zones
128.55.in-addr.arpa
129.55.in-addr.arpa
130.55.in-addr.arpa
131.55.in-addr.arpa
132.55.in-addr.arpa
133.55.in-addr.arpa
134.55.in-addr.arpa
135.55.in-addr.arpa
136.55.in-addr.arpa
137.55.in-addr.arpa
138.55.in-addr.arpa
139.55.in-addr.arpa
140.55.in-addr.arpa
141.55.in-addr.arpa
142.55.in-addr.arpa
143.55.in-addr.arpa
and 48 more
/10 is not on a 8-bit boundary, so it takes 64 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00110111.10000000.00000000.0000000055.128.0.0
Subnet mask11111111.11000000.00000000.00000000255.192.0.0
Network00110111.10000000.00000000.0000000055.128.0.0
Broadcast00110111.10111111.11111111.1111111155.191.255.255
Split into smaller subnets/21
/11 (2)/12 (4)/13 (8)/14 (16)/15 (32)/16 (64)/17 (128)/18 (256)/19 (512)/20 (1,024)/21 (2,048)/22 (4,096)

55.128.0.0/10 makes 2,048 subnets of /21; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
155.128.0.0/2155.128.0.1 to 55.128.7.25455.128.7.2552,046
255.128.8.0/2155.128.8.1 to 55.128.15.25455.128.15.2552,046
355.128.16.0/2155.128.16.1 to 55.128.23.25455.128.23.2552,046
455.128.24.0/2155.128.24.1 to 55.128.31.25455.128.31.2552,046
555.128.32.0/2155.128.32.1 to 55.128.39.25455.128.39.2552,046
655.128.40.0/2155.128.40.1 to 55.128.47.25455.128.47.2552,046
755.128.48.0/2155.128.48.1 to 55.128.55.25455.128.55.2552,046
855.128.56.0/2155.128.56.1 to 55.128.63.25455.128.63.2552,046
955.128.64.0/2155.128.64.1 to 55.128.71.25455.128.71.2552,046
1055.128.72.0/2155.128.72.1 to 55.128.79.25455.128.79.2552,046
1155.128.80.0/2155.128.80.1 to 55.128.87.25455.128.87.2552,046
1255.128.88.0/2155.128.88.1 to 55.128.95.25455.128.95.2552,046
1355.128.96.0/2155.128.96.1 to 55.128.103.25455.128.103.2552,046
1455.128.104.0/2155.128.104.1 to 55.128.111.25455.128.111.2552,046
1555.128.112.0/2155.128.112.1 to 55.128.119.25455.128.119.2552,046
1655.128.120.0/2155.128.120.1 to 55.128.127.25455.128.127.2552,046
1755.128.128.0/2155.128.128.1 to 55.128.135.25455.128.135.2552,046
1855.128.136.0/2155.128.136.1 to 55.128.143.25455.128.143.2552,046
1955.128.144.0/2155.128.144.1 to 55.128.151.25455.128.151.2552,046
2055.128.152.0/2155.128.152.1 to 55.128.159.25455.128.159.2552,046
2155.128.160.0/2155.128.160.1 to 55.128.167.25455.128.167.2552,046
2255.128.168.0/2155.128.168.1 to 55.128.175.25455.128.175.2552,046
2355.128.176.0/2155.128.176.1 to 55.128.183.25455.128.183.2552,046
2455.128.184.0/2155.128.184.1 to 55.128.191.25455.128.191.2552,046
2555.128.192.0/2155.128.192.1 to 55.128.199.25455.128.199.2552,046
2655.128.200.0/2155.128.200.1 to 55.128.207.25455.128.207.2552,046
2755.128.208.0/2155.128.208.1 to 55.128.215.25455.128.215.2552,046
2855.128.216.0/2155.128.216.1 to 55.128.223.25455.128.223.2552,046
2955.128.224.0/2155.128.224.1 to 55.128.231.25455.128.231.2552,046
3055.128.232.0/2155.128.232.1 to 55.128.239.25455.128.239.2552,046
3155.128.240.0/2155.128.240.1 to 55.128.247.25455.128.247.2552,046
3255.128.248.0/2155.128.248.1 to 55.128.255.25455.128.255.2552,046
3355.129.0.0/2155.129.0.1 to 55.129.7.25455.129.7.2552,046
3455.129.8.0/2155.129.8.1 to 55.129.15.25455.129.15.2552,046
3555.129.16.0/2155.129.16.1 to 55.129.23.25455.129.23.2552,046
3655.129.24.0/2155.129.24.1 to 55.129.31.25455.129.31.2552,046
3755.129.32.0/2155.129.32.1 to 55.129.39.25455.129.39.2552,046
3855.129.40.0/2155.129.40.1 to 55.129.47.25455.129.47.2552,046
3955.129.48.0/2155.129.48.1 to 55.129.55.25455.129.55.2552,046
4055.129.56.0/2155.129.56.1 to 55.129.63.25455.129.63.2552,046
4155.129.64.0/2155.129.64.1 to 55.129.71.25455.129.71.2552,046
4255.129.72.0/2155.129.72.1 to 55.129.79.25455.129.79.2552,046
4355.129.80.0/2155.129.80.1 to 55.129.87.25455.129.87.2552,046
4455.129.88.0/2155.129.88.1 to 55.129.95.25455.129.95.2552,046
4555.129.96.0/2155.129.96.1 to 55.129.103.25455.129.103.2552,046
4655.129.104.0/2155.129.104.1 to 55.129.111.25455.129.111.2552,046
4755.129.112.0/2155.129.112.1 to 55.129.119.25455.129.119.2552,046
4855.129.120.0/2155.129.120.1 to 55.129.127.25455.129.127.2552,046
4955.129.128.0/2155.129.128.1 to 55.129.135.25455.129.135.2552,046
5055.129.136.0/2155.129.136.1 to 55.129.143.25455.129.143.2552,046
5155.129.144.0/2155.129.144.1 to 55.129.151.25455.129.151.2552,046
5255.129.152.0/2155.129.152.1 to 55.129.159.25455.129.159.2552,046
5355.129.160.0/2155.129.160.1 to 55.129.167.25455.129.167.2552,046
5455.129.168.0/2155.129.168.1 to 55.129.175.25455.129.175.2552,046
5555.129.176.0/2155.129.176.1 to 55.129.183.25455.129.183.2552,046
5655.129.184.0/2155.129.184.1 to 55.129.191.25455.129.191.2552,046
5755.129.192.0/2155.129.192.1 to 55.129.199.25455.129.199.2552,046
5855.129.200.0/2155.129.200.1 to 55.129.207.25455.129.207.2552,046
5955.129.208.0/2155.129.208.1 to 55.129.215.25455.129.215.2552,046
6055.129.216.0/2155.129.216.1 to 55.129.223.25455.129.223.2552,046
6155.129.224.0/2155.129.224.1 to 55.129.231.25455.129.231.2552,046
6255.129.232.0/2155.129.232.1 to 55.129.239.25455.129.239.2552,046
6355.129.240.0/2155.129.240.1 to 55.129.247.25455.129.247.2552,046
6455.129.248.0/2155.129.248.1 to 55.129.255.25455.129.255.2552,046
6555.130.0.0/2155.130.0.1 to 55.130.7.25455.130.7.2552,046
6655.130.8.0/2155.130.8.1 to 55.130.15.25455.130.15.2552,046
6755.130.16.0/2155.130.16.1 to 55.130.23.25455.130.23.2552,046
6855.130.24.0/2155.130.24.1 to 55.130.31.25455.130.31.2552,046
6955.130.32.0/2155.130.32.1 to 55.130.39.25455.130.39.2552,046
7055.130.40.0/2155.130.40.1 to 55.130.47.25455.130.47.2552,046
7155.130.48.0/2155.130.48.1 to 55.130.55.25455.130.55.2552,046
7255.130.56.0/2155.130.56.1 to 55.130.63.25455.130.63.2552,046
7355.130.64.0/2155.130.64.1 to 55.130.71.25455.130.71.2552,046
7455.130.72.0/2155.130.72.1 to 55.130.79.25455.130.79.2552,046
7555.130.80.0/2155.130.80.1 to 55.130.87.25455.130.87.2552,046
7655.130.88.0/2155.130.88.1 to 55.130.95.25455.130.95.2552,046
7755.130.96.0/2155.130.96.1 to 55.130.103.25455.130.103.2552,046
7855.130.104.0/2155.130.104.1 to 55.130.111.25455.130.111.2552,046
7955.130.112.0/2155.130.112.1 to 55.130.119.25455.130.119.2552,046
8055.130.120.0/2155.130.120.1 to 55.130.127.25455.130.127.2552,046
8155.130.128.0/2155.130.128.1 to 55.130.135.25455.130.135.2552,046
8255.130.136.0/2155.130.136.1 to 55.130.143.25455.130.143.2552,046
8355.130.144.0/2155.130.144.1 to 55.130.151.25455.130.151.2552,046
8455.130.152.0/2155.130.152.1 to 55.130.159.25455.130.159.2552,046
8555.130.160.0/2155.130.160.1 to 55.130.167.25455.130.167.2552,046
8655.130.168.0/2155.130.168.1 to 55.130.175.25455.130.175.2552,046
8755.130.176.0/2155.130.176.1 to 55.130.183.25455.130.183.2552,046
8855.130.184.0/2155.130.184.1 to 55.130.191.25455.130.191.2552,046
8955.130.192.0/2155.130.192.1 to 55.130.199.25455.130.199.2552,046
9055.130.200.0/2155.130.200.1 to 55.130.207.25455.130.207.2552,046
9155.130.208.0/2155.130.208.1 to 55.130.215.25455.130.215.2552,046
9255.130.216.0/2155.130.216.1 to 55.130.223.25455.130.223.2552,046
9355.130.224.0/2155.130.224.1 to 55.130.231.25455.130.231.2552,046
9455.130.232.0/2155.130.232.1 to 55.130.239.25455.130.239.2552,046
9555.130.240.0/2155.130.240.1 to 55.130.247.25455.130.247.2552,046
9655.130.248.0/2155.130.248.1 to 55.130.255.25455.130.255.2552,046
9755.131.0.0/2155.131.0.1 to 55.131.7.25455.131.7.2552,046
9855.131.8.0/2155.131.8.1 to 55.131.15.25455.131.15.2552,046
9955.131.16.0/2155.131.16.1 to 55.131.23.25455.131.23.2552,046
10055.131.24.0/2155.131.24.1 to 55.131.31.25455.131.31.2552,046
10155.131.32.0/2155.131.32.1 to 55.131.39.25455.131.39.2552,046
10255.131.40.0/2155.131.40.1 to 55.131.47.25455.131.47.2552,046
10355.131.48.0/2155.131.48.1 to 55.131.55.25455.131.55.2552,046
10455.131.56.0/2155.131.56.1 to 55.131.63.25455.131.63.2552,046
10555.131.64.0/2155.131.64.1 to 55.131.71.25455.131.71.2552,046
10655.131.72.0/2155.131.72.1 to 55.131.79.25455.131.79.2552,046
10755.131.80.0/2155.131.80.1 to 55.131.87.25455.131.87.2552,046
10855.131.88.0/2155.131.88.1 to 55.131.95.25455.131.95.2552,046
10955.131.96.0/2155.131.96.1 to 55.131.103.25455.131.103.2552,046
11055.131.104.0/2155.131.104.1 to 55.131.111.25455.131.111.2552,046
11155.131.112.0/2155.131.112.1 to 55.131.119.25455.131.119.2552,046
11255.131.120.0/2155.131.120.1 to 55.131.127.25455.131.127.2552,046
11355.131.128.0/2155.131.128.1 to 55.131.135.25455.131.135.2552,046
11455.131.136.0/2155.131.136.1 to 55.131.143.25455.131.143.2552,046
11555.131.144.0/2155.131.144.1 to 55.131.151.25455.131.151.2552,046
11655.131.152.0/2155.131.152.1 to 55.131.159.25455.131.159.2552,046
11755.131.160.0/2155.131.160.1 to 55.131.167.25455.131.167.2552,046
11855.131.168.0/2155.131.168.1 to 55.131.175.25455.131.175.2552,046
11955.131.176.0/2155.131.176.1 to 55.131.183.25455.131.183.2552,046
12055.131.184.0/2155.131.184.1 to 55.131.191.25455.131.191.2552,046
12155.131.192.0/2155.131.192.1 to 55.131.199.25455.131.199.2552,046
12255.131.200.0/2155.131.200.1 to 55.131.207.25455.131.207.2552,046
12355.131.208.0/2155.131.208.1 to 55.131.215.25455.131.215.2552,046
12455.131.216.0/2155.131.216.1 to 55.131.223.25455.131.223.2552,046
12555.131.224.0/2155.131.224.1 to 55.131.231.25455.131.231.2552,046
12655.131.232.0/2155.131.232.1 to 55.131.239.25455.131.239.2552,046
12755.131.240.0/2155.131.240.1 to 55.131.247.25455.131.247.2552,046
12855.131.248.0/2155.131.248.1 to 55.131.255.25455.131.255.2552,046
12955.132.0.0/2155.132.0.1 to 55.132.7.25455.132.7.2552,046
13055.132.8.0/2155.132.8.1 to 55.132.15.25455.132.15.2552,046
13155.132.16.0/2155.132.16.1 to 55.132.23.25455.132.23.2552,046
13255.132.24.0/2155.132.24.1 to 55.132.31.25455.132.31.2552,046
13355.132.32.0/2155.132.32.1 to 55.132.39.25455.132.39.2552,046
13455.132.40.0/2155.132.40.1 to 55.132.47.25455.132.47.2552,046
13555.132.48.0/2155.132.48.1 to 55.132.55.25455.132.55.2552,046
13655.132.56.0/2155.132.56.1 to 55.132.63.25455.132.63.2552,046
13755.132.64.0/2155.132.64.1 to 55.132.71.25455.132.71.2552,046
13855.132.72.0/2155.132.72.1 to 55.132.79.25455.132.79.2552,046
13955.132.80.0/2155.132.80.1 to 55.132.87.25455.132.87.2552,046
14055.132.88.0/2155.132.88.1 to 55.132.95.25455.132.95.2552,046
14155.132.96.0/2155.132.96.1 to 55.132.103.25455.132.103.2552,046
14255.132.104.0/2155.132.104.1 to 55.132.111.25455.132.111.2552,046
14355.132.112.0/2155.132.112.1 to 55.132.119.25455.132.119.2552,046
14455.132.120.0/2155.132.120.1 to 55.132.127.25455.132.127.2552,046
14555.132.128.0/2155.132.128.1 to 55.132.135.25455.132.135.2552,046
14655.132.136.0/2155.132.136.1 to 55.132.143.25455.132.143.2552,046
14755.132.144.0/2155.132.144.1 to 55.132.151.25455.132.151.2552,046
14855.132.152.0/2155.132.152.1 to 55.132.159.25455.132.159.2552,046
14955.132.160.0/2155.132.160.1 to 55.132.167.25455.132.167.2552,046
15055.132.168.0/2155.132.168.1 to 55.132.175.25455.132.175.2552,046
15155.132.176.0/2155.132.176.1 to 55.132.183.25455.132.183.2552,046
15255.132.184.0/2155.132.184.1 to 55.132.191.25455.132.191.2552,046
15355.132.192.0/2155.132.192.1 to 55.132.199.25455.132.199.2552,046
15455.132.200.0/2155.132.200.1 to 55.132.207.25455.132.207.2552,046
15555.132.208.0/2155.132.208.1 to 55.132.215.25455.132.215.2552,046
15655.132.216.0/2155.132.216.1 to 55.132.223.25455.132.223.2552,046
15755.132.224.0/2155.132.224.1 to 55.132.231.25455.132.231.2552,046
15855.132.232.0/2155.132.232.1 to 55.132.239.25455.132.239.2552,046
15955.132.240.0/2155.132.240.1 to 55.132.247.25455.132.247.2552,046
16055.132.248.0/2155.132.248.1 to 55.132.255.25455.132.255.2552,046
16155.133.0.0/2155.133.0.1 to 55.133.7.25455.133.7.2552,046
16255.133.8.0/2155.133.8.1 to 55.133.15.25455.133.15.2552,046
16355.133.16.0/2155.133.16.1 to 55.133.23.25455.133.23.2552,046
16455.133.24.0/2155.133.24.1 to 55.133.31.25455.133.31.2552,046
16555.133.32.0/2155.133.32.1 to 55.133.39.25455.133.39.2552,046
16655.133.40.0/2155.133.40.1 to 55.133.47.25455.133.47.2552,046
16755.133.48.0/2155.133.48.1 to 55.133.55.25455.133.55.2552,046
16855.133.56.0/2155.133.56.1 to 55.133.63.25455.133.63.2552,046
16955.133.64.0/2155.133.64.1 to 55.133.71.25455.133.71.2552,046
17055.133.72.0/2155.133.72.1 to 55.133.79.25455.133.79.2552,046
17155.133.80.0/2155.133.80.1 to 55.133.87.25455.133.87.2552,046
17255.133.88.0/2155.133.88.1 to 55.133.95.25455.133.95.2552,046
17355.133.96.0/2155.133.96.1 to 55.133.103.25455.133.103.2552,046
17455.133.104.0/2155.133.104.1 to 55.133.111.25455.133.111.2552,046
17555.133.112.0/2155.133.112.1 to 55.133.119.25455.133.119.2552,046
17655.133.120.0/2155.133.120.1 to 55.133.127.25455.133.127.2552,046
17755.133.128.0/2155.133.128.1 to 55.133.135.25455.133.135.2552,046
17855.133.136.0/2155.133.136.1 to 55.133.143.25455.133.143.2552,046
17955.133.144.0/2155.133.144.1 to 55.133.151.25455.133.151.2552,046
18055.133.152.0/2155.133.152.1 to 55.133.159.25455.133.159.2552,046
18155.133.160.0/2155.133.160.1 to 55.133.167.25455.133.167.2552,046
18255.133.168.0/2155.133.168.1 to 55.133.175.25455.133.175.2552,046
18355.133.176.0/2155.133.176.1 to 55.133.183.25455.133.183.2552,046
18455.133.184.0/2155.133.184.1 to 55.133.191.25455.133.191.2552,046
18555.133.192.0/2155.133.192.1 to 55.133.199.25455.133.199.2552,046
18655.133.200.0/2155.133.200.1 to 55.133.207.25455.133.207.2552,046
18755.133.208.0/2155.133.208.1 to 55.133.215.25455.133.215.2552,046
18855.133.216.0/2155.133.216.1 to 55.133.223.25455.133.223.2552,046
18955.133.224.0/2155.133.224.1 to 55.133.231.25455.133.231.2552,046
19055.133.232.0/2155.133.232.1 to 55.133.239.25455.133.239.2552,046
19155.133.240.0/2155.133.240.1 to 55.133.247.25455.133.247.2552,046
19255.133.248.0/2155.133.248.1 to 55.133.255.25455.133.255.2552,046
19355.134.0.0/2155.134.0.1 to 55.134.7.25455.134.7.2552,046
19455.134.8.0/2155.134.8.1 to 55.134.15.25455.134.15.2552,046
19555.134.16.0/2155.134.16.1 to 55.134.23.25455.134.23.2552,046
19655.134.24.0/2155.134.24.1 to 55.134.31.25455.134.31.2552,046
19755.134.32.0/2155.134.32.1 to 55.134.39.25455.134.39.2552,046
19855.134.40.0/2155.134.40.1 to 55.134.47.25455.134.47.2552,046
19955.134.48.0/2155.134.48.1 to 55.134.55.25455.134.55.2552,046
20055.134.56.0/2155.134.56.1 to 55.134.63.25455.134.63.2552,046
20155.134.64.0/2155.134.64.1 to 55.134.71.25455.134.71.2552,046
20255.134.72.0/2155.134.72.1 to 55.134.79.25455.134.79.2552,046
20355.134.80.0/2155.134.80.1 to 55.134.87.25455.134.87.2552,046
20455.134.88.0/2155.134.88.1 to 55.134.95.25455.134.95.2552,046
20555.134.96.0/2155.134.96.1 to 55.134.103.25455.134.103.2552,046
20655.134.104.0/2155.134.104.1 to 55.134.111.25455.134.111.2552,046
20755.134.112.0/2155.134.112.1 to 55.134.119.25455.134.119.2552,046
20855.134.120.0/2155.134.120.1 to 55.134.127.25455.134.127.2552,046
20955.134.128.0/2155.134.128.1 to 55.134.135.25455.134.135.2552,046
21055.134.136.0/2155.134.136.1 to 55.134.143.25455.134.143.2552,046
21155.134.144.0/2155.134.144.1 to 55.134.151.25455.134.151.2552,046
21255.134.152.0/2155.134.152.1 to 55.134.159.25455.134.159.2552,046
21355.134.160.0/2155.134.160.1 to 55.134.167.25455.134.167.2552,046
21455.134.168.0/2155.134.168.1 to 55.134.175.25455.134.175.2552,046
21555.134.176.0/2155.134.176.1 to 55.134.183.25455.134.183.2552,046
21655.134.184.0/2155.134.184.1 to 55.134.191.25455.134.191.2552,046
21755.134.192.0/2155.134.192.1 to 55.134.199.25455.134.199.2552,046
21855.134.200.0/2155.134.200.1 to 55.134.207.25455.134.207.2552,046
21955.134.208.0/2155.134.208.1 to 55.134.215.25455.134.215.2552,046
22055.134.216.0/2155.134.216.1 to 55.134.223.25455.134.223.2552,046
22155.134.224.0/2155.134.224.1 to 55.134.231.25455.134.231.2552,046
22255.134.232.0/2155.134.232.1 to 55.134.239.25455.134.239.2552,046
22355.134.240.0/2155.134.240.1 to 55.134.247.25455.134.247.2552,046
22455.134.248.0/2155.134.248.1 to 55.134.255.25455.134.255.2552,046
22555.135.0.0/2155.135.0.1 to 55.135.7.25455.135.7.2552,046
22655.135.8.0/2155.135.8.1 to 55.135.15.25455.135.15.2552,046
22755.135.16.0/2155.135.16.1 to 55.135.23.25455.135.23.2552,046
22855.135.24.0/2155.135.24.1 to 55.135.31.25455.135.31.2552,046
22955.135.32.0/2155.135.32.1 to 55.135.39.25455.135.39.2552,046
23055.135.40.0/2155.135.40.1 to 55.135.47.25455.135.47.2552,046
23155.135.48.0/2155.135.48.1 to 55.135.55.25455.135.55.2552,046
23255.135.56.0/2155.135.56.1 to 55.135.63.25455.135.63.2552,046
23355.135.64.0/2155.135.64.1 to 55.135.71.25455.135.71.2552,046
23455.135.72.0/2155.135.72.1 to 55.135.79.25455.135.79.2552,046
23555.135.80.0/2155.135.80.1 to 55.135.87.25455.135.87.2552,046
23655.135.88.0/2155.135.88.1 to 55.135.95.25455.135.95.2552,046
23755.135.96.0/2155.135.96.1 to 55.135.103.25455.135.103.2552,046
23855.135.104.0/2155.135.104.1 to 55.135.111.25455.135.111.2552,046
23955.135.112.0/2155.135.112.1 to 55.135.119.25455.135.119.2552,046
24055.135.120.0/2155.135.120.1 to 55.135.127.25455.135.127.2552,046
24155.135.128.0/2155.135.128.1 to 55.135.135.25455.135.135.2552,046
24255.135.136.0/2155.135.136.1 to 55.135.143.25455.135.143.2552,046
24355.135.144.0/2155.135.144.1 to 55.135.151.25455.135.151.2552,046
24455.135.152.0/2155.135.152.1 to 55.135.159.25455.135.159.2552,046
24555.135.160.0/2155.135.160.1 to 55.135.167.25455.135.167.2552,046
24655.135.168.0/2155.135.168.1 to 55.135.175.25455.135.175.2552,046
24755.135.176.0/2155.135.176.1 to 55.135.183.25455.135.183.2552,046
24855.135.184.0/2155.135.184.1 to 55.135.191.25455.135.191.2552,046
24955.135.192.0/2155.135.192.1 to 55.135.199.25455.135.199.2552,046
25055.135.200.0/2155.135.200.1 to 55.135.207.25455.135.207.2552,046
25155.135.208.0/2155.135.208.1 to 55.135.215.25455.135.215.2552,046
25255.135.216.0/2155.135.216.1 to 55.135.223.25455.135.223.2552,046
25355.135.224.0/2155.135.224.1 to 55.135.231.25455.135.231.2552,046
25455.135.232.0/2155.135.232.1 to 55.135.239.25455.135.239.2552,046
25555.135.240.0/2155.135.240.1 to 55.135.247.25455.135.247.2552,046
25655.135.248.0/2155.135.248.1 to 55.135.255.25455.135.255.2552,046

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.