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.

Network41.232.0.0/14
Usable hosts262,142
Subnet mask255.252.0.0
Addresses262,144
Network address
41.232.0.0
Broadcast address
41.235.255.255
First usable
41.232.0.1
Last usable
41.235.255.254
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 29E80000 · Integer 703070208 to 703332351
Reverse DNS zones
232.41.in-addr.arpa
233.41.in-addr.arpa
234.41.in-addr.arpa
235.41.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
Address00101001.11101000.00000000.0000000041.232.0.0
Subnet mask11111111.11111100.00000000.00000000255.252.0.0
Network00101001.11101000.00000000.0000000041.232.0.0
Broadcast00101001.11101011.11111111.1111111141.235.255.255
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)

41.232.0.0/14 makes 128 subnets of /21.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
141.232.0.0/2141.232.0.1 to 41.232.7.25441.232.7.2552,046
241.232.8.0/2141.232.8.1 to 41.232.15.25441.232.15.2552,046
341.232.16.0/2141.232.16.1 to 41.232.23.25441.232.23.2552,046
441.232.24.0/2141.232.24.1 to 41.232.31.25441.232.31.2552,046
541.232.32.0/2141.232.32.1 to 41.232.39.25441.232.39.2552,046
641.232.40.0/2141.232.40.1 to 41.232.47.25441.232.47.2552,046
741.232.48.0/2141.232.48.1 to 41.232.55.25441.232.55.2552,046
841.232.56.0/2141.232.56.1 to 41.232.63.25441.232.63.2552,046
941.232.64.0/2141.232.64.1 to 41.232.71.25441.232.71.2552,046
1041.232.72.0/2141.232.72.1 to 41.232.79.25441.232.79.2552,046
1141.232.80.0/2141.232.80.1 to 41.232.87.25441.232.87.2552,046
1241.232.88.0/2141.232.88.1 to 41.232.95.25441.232.95.2552,046
1341.232.96.0/2141.232.96.1 to 41.232.103.25441.232.103.2552,046
1441.232.104.0/2141.232.104.1 to 41.232.111.25441.232.111.2552,046
1541.232.112.0/2141.232.112.1 to 41.232.119.25441.232.119.2552,046
1641.232.120.0/2141.232.120.1 to 41.232.127.25441.232.127.2552,046
1741.232.128.0/2141.232.128.1 to 41.232.135.25441.232.135.2552,046
1841.232.136.0/2141.232.136.1 to 41.232.143.25441.232.143.2552,046
1941.232.144.0/2141.232.144.1 to 41.232.151.25441.232.151.2552,046
2041.232.152.0/2141.232.152.1 to 41.232.159.25441.232.159.2552,046
2141.232.160.0/2141.232.160.1 to 41.232.167.25441.232.167.2552,046
2241.232.168.0/2141.232.168.1 to 41.232.175.25441.232.175.2552,046
2341.232.176.0/2141.232.176.1 to 41.232.183.25441.232.183.2552,046
2441.232.184.0/2141.232.184.1 to 41.232.191.25441.232.191.2552,046
2541.232.192.0/2141.232.192.1 to 41.232.199.25441.232.199.2552,046
2641.232.200.0/2141.232.200.1 to 41.232.207.25441.232.207.2552,046
2741.232.208.0/2141.232.208.1 to 41.232.215.25441.232.215.2552,046
2841.232.216.0/2141.232.216.1 to 41.232.223.25441.232.223.2552,046
2941.232.224.0/2141.232.224.1 to 41.232.231.25441.232.231.2552,046
3041.232.232.0/2141.232.232.1 to 41.232.239.25441.232.239.2552,046
3141.232.240.0/2141.232.240.1 to 41.232.247.25441.232.247.2552,046
3241.232.248.0/2141.232.248.1 to 41.232.255.25441.232.255.2552,046
3341.233.0.0/2141.233.0.1 to 41.233.7.25441.233.7.2552,046
3441.233.8.0/2141.233.8.1 to 41.233.15.25441.233.15.2552,046
3541.233.16.0/2141.233.16.1 to 41.233.23.25441.233.23.2552,046
3641.233.24.0/2141.233.24.1 to 41.233.31.25441.233.31.2552,046
3741.233.32.0/2141.233.32.1 to 41.233.39.25441.233.39.2552,046
3841.233.40.0/2141.233.40.1 to 41.233.47.25441.233.47.2552,046
3941.233.48.0/2141.233.48.1 to 41.233.55.25441.233.55.2552,046
4041.233.56.0/2141.233.56.1 to 41.233.63.25441.233.63.2552,046
4141.233.64.0/2141.233.64.1 to 41.233.71.25441.233.71.2552,046
4241.233.72.0/2141.233.72.1 to 41.233.79.25441.233.79.2552,046
4341.233.80.0/2141.233.80.1 to 41.233.87.25441.233.87.2552,046
4441.233.88.0/2141.233.88.1 to 41.233.95.25441.233.95.2552,046
4541.233.96.0/2141.233.96.1 to 41.233.103.25441.233.103.2552,046
4641.233.104.0/2141.233.104.1 to 41.233.111.25441.233.111.2552,046
4741.233.112.0/2141.233.112.1 to 41.233.119.25441.233.119.2552,046
4841.233.120.0/2141.233.120.1 to 41.233.127.25441.233.127.2552,046
4941.233.128.0/2141.233.128.1 to 41.233.135.25441.233.135.2552,046
5041.233.136.0/2141.233.136.1 to 41.233.143.25441.233.143.2552,046
5141.233.144.0/2141.233.144.1 to 41.233.151.25441.233.151.2552,046
5241.233.152.0/2141.233.152.1 to 41.233.159.25441.233.159.2552,046
5341.233.160.0/2141.233.160.1 to 41.233.167.25441.233.167.2552,046
5441.233.168.0/2141.233.168.1 to 41.233.175.25441.233.175.2552,046
5541.233.176.0/2141.233.176.1 to 41.233.183.25441.233.183.2552,046
5641.233.184.0/2141.233.184.1 to 41.233.191.25441.233.191.2552,046
5741.233.192.0/2141.233.192.1 to 41.233.199.25441.233.199.2552,046
5841.233.200.0/2141.233.200.1 to 41.233.207.25441.233.207.2552,046
5941.233.208.0/2141.233.208.1 to 41.233.215.25441.233.215.2552,046
6041.233.216.0/2141.233.216.1 to 41.233.223.25441.233.223.2552,046
6141.233.224.0/2141.233.224.1 to 41.233.231.25441.233.231.2552,046
6241.233.232.0/2141.233.232.1 to 41.233.239.25441.233.239.2552,046
6341.233.240.0/2141.233.240.1 to 41.233.247.25441.233.247.2552,046
6441.233.248.0/2141.233.248.1 to 41.233.255.25441.233.255.2552,046
6541.234.0.0/2141.234.0.1 to 41.234.7.25441.234.7.2552,046
6641.234.8.0/2141.234.8.1 to 41.234.15.25441.234.15.2552,046
6741.234.16.0/2141.234.16.1 to 41.234.23.25441.234.23.2552,046
6841.234.24.0/2141.234.24.1 to 41.234.31.25441.234.31.2552,046
6941.234.32.0/2141.234.32.1 to 41.234.39.25441.234.39.2552,046
7041.234.40.0/2141.234.40.1 to 41.234.47.25441.234.47.2552,046
7141.234.48.0/2141.234.48.1 to 41.234.55.25441.234.55.2552,046
7241.234.56.0/2141.234.56.1 to 41.234.63.25441.234.63.2552,046
7341.234.64.0/2141.234.64.1 to 41.234.71.25441.234.71.2552,046
7441.234.72.0/2141.234.72.1 to 41.234.79.25441.234.79.2552,046
7541.234.80.0/2141.234.80.1 to 41.234.87.25441.234.87.2552,046
7641.234.88.0/2141.234.88.1 to 41.234.95.25441.234.95.2552,046
7741.234.96.0/2141.234.96.1 to 41.234.103.25441.234.103.2552,046
7841.234.104.0/2141.234.104.1 to 41.234.111.25441.234.111.2552,046
7941.234.112.0/2141.234.112.1 to 41.234.119.25441.234.119.2552,046
8041.234.120.0/2141.234.120.1 to 41.234.127.25441.234.127.2552,046
8141.234.128.0/2141.234.128.1 to 41.234.135.25441.234.135.2552,046
8241.234.136.0/2141.234.136.1 to 41.234.143.25441.234.143.2552,046
8341.234.144.0/2141.234.144.1 to 41.234.151.25441.234.151.2552,046
8441.234.152.0/2141.234.152.1 to 41.234.159.25441.234.159.2552,046
8541.234.160.0/2141.234.160.1 to 41.234.167.25441.234.167.2552,046
8641.234.168.0/2141.234.168.1 to 41.234.175.25441.234.175.2552,046
8741.234.176.0/2141.234.176.1 to 41.234.183.25441.234.183.2552,046
8841.234.184.0/2141.234.184.1 to 41.234.191.25441.234.191.2552,046
8941.234.192.0/2141.234.192.1 to 41.234.199.25441.234.199.2552,046
9041.234.200.0/2141.234.200.1 to 41.234.207.25441.234.207.2552,046
9141.234.208.0/2141.234.208.1 to 41.234.215.25441.234.215.2552,046
9241.234.216.0/2141.234.216.1 to 41.234.223.25441.234.223.2552,046
9341.234.224.0/2141.234.224.1 to 41.234.231.25441.234.231.2552,046
9441.234.232.0/2141.234.232.1 to 41.234.239.25441.234.239.2552,046
9541.234.240.0/2141.234.240.1 to 41.234.247.25441.234.247.2552,046
9641.234.248.0/2141.234.248.1 to 41.234.255.25441.234.255.2552,046
9741.235.0.0/2141.235.0.1 to 41.235.7.25441.235.7.2552,046
9841.235.8.0/2141.235.8.1 to 41.235.15.25441.235.15.2552,046
9941.235.16.0/2141.235.16.1 to 41.235.23.25441.235.23.2552,046
10041.235.24.0/2141.235.24.1 to 41.235.31.25441.235.31.2552,046
10141.235.32.0/2141.235.32.1 to 41.235.39.25441.235.39.2552,046
10241.235.40.0/2141.235.40.1 to 41.235.47.25441.235.47.2552,046
10341.235.48.0/2141.235.48.1 to 41.235.55.25441.235.55.2552,046
10441.235.56.0/2141.235.56.1 to 41.235.63.25441.235.63.2552,046
10541.235.64.0/2141.235.64.1 to 41.235.71.25441.235.71.2552,046
10641.235.72.0/2141.235.72.1 to 41.235.79.25441.235.79.2552,046
10741.235.80.0/2141.235.80.1 to 41.235.87.25441.235.87.2552,046
10841.235.88.0/2141.235.88.1 to 41.235.95.25441.235.95.2552,046
10941.235.96.0/2141.235.96.1 to 41.235.103.25441.235.103.2552,046
11041.235.104.0/2141.235.104.1 to 41.235.111.25441.235.111.2552,046
11141.235.112.0/2141.235.112.1 to 41.235.119.25441.235.119.2552,046
11241.235.120.0/2141.235.120.1 to 41.235.127.25441.235.127.2552,046
11341.235.128.0/2141.235.128.1 to 41.235.135.25441.235.135.2552,046
11441.235.136.0/2141.235.136.1 to 41.235.143.25441.235.143.2552,046
11541.235.144.0/2141.235.144.1 to 41.235.151.25441.235.151.2552,046
11641.235.152.0/2141.235.152.1 to 41.235.159.25441.235.159.2552,046
11741.235.160.0/2141.235.160.1 to 41.235.167.25441.235.167.2552,046
11841.235.168.0/2141.235.168.1 to 41.235.175.25441.235.175.2552,046
11941.235.176.0/2141.235.176.1 to 41.235.183.25441.235.183.2552,046
12041.235.184.0/2141.235.184.1 to 41.235.191.25441.235.191.2552,046
12141.235.192.0/2141.235.192.1 to 41.235.199.25441.235.199.2552,046
12241.235.200.0/2141.235.200.1 to 41.235.207.25441.235.207.2552,046
12341.235.208.0/2141.235.208.1 to 41.235.215.25441.235.215.2552,046
12441.235.216.0/2141.235.216.1 to 41.235.223.25441.235.223.2552,046
12541.235.224.0/2141.235.224.1 to 41.235.231.25441.235.231.2552,046
12641.235.232.0/2141.235.232.1 to 41.235.239.25441.235.239.2552,046
12741.235.240.0/2141.235.240.1 to 41.235.247.25441.235.247.2552,046
12841.235.248.0/2141.235.248.1 to 41.235.255.25441.235.255.2552,046

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.