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.

Network156.2.0.0/16
Usable hosts65,534
Subnet mask255.255.0.0
Addresses65,536
Network address
156.2.0.0
Broadcast address
156.2.255.255
First usable
156.2.0.1
Last usable
156.2.255.254
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
B (default /16)
As numbers
Hex 9C020000 · Integer 2617376768 to 2617442303
Reverse DNS zone
2.156.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10011100.00000010..00000000.00000000156.2.0.0
Subnet mask11111111.11111111..00000000.00000000255.255.0.0
Network10011100.00000010..00000000.00000000156.2.0.0
Broadcast10011100.00000010..11111111.11111111156.2.255.255
Split into smaller subnets/23

156.2.0.0/16 makes 128 subnets of /23.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1156.2.0.0/23156.2.0.1 to 156.2.1.254156.2.1.255510
2156.2.2.0/23156.2.2.1 to 156.2.3.254156.2.3.255510
3156.2.4.0/23156.2.4.1 to 156.2.5.254156.2.5.255510
4156.2.6.0/23156.2.6.1 to 156.2.7.254156.2.7.255510
5156.2.8.0/23156.2.8.1 to 156.2.9.254156.2.9.255510
6156.2.10.0/23156.2.10.1 to 156.2.11.254156.2.11.255510
7156.2.12.0/23156.2.12.1 to 156.2.13.254156.2.13.255510
8156.2.14.0/23156.2.14.1 to 156.2.15.254156.2.15.255510
9156.2.16.0/23156.2.16.1 to 156.2.17.254156.2.17.255510
10156.2.18.0/23156.2.18.1 to 156.2.19.254156.2.19.255510
11156.2.20.0/23156.2.20.1 to 156.2.21.254156.2.21.255510
12156.2.22.0/23156.2.22.1 to 156.2.23.254156.2.23.255510
13156.2.24.0/23156.2.24.1 to 156.2.25.254156.2.25.255510
14156.2.26.0/23156.2.26.1 to 156.2.27.254156.2.27.255510
15156.2.28.0/23156.2.28.1 to 156.2.29.254156.2.29.255510
16156.2.30.0/23156.2.30.1 to 156.2.31.254156.2.31.255510
17156.2.32.0/23156.2.32.1 to 156.2.33.254156.2.33.255510
18156.2.34.0/23156.2.34.1 to 156.2.35.254156.2.35.255510
19156.2.36.0/23156.2.36.1 to 156.2.37.254156.2.37.255510
20156.2.38.0/23156.2.38.1 to 156.2.39.254156.2.39.255510
21156.2.40.0/23156.2.40.1 to 156.2.41.254156.2.41.255510
22156.2.42.0/23156.2.42.1 to 156.2.43.254156.2.43.255510
23156.2.44.0/23156.2.44.1 to 156.2.45.254156.2.45.255510
24156.2.46.0/23156.2.46.1 to 156.2.47.254156.2.47.255510
25156.2.48.0/23156.2.48.1 to 156.2.49.254156.2.49.255510
26156.2.50.0/23156.2.50.1 to 156.2.51.254156.2.51.255510
27156.2.52.0/23156.2.52.1 to 156.2.53.254156.2.53.255510
28156.2.54.0/23156.2.54.1 to 156.2.55.254156.2.55.255510
29156.2.56.0/23156.2.56.1 to 156.2.57.254156.2.57.255510
30156.2.58.0/23156.2.58.1 to 156.2.59.254156.2.59.255510
31156.2.60.0/23156.2.60.1 to 156.2.61.254156.2.61.255510
32156.2.62.0/23156.2.62.1 to 156.2.63.254156.2.63.255510
33156.2.64.0/23156.2.64.1 to 156.2.65.254156.2.65.255510
34156.2.66.0/23156.2.66.1 to 156.2.67.254156.2.67.255510
35156.2.68.0/23156.2.68.1 to 156.2.69.254156.2.69.255510
36156.2.70.0/23156.2.70.1 to 156.2.71.254156.2.71.255510
37156.2.72.0/23156.2.72.1 to 156.2.73.254156.2.73.255510
38156.2.74.0/23156.2.74.1 to 156.2.75.254156.2.75.255510
39156.2.76.0/23156.2.76.1 to 156.2.77.254156.2.77.255510
40156.2.78.0/23156.2.78.1 to 156.2.79.254156.2.79.255510
41156.2.80.0/23156.2.80.1 to 156.2.81.254156.2.81.255510
42156.2.82.0/23156.2.82.1 to 156.2.83.254156.2.83.255510
43156.2.84.0/23156.2.84.1 to 156.2.85.254156.2.85.255510
44156.2.86.0/23156.2.86.1 to 156.2.87.254156.2.87.255510
45156.2.88.0/23156.2.88.1 to 156.2.89.254156.2.89.255510
46156.2.90.0/23156.2.90.1 to 156.2.91.254156.2.91.255510
47156.2.92.0/23156.2.92.1 to 156.2.93.254156.2.93.255510
48156.2.94.0/23156.2.94.1 to 156.2.95.254156.2.95.255510
49156.2.96.0/23156.2.96.1 to 156.2.97.254156.2.97.255510
50156.2.98.0/23156.2.98.1 to 156.2.99.254156.2.99.255510
51156.2.100.0/23156.2.100.1 to 156.2.101.254156.2.101.255510
52156.2.102.0/23156.2.102.1 to 156.2.103.254156.2.103.255510
53156.2.104.0/23156.2.104.1 to 156.2.105.254156.2.105.255510
54156.2.106.0/23156.2.106.1 to 156.2.107.254156.2.107.255510
55156.2.108.0/23156.2.108.1 to 156.2.109.254156.2.109.255510
56156.2.110.0/23156.2.110.1 to 156.2.111.254156.2.111.255510
57156.2.112.0/23156.2.112.1 to 156.2.113.254156.2.113.255510
58156.2.114.0/23156.2.114.1 to 156.2.115.254156.2.115.255510
59156.2.116.0/23156.2.116.1 to 156.2.117.254156.2.117.255510
60156.2.118.0/23156.2.118.1 to 156.2.119.254156.2.119.255510
61156.2.120.0/23156.2.120.1 to 156.2.121.254156.2.121.255510
62156.2.122.0/23156.2.122.1 to 156.2.123.254156.2.123.255510
63156.2.124.0/23156.2.124.1 to 156.2.125.254156.2.125.255510
64156.2.126.0/23156.2.126.1 to 156.2.127.254156.2.127.255510
65156.2.128.0/23156.2.128.1 to 156.2.129.254156.2.129.255510
66156.2.130.0/23156.2.130.1 to 156.2.131.254156.2.131.255510
67156.2.132.0/23156.2.132.1 to 156.2.133.254156.2.133.255510
68156.2.134.0/23156.2.134.1 to 156.2.135.254156.2.135.255510
69156.2.136.0/23156.2.136.1 to 156.2.137.254156.2.137.255510
70156.2.138.0/23156.2.138.1 to 156.2.139.254156.2.139.255510
71156.2.140.0/23156.2.140.1 to 156.2.141.254156.2.141.255510
72156.2.142.0/23156.2.142.1 to 156.2.143.254156.2.143.255510
73156.2.144.0/23156.2.144.1 to 156.2.145.254156.2.145.255510
74156.2.146.0/23156.2.146.1 to 156.2.147.254156.2.147.255510
75156.2.148.0/23156.2.148.1 to 156.2.149.254156.2.149.255510
76156.2.150.0/23156.2.150.1 to 156.2.151.254156.2.151.255510
77156.2.152.0/23156.2.152.1 to 156.2.153.254156.2.153.255510
78156.2.154.0/23156.2.154.1 to 156.2.155.254156.2.155.255510
79156.2.156.0/23156.2.156.1 to 156.2.157.254156.2.157.255510
80156.2.158.0/23156.2.158.1 to 156.2.159.254156.2.159.255510
81156.2.160.0/23156.2.160.1 to 156.2.161.254156.2.161.255510
82156.2.162.0/23156.2.162.1 to 156.2.163.254156.2.163.255510
83156.2.164.0/23156.2.164.1 to 156.2.165.254156.2.165.255510
84156.2.166.0/23156.2.166.1 to 156.2.167.254156.2.167.255510
85156.2.168.0/23156.2.168.1 to 156.2.169.254156.2.169.255510
86156.2.170.0/23156.2.170.1 to 156.2.171.254156.2.171.255510
87156.2.172.0/23156.2.172.1 to 156.2.173.254156.2.173.255510
88156.2.174.0/23156.2.174.1 to 156.2.175.254156.2.175.255510
89156.2.176.0/23156.2.176.1 to 156.2.177.254156.2.177.255510
90156.2.178.0/23156.2.178.1 to 156.2.179.254156.2.179.255510
91156.2.180.0/23156.2.180.1 to 156.2.181.254156.2.181.255510
92156.2.182.0/23156.2.182.1 to 156.2.183.254156.2.183.255510
93156.2.184.0/23156.2.184.1 to 156.2.185.254156.2.185.255510
94156.2.186.0/23156.2.186.1 to 156.2.187.254156.2.187.255510
95156.2.188.0/23156.2.188.1 to 156.2.189.254156.2.189.255510
96156.2.190.0/23156.2.190.1 to 156.2.191.254156.2.191.255510
97156.2.192.0/23156.2.192.1 to 156.2.193.254156.2.193.255510
98156.2.194.0/23156.2.194.1 to 156.2.195.254156.2.195.255510
99156.2.196.0/23156.2.196.1 to 156.2.197.254156.2.197.255510
100156.2.198.0/23156.2.198.1 to 156.2.199.254156.2.199.255510
101156.2.200.0/23156.2.200.1 to 156.2.201.254156.2.201.255510
102156.2.202.0/23156.2.202.1 to 156.2.203.254156.2.203.255510
103156.2.204.0/23156.2.204.1 to 156.2.205.254156.2.205.255510
104156.2.206.0/23156.2.206.1 to 156.2.207.254156.2.207.255510
105156.2.208.0/23156.2.208.1 to 156.2.209.254156.2.209.255510
106156.2.210.0/23156.2.210.1 to 156.2.211.254156.2.211.255510
107156.2.212.0/23156.2.212.1 to 156.2.213.254156.2.213.255510
108156.2.214.0/23156.2.214.1 to 156.2.215.254156.2.215.255510
109156.2.216.0/23156.2.216.1 to 156.2.217.254156.2.217.255510
110156.2.218.0/23156.2.218.1 to 156.2.219.254156.2.219.255510
111156.2.220.0/23156.2.220.1 to 156.2.221.254156.2.221.255510
112156.2.222.0/23156.2.222.1 to 156.2.223.254156.2.223.255510
113156.2.224.0/23156.2.224.1 to 156.2.225.254156.2.225.255510
114156.2.226.0/23156.2.226.1 to 156.2.227.254156.2.227.255510
115156.2.228.0/23156.2.228.1 to 156.2.229.254156.2.229.255510
116156.2.230.0/23156.2.230.1 to 156.2.231.254156.2.231.255510
117156.2.232.0/23156.2.232.1 to 156.2.233.254156.2.233.255510
118156.2.234.0/23156.2.234.1 to 156.2.235.254156.2.235.255510
119156.2.236.0/23156.2.236.1 to 156.2.237.254156.2.237.255510
120156.2.238.0/23156.2.238.1 to 156.2.239.254156.2.239.255510
121156.2.240.0/23156.2.240.1 to 156.2.241.254156.2.241.255510
122156.2.242.0/23156.2.242.1 to 156.2.243.254156.2.243.255510
123156.2.244.0/23156.2.244.1 to 156.2.245.254156.2.245.255510
124156.2.246.0/23156.2.246.1 to 156.2.247.254156.2.247.255510
125156.2.248.0/23156.2.248.1 to 156.2.249.254156.2.249.255510
126156.2.250.0/23156.2.250.1 to 156.2.251.254156.2.251.255510
127156.2.252.0/23156.2.252.1 to 156.2.253.254156.2.253.255510
128156.2.254.0/23156.2.254.1 to 156.2.255.254156.2.255.255510

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