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.

Network43.41.0.0/16
Usable hosts65,534
Subnet mask255.255.0.0
Addresses65,536
Network address
43.41.0.0
Broadcast address
43.41.255.255
First usable
43.41.0.1
Last usable
43.41.255.254
Usable hosts
65,534 (65,536 less the network and broadcast addresses)
Subnet mask
255.255.0.0
Wildcard mask
0.0.255.255 (Cisco ACLs, OSPF)
Prefix length
/16
Type
Public public
Old class
A (default /8)
As numbers
Hex 2B290000 · Integer 724107264 to 724172799
Reverse DNS zone
41.43.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00101011.00101001..00000000.0000000043.41.0.0
Subnet mask11111111.11111111..00000000.00000000255.255.0.0
Network00101011.00101001..00000000.0000000043.41.0.0
Broadcast00101011.00101001..11111111.1111111143.41.255.255
Split into smaller subnets/23

43.41.0.0/16 makes 128 subnets of /23.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
143.41.0.0/2343.41.0.1 to 43.41.1.25443.41.1.255510
243.41.2.0/2343.41.2.1 to 43.41.3.25443.41.3.255510
343.41.4.0/2343.41.4.1 to 43.41.5.25443.41.5.255510
443.41.6.0/2343.41.6.1 to 43.41.7.25443.41.7.255510
543.41.8.0/2343.41.8.1 to 43.41.9.25443.41.9.255510
643.41.10.0/2343.41.10.1 to 43.41.11.25443.41.11.255510
743.41.12.0/2343.41.12.1 to 43.41.13.25443.41.13.255510
843.41.14.0/2343.41.14.1 to 43.41.15.25443.41.15.255510
943.41.16.0/2343.41.16.1 to 43.41.17.25443.41.17.255510
1043.41.18.0/2343.41.18.1 to 43.41.19.25443.41.19.255510
1143.41.20.0/2343.41.20.1 to 43.41.21.25443.41.21.255510
1243.41.22.0/2343.41.22.1 to 43.41.23.25443.41.23.255510
1343.41.24.0/2343.41.24.1 to 43.41.25.25443.41.25.255510
1443.41.26.0/2343.41.26.1 to 43.41.27.25443.41.27.255510
1543.41.28.0/2343.41.28.1 to 43.41.29.25443.41.29.255510
1643.41.30.0/2343.41.30.1 to 43.41.31.25443.41.31.255510
1743.41.32.0/2343.41.32.1 to 43.41.33.25443.41.33.255510
1843.41.34.0/2343.41.34.1 to 43.41.35.25443.41.35.255510
1943.41.36.0/2343.41.36.1 to 43.41.37.25443.41.37.255510
2043.41.38.0/2343.41.38.1 to 43.41.39.25443.41.39.255510
2143.41.40.0/2343.41.40.1 to 43.41.41.25443.41.41.255510
2243.41.42.0/2343.41.42.1 to 43.41.43.25443.41.43.255510
2343.41.44.0/2343.41.44.1 to 43.41.45.25443.41.45.255510
2443.41.46.0/2343.41.46.1 to 43.41.47.25443.41.47.255510
2543.41.48.0/2343.41.48.1 to 43.41.49.25443.41.49.255510
2643.41.50.0/2343.41.50.1 to 43.41.51.25443.41.51.255510
2743.41.52.0/2343.41.52.1 to 43.41.53.25443.41.53.255510
2843.41.54.0/2343.41.54.1 to 43.41.55.25443.41.55.255510
2943.41.56.0/2343.41.56.1 to 43.41.57.25443.41.57.255510
3043.41.58.0/2343.41.58.1 to 43.41.59.25443.41.59.255510
3143.41.60.0/2343.41.60.1 to 43.41.61.25443.41.61.255510
3243.41.62.0/2343.41.62.1 to 43.41.63.25443.41.63.255510
3343.41.64.0/2343.41.64.1 to 43.41.65.25443.41.65.255510
3443.41.66.0/2343.41.66.1 to 43.41.67.25443.41.67.255510
3543.41.68.0/2343.41.68.1 to 43.41.69.25443.41.69.255510
3643.41.70.0/2343.41.70.1 to 43.41.71.25443.41.71.255510
3743.41.72.0/2343.41.72.1 to 43.41.73.25443.41.73.255510
3843.41.74.0/2343.41.74.1 to 43.41.75.25443.41.75.255510
3943.41.76.0/2343.41.76.1 to 43.41.77.25443.41.77.255510
4043.41.78.0/2343.41.78.1 to 43.41.79.25443.41.79.255510
4143.41.80.0/2343.41.80.1 to 43.41.81.25443.41.81.255510
4243.41.82.0/2343.41.82.1 to 43.41.83.25443.41.83.255510
4343.41.84.0/2343.41.84.1 to 43.41.85.25443.41.85.255510
4443.41.86.0/2343.41.86.1 to 43.41.87.25443.41.87.255510
4543.41.88.0/2343.41.88.1 to 43.41.89.25443.41.89.255510
4643.41.90.0/2343.41.90.1 to 43.41.91.25443.41.91.255510
4743.41.92.0/2343.41.92.1 to 43.41.93.25443.41.93.255510
4843.41.94.0/2343.41.94.1 to 43.41.95.25443.41.95.255510
4943.41.96.0/2343.41.96.1 to 43.41.97.25443.41.97.255510
5043.41.98.0/2343.41.98.1 to 43.41.99.25443.41.99.255510
5143.41.100.0/2343.41.100.1 to 43.41.101.25443.41.101.255510
5243.41.102.0/2343.41.102.1 to 43.41.103.25443.41.103.255510
5343.41.104.0/2343.41.104.1 to 43.41.105.25443.41.105.255510
5443.41.106.0/2343.41.106.1 to 43.41.107.25443.41.107.255510
5543.41.108.0/2343.41.108.1 to 43.41.109.25443.41.109.255510
5643.41.110.0/2343.41.110.1 to 43.41.111.25443.41.111.255510
5743.41.112.0/2343.41.112.1 to 43.41.113.25443.41.113.255510
5843.41.114.0/2343.41.114.1 to 43.41.115.25443.41.115.255510
5943.41.116.0/2343.41.116.1 to 43.41.117.25443.41.117.255510
6043.41.118.0/2343.41.118.1 to 43.41.119.25443.41.119.255510
6143.41.120.0/2343.41.120.1 to 43.41.121.25443.41.121.255510
6243.41.122.0/2343.41.122.1 to 43.41.123.25443.41.123.255510
6343.41.124.0/2343.41.124.1 to 43.41.125.25443.41.125.255510
6443.41.126.0/2343.41.126.1 to 43.41.127.25443.41.127.255510
6543.41.128.0/2343.41.128.1 to 43.41.129.25443.41.129.255510
6643.41.130.0/2343.41.130.1 to 43.41.131.25443.41.131.255510
6743.41.132.0/2343.41.132.1 to 43.41.133.25443.41.133.255510
6843.41.134.0/2343.41.134.1 to 43.41.135.25443.41.135.255510
6943.41.136.0/2343.41.136.1 to 43.41.137.25443.41.137.255510
7043.41.138.0/2343.41.138.1 to 43.41.139.25443.41.139.255510
7143.41.140.0/2343.41.140.1 to 43.41.141.25443.41.141.255510
7243.41.142.0/2343.41.142.1 to 43.41.143.25443.41.143.255510
7343.41.144.0/2343.41.144.1 to 43.41.145.25443.41.145.255510
7443.41.146.0/2343.41.146.1 to 43.41.147.25443.41.147.255510
7543.41.148.0/2343.41.148.1 to 43.41.149.25443.41.149.255510
7643.41.150.0/2343.41.150.1 to 43.41.151.25443.41.151.255510
7743.41.152.0/2343.41.152.1 to 43.41.153.25443.41.153.255510
7843.41.154.0/2343.41.154.1 to 43.41.155.25443.41.155.255510
7943.41.156.0/2343.41.156.1 to 43.41.157.25443.41.157.255510
8043.41.158.0/2343.41.158.1 to 43.41.159.25443.41.159.255510
8143.41.160.0/2343.41.160.1 to 43.41.161.25443.41.161.255510
8243.41.162.0/2343.41.162.1 to 43.41.163.25443.41.163.255510
8343.41.164.0/2343.41.164.1 to 43.41.165.25443.41.165.255510
8443.41.166.0/2343.41.166.1 to 43.41.167.25443.41.167.255510
8543.41.168.0/2343.41.168.1 to 43.41.169.25443.41.169.255510
8643.41.170.0/2343.41.170.1 to 43.41.171.25443.41.171.255510
8743.41.172.0/2343.41.172.1 to 43.41.173.25443.41.173.255510
8843.41.174.0/2343.41.174.1 to 43.41.175.25443.41.175.255510
8943.41.176.0/2343.41.176.1 to 43.41.177.25443.41.177.255510
9043.41.178.0/2343.41.178.1 to 43.41.179.25443.41.179.255510
9143.41.180.0/2343.41.180.1 to 43.41.181.25443.41.181.255510
9243.41.182.0/2343.41.182.1 to 43.41.183.25443.41.183.255510
9343.41.184.0/2343.41.184.1 to 43.41.185.25443.41.185.255510
9443.41.186.0/2343.41.186.1 to 43.41.187.25443.41.187.255510
9543.41.188.0/2343.41.188.1 to 43.41.189.25443.41.189.255510
9643.41.190.0/2343.41.190.1 to 43.41.191.25443.41.191.255510
9743.41.192.0/2343.41.192.1 to 43.41.193.25443.41.193.255510
9843.41.194.0/2343.41.194.1 to 43.41.195.25443.41.195.255510
9943.41.196.0/2343.41.196.1 to 43.41.197.25443.41.197.255510
10043.41.198.0/2343.41.198.1 to 43.41.199.25443.41.199.255510
10143.41.200.0/2343.41.200.1 to 43.41.201.25443.41.201.255510
10243.41.202.0/2343.41.202.1 to 43.41.203.25443.41.203.255510
10343.41.204.0/2343.41.204.1 to 43.41.205.25443.41.205.255510
10443.41.206.0/2343.41.206.1 to 43.41.207.25443.41.207.255510
10543.41.208.0/2343.41.208.1 to 43.41.209.25443.41.209.255510
10643.41.210.0/2343.41.210.1 to 43.41.211.25443.41.211.255510
10743.41.212.0/2343.41.212.1 to 43.41.213.25443.41.213.255510
10843.41.214.0/2343.41.214.1 to 43.41.215.25443.41.215.255510
10943.41.216.0/2343.41.216.1 to 43.41.217.25443.41.217.255510
11043.41.218.0/2343.41.218.1 to 43.41.219.25443.41.219.255510
11143.41.220.0/2343.41.220.1 to 43.41.221.25443.41.221.255510
11243.41.222.0/2343.41.222.1 to 43.41.223.25443.41.223.255510
11343.41.224.0/2343.41.224.1 to 43.41.225.25443.41.225.255510
11443.41.226.0/2343.41.226.1 to 43.41.227.25443.41.227.255510
11543.41.228.0/2343.41.228.1 to 43.41.229.25443.41.229.255510
11643.41.230.0/2343.41.230.1 to 43.41.231.25443.41.231.255510
11743.41.232.0/2343.41.232.1 to 43.41.233.25443.41.233.255510
11843.41.234.0/2343.41.234.1 to 43.41.235.25443.41.235.255510
11943.41.236.0/2343.41.236.1 to 43.41.237.25443.41.237.255510
12043.41.238.0/2343.41.238.1 to 43.41.239.25443.41.239.255510
12143.41.240.0/2343.41.240.1 to 43.41.241.25443.41.241.255510
12243.41.242.0/2343.41.242.1 to 43.41.243.25443.41.243.255510
12343.41.244.0/2343.41.244.1 to 43.41.245.25443.41.245.255510
12443.41.246.0/2343.41.246.1 to 43.41.247.25443.41.247.255510
12543.41.248.0/2343.41.248.1 to 43.41.249.25443.41.249.255510
12643.41.250.0/2343.41.250.1 to 43.41.251.25443.41.251.255510
12743.41.252.0/2343.41.252.1 to 43.41.253.25443.41.253.255510
12843.41.254.0/2343.41.254.1 to 43.41.255.25443.41.255.255510

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