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.

Network92.36.0.0/14
Usable hosts262,142
Subnet mask255.252.0.0
Addresses262,144
Network address
92.36.0.0
Broadcast address
92.39.255.255
First usable
92.36.0.1
Last usable
92.39.255.254
Usable hosts
262,142 (262,144 less the network and broadcast addresses)
Subnet mask
255.252.0.0
Wildcard mask
0.3.255.255 (Cisco ACLs, OSPF)
Prefix length
/14
Type
Public public
Old class
A (default /8)
As numbers
Hex 5C240000 · Integer 1545863168 to 1546125311
Reverse DNS zones
36.92.in-addr.arpa
37.92.in-addr.arpa
38.92.in-addr.arpa
39.92.in-addr.arpa
/14 is not on a 8-bit boundary, so it takes 4 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address01011100.00100100.00000000.0000000092.36.0.0
Subnet mask11111111.11111100.00000000.00000000255.252.0.0
Network01011100.00100100.00000000.0000000092.36.0.0
Broadcast01011100.00100111.11111111.1111111192.39.255.255
Split into smaller subnets/21
/15 (2)/16 (4)/17 (8)/18 (16)/19 (32)/20 (64)/21 (128)/22 (256)/23 (512)/24 (1,024)/25 (2,048)/26 (4,096)

92.36.0.0/14 makes 128 subnets of /21.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
192.36.0.0/2192.36.0.1 to 92.36.7.25492.36.7.2552,046
292.36.8.0/2192.36.8.1 to 92.36.15.25492.36.15.2552,046
392.36.16.0/2192.36.16.1 to 92.36.23.25492.36.23.2552,046
492.36.24.0/2192.36.24.1 to 92.36.31.25492.36.31.2552,046
592.36.32.0/2192.36.32.1 to 92.36.39.25492.36.39.2552,046
692.36.40.0/2192.36.40.1 to 92.36.47.25492.36.47.2552,046
792.36.48.0/2192.36.48.1 to 92.36.55.25492.36.55.2552,046
892.36.56.0/2192.36.56.1 to 92.36.63.25492.36.63.2552,046
992.36.64.0/2192.36.64.1 to 92.36.71.25492.36.71.2552,046
1092.36.72.0/2192.36.72.1 to 92.36.79.25492.36.79.2552,046
1192.36.80.0/2192.36.80.1 to 92.36.87.25492.36.87.2552,046
1292.36.88.0/2192.36.88.1 to 92.36.95.25492.36.95.2552,046
1392.36.96.0/2192.36.96.1 to 92.36.103.25492.36.103.2552,046
1492.36.104.0/2192.36.104.1 to 92.36.111.25492.36.111.2552,046
1592.36.112.0/2192.36.112.1 to 92.36.119.25492.36.119.2552,046
1692.36.120.0/2192.36.120.1 to 92.36.127.25492.36.127.2552,046
1792.36.128.0/2192.36.128.1 to 92.36.135.25492.36.135.2552,046
1892.36.136.0/2192.36.136.1 to 92.36.143.25492.36.143.2552,046
1992.36.144.0/2192.36.144.1 to 92.36.151.25492.36.151.2552,046
2092.36.152.0/2192.36.152.1 to 92.36.159.25492.36.159.2552,046
2192.36.160.0/2192.36.160.1 to 92.36.167.25492.36.167.2552,046
2292.36.168.0/2192.36.168.1 to 92.36.175.25492.36.175.2552,046
2392.36.176.0/2192.36.176.1 to 92.36.183.25492.36.183.2552,046
2492.36.184.0/2192.36.184.1 to 92.36.191.25492.36.191.2552,046
2592.36.192.0/2192.36.192.1 to 92.36.199.25492.36.199.2552,046
2692.36.200.0/2192.36.200.1 to 92.36.207.25492.36.207.2552,046
2792.36.208.0/2192.36.208.1 to 92.36.215.25492.36.215.2552,046
2892.36.216.0/2192.36.216.1 to 92.36.223.25492.36.223.2552,046
2992.36.224.0/2192.36.224.1 to 92.36.231.25492.36.231.2552,046
3092.36.232.0/2192.36.232.1 to 92.36.239.25492.36.239.2552,046
3192.36.240.0/2192.36.240.1 to 92.36.247.25492.36.247.2552,046
3292.36.248.0/2192.36.248.1 to 92.36.255.25492.36.255.2552,046
3392.37.0.0/2192.37.0.1 to 92.37.7.25492.37.7.2552,046
3492.37.8.0/2192.37.8.1 to 92.37.15.25492.37.15.2552,046
3592.37.16.0/2192.37.16.1 to 92.37.23.25492.37.23.2552,046
3692.37.24.0/2192.37.24.1 to 92.37.31.25492.37.31.2552,046
3792.37.32.0/2192.37.32.1 to 92.37.39.25492.37.39.2552,046
3892.37.40.0/2192.37.40.1 to 92.37.47.25492.37.47.2552,046
3992.37.48.0/2192.37.48.1 to 92.37.55.25492.37.55.2552,046
4092.37.56.0/2192.37.56.1 to 92.37.63.25492.37.63.2552,046
4192.37.64.0/2192.37.64.1 to 92.37.71.25492.37.71.2552,046
4292.37.72.0/2192.37.72.1 to 92.37.79.25492.37.79.2552,046
4392.37.80.0/2192.37.80.1 to 92.37.87.25492.37.87.2552,046
4492.37.88.0/2192.37.88.1 to 92.37.95.25492.37.95.2552,046
4592.37.96.0/2192.37.96.1 to 92.37.103.25492.37.103.2552,046
4692.37.104.0/2192.37.104.1 to 92.37.111.25492.37.111.2552,046
4792.37.112.0/2192.37.112.1 to 92.37.119.25492.37.119.2552,046
4892.37.120.0/2192.37.120.1 to 92.37.127.25492.37.127.2552,046
4992.37.128.0/2192.37.128.1 to 92.37.135.25492.37.135.2552,046
5092.37.136.0/2192.37.136.1 to 92.37.143.25492.37.143.2552,046
5192.37.144.0/2192.37.144.1 to 92.37.151.25492.37.151.2552,046
5292.37.152.0/2192.37.152.1 to 92.37.159.25492.37.159.2552,046
5392.37.160.0/2192.37.160.1 to 92.37.167.25492.37.167.2552,046
5492.37.168.0/2192.37.168.1 to 92.37.175.25492.37.175.2552,046
5592.37.176.0/2192.37.176.1 to 92.37.183.25492.37.183.2552,046
5692.37.184.0/2192.37.184.1 to 92.37.191.25492.37.191.2552,046
5792.37.192.0/2192.37.192.1 to 92.37.199.25492.37.199.2552,046
5892.37.200.0/2192.37.200.1 to 92.37.207.25492.37.207.2552,046
5992.37.208.0/2192.37.208.1 to 92.37.215.25492.37.215.2552,046
6092.37.216.0/2192.37.216.1 to 92.37.223.25492.37.223.2552,046
6192.37.224.0/2192.37.224.1 to 92.37.231.25492.37.231.2552,046
6292.37.232.0/2192.37.232.1 to 92.37.239.25492.37.239.2552,046
6392.37.240.0/2192.37.240.1 to 92.37.247.25492.37.247.2552,046
6492.37.248.0/2192.37.248.1 to 92.37.255.25492.37.255.2552,046
6592.38.0.0/2192.38.0.1 to 92.38.7.25492.38.7.2552,046
6692.38.8.0/2192.38.8.1 to 92.38.15.25492.38.15.2552,046
6792.38.16.0/2192.38.16.1 to 92.38.23.25492.38.23.2552,046
6892.38.24.0/2192.38.24.1 to 92.38.31.25492.38.31.2552,046
6992.38.32.0/2192.38.32.1 to 92.38.39.25492.38.39.2552,046
7092.38.40.0/2192.38.40.1 to 92.38.47.25492.38.47.2552,046
7192.38.48.0/2192.38.48.1 to 92.38.55.25492.38.55.2552,046
7292.38.56.0/2192.38.56.1 to 92.38.63.25492.38.63.2552,046
7392.38.64.0/2192.38.64.1 to 92.38.71.25492.38.71.2552,046
7492.38.72.0/2192.38.72.1 to 92.38.79.25492.38.79.2552,046
7592.38.80.0/2192.38.80.1 to 92.38.87.25492.38.87.2552,046
7692.38.88.0/2192.38.88.1 to 92.38.95.25492.38.95.2552,046
7792.38.96.0/2192.38.96.1 to 92.38.103.25492.38.103.2552,046
7892.38.104.0/2192.38.104.1 to 92.38.111.25492.38.111.2552,046
7992.38.112.0/2192.38.112.1 to 92.38.119.25492.38.119.2552,046
8092.38.120.0/2192.38.120.1 to 92.38.127.25492.38.127.2552,046
8192.38.128.0/2192.38.128.1 to 92.38.135.25492.38.135.2552,046
8292.38.136.0/2192.38.136.1 to 92.38.143.25492.38.143.2552,046
8392.38.144.0/2192.38.144.1 to 92.38.151.25492.38.151.2552,046
8492.38.152.0/2192.38.152.1 to 92.38.159.25492.38.159.2552,046
8592.38.160.0/2192.38.160.1 to 92.38.167.25492.38.167.2552,046
8692.38.168.0/2192.38.168.1 to 92.38.175.25492.38.175.2552,046
8792.38.176.0/2192.38.176.1 to 92.38.183.25492.38.183.2552,046
8892.38.184.0/2192.38.184.1 to 92.38.191.25492.38.191.2552,046
8992.38.192.0/2192.38.192.1 to 92.38.199.25492.38.199.2552,046
9092.38.200.0/2192.38.200.1 to 92.38.207.25492.38.207.2552,046
9192.38.208.0/2192.38.208.1 to 92.38.215.25492.38.215.2552,046
9292.38.216.0/2192.38.216.1 to 92.38.223.25492.38.223.2552,046
9392.38.224.0/2192.38.224.1 to 92.38.231.25492.38.231.2552,046
9492.38.232.0/2192.38.232.1 to 92.38.239.25492.38.239.2552,046
9592.38.240.0/2192.38.240.1 to 92.38.247.25492.38.247.2552,046
9692.38.248.0/2192.38.248.1 to 92.38.255.25492.38.255.2552,046
9792.39.0.0/2192.39.0.1 to 92.39.7.25492.39.7.2552,046
9892.39.8.0/2192.39.8.1 to 92.39.15.25492.39.15.2552,046
9992.39.16.0/2192.39.16.1 to 92.39.23.25492.39.23.2552,046
10092.39.24.0/2192.39.24.1 to 92.39.31.25492.39.31.2552,046
10192.39.32.0/2192.39.32.1 to 92.39.39.25492.39.39.2552,046
10292.39.40.0/2192.39.40.1 to 92.39.47.25492.39.47.2552,046
10392.39.48.0/2192.39.48.1 to 92.39.55.25492.39.55.2552,046
10492.39.56.0/2192.39.56.1 to 92.39.63.25492.39.63.2552,046
10592.39.64.0/2192.39.64.1 to 92.39.71.25492.39.71.2552,046
10692.39.72.0/2192.39.72.1 to 92.39.79.25492.39.79.2552,046
10792.39.80.0/2192.39.80.1 to 92.39.87.25492.39.87.2552,046
10892.39.88.0/2192.39.88.1 to 92.39.95.25492.39.95.2552,046
10992.39.96.0/2192.39.96.1 to 92.39.103.25492.39.103.2552,046
11092.39.104.0/2192.39.104.1 to 92.39.111.25492.39.111.2552,046
11192.39.112.0/2192.39.112.1 to 92.39.119.25492.39.119.2552,046
11292.39.120.0/2192.39.120.1 to 92.39.127.25492.39.127.2552,046
11392.39.128.0/2192.39.128.1 to 92.39.135.25492.39.135.2552,046
11492.39.136.0/2192.39.136.1 to 92.39.143.25492.39.143.2552,046
11592.39.144.0/2192.39.144.1 to 92.39.151.25492.39.151.2552,046
11692.39.152.0/2192.39.152.1 to 92.39.159.25492.39.159.2552,046
11792.39.160.0/2192.39.160.1 to 92.39.167.25492.39.167.2552,046
11892.39.168.0/2192.39.168.1 to 92.39.175.25492.39.175.2552,046
11992.39.176.0/2192.39.176.1 to 92.39.183.25492.39.183.2552,046
12092.39.184.0/2192.39.184.1 to 92.39.191.25492.39.191.2552,046
12192.39.192.0/2192.39.192.1 to 92.39.199.25492.39.199.2552,046
12292.39.200.0/2192.39.200.1 to 92.39.207.25492.39.207.2552,046
12392.39.208.0/2192.39.208.1 to 92.39.215.25492.39.215.2552,046
12492.39.216.0/2192.39.216.1 to 92.39.223.25492.39.223.2552,046
12592.39.224.0/2192.39.224.1 to 92.39.231.25492.39.231.2552,046
12692.39.232.0/2192.39.232.1 to 92.39.239.25492.39.239.2552,046
12792.39.240.0/2192.39.240.1 to 92.39.247.25492.39.247.2552,046
12892.39.248.0/2192.39.248.1 to 92.39.255.25492.39.255.2552,046

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.