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.

Network167.149.0.0/16
Usable hosts65,534
Subnet mask255.255.0.0
Addresses65,536
Network address
167.149.0.0
Broadcast address
167.149.255.255
First usable
167.149.0.1
Last usable
167.149.255.254
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 A7950000 · Integer 2811559936 to 2811625471
Reverse DNS zone
149.167.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10100111.10010101..00000000.00000000167.149.0.0
Subnet mask11111111.11111111..00000000.00000000255.255.0.0
Network10100111.10010101..00000000.00000000167.149.0.0
Broadcast10100111.10010101..11111111.11111111167.149.255.255
Split into smaller subnets/23
/17 (2)/18 (4)/19 (8)/20 (16)/21 (32)/22 (64)/23 (128)/24 (256)/25 (512)/26 (1,024)/27 (2,048)/28 (4,096)

167.149.0.0/16 makes 128 subnets of /23.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1167.149.0.0/23167.149.0.1 to 167.149.1.254167.149.1.255510
2167.149.2.0/23167.149.2.1 to 167.149.3.254167.149.3.255510
3167.149.4.0/23167.149.4.1 to 167.149.5.254167.149.5.255510
4167.149.6.0/23167.149.6.1 to 167.149.7.254167.149.7.255510
5167.149.8.0/23167.149.8.1 to 167.149.9.254167.149.9.255510
6167.149.10.0/23167.149.10.1 to 167.149.11.254167.149.11.255510
7167.149.12.0/23167.149.12.1 to 167.149.13.254167.149.13.255510
8167.149.14.0/23167.149.14.1 to 167.149.15.254167.149.15.255510
9167.149.16.0/23167.149.16.1 to 167.149.17.254167.149.17.255510
10167.149.18.0/23167.149.18.1 to 167.149.19.254167.149.19.255510
11167.149.20.0/23167.149.20.1 to 167.149.21.254167.149.21.255510
12167.149.22.0/23167.149.22.1 to 167.149.23.254167.149.23.255510
13167.149.24.0/23167.149.24.1 to 167.149.25.254167.149.25.255510
14167.149.26.0/23167.149.26.1 to 167.149.27.254167.149.27.255510
15167.149.28.0/23167.149.28.1 to 167.149.29.254167.149.29.255510
16167.149.30.0/23167.149.30.1 to 167.149.31.254167.149.31.255510
17167.149.32.0/23167.149.32.1 to 167.149.33.254167.149.33.255510
18167.149.34.0/23167.149.34.1 to 167.149.35.254167.149.35.255510
19167.149.36.0/23167.149.36.1 to 167.149.37.254167.149.37.255510
20167.149.38.0/23167.149.38.1 to 167.149.39.254167.149.39.255510
21167.149.40.0/23167.149.40.1 to 167.149.41.254167.149.41.255510
22167.149.42.0/23167.149.42.1 to 167.149.43.254167.149.43.255510
23167.149.44.0/23167.149.44.1 to 167.149.45.254167.149.45.255510
24167.149.46.0/23167.149.46.1 to 167.149.47.254167.149.47.255510
25167.149.48.0/23167.149.48.1 to 167.149.49.254167.149.49.255510
26167.149.50.0/23167.149.50.1 to 167.149.51.254167.149.51.255510
27167.149.52.0/23167.149.52.1 to 167.149.53.254167.149.53.255510
28167.149.54.0/23167.149.54.1 to 167.149.55.254167.149.55.255510
29167.149.56.0/23167.149.56.1 to 167.149.57.254167.149.57.255510
30167.149.58.0/23167.149.58.1 to 167.149.59.254167.149.59.255510
31167.149.60.0/23167.149.60.1 to 167.149.61.254167.149.61.255510
32167.149.62.0/23167.149.62.1 to 167.149.63.254167.149.63.255510
33167.149.64.0/23167.149.64.1 to 167.149.65.254167.149.65.255510
34167.149.66.0/23167.149.66.1 to 167.149.67.254167.149.67.255510
35167.149.68.0/23167.149.68.1 to 167.149.69.254167.149.69.255510
36167.149.70.0/23167.149.70.1 to 167.149.71.254167.149.71.255510
37167.149.72.0/23167.149.72.1 to 167.149.73.254167.149.73.255510
38167.149.74.0/23167.149.74.1 to 167.149.75.254167.149.75.255510
39167.149.76.0/23167.149.76.1 to 167.149.77.254167.149.77.255510
40167.149.78.0/23167.149.78.1 to 167.149.79.254167.149.79.255510
41167.149.80.0/23167.149.80.1 to 167.149.81.254167.149.81.255510
42167.149.82.0/23167.149.82.1 to 167.149.83.254167.149.83.255510
43167.149.84.0/23167.149.84.1 to 167.149.85.254167.149.85.255510
44167.149.86.0/23167.149.86.1 to 167.149.87.254167.149.87.255510
45167.149.88.0/23167.149.88.1 to 167.149.89.254167.149.89.255510
46167.149.90.0/23167.149.90.1 to 167.149.91.254167.149.91.255510
47167.149.92.0/23167.149.92.1 to 167.149.93.254167.149.93.255510
48167.149.94.0/23167.149.94.1 to 167.149.95.254167.149.95.255510
49167.149.96.0/23167.149.96.1 to 167.149.97.254167.149.97.255510
50167.149.98.0/23167.149.98.1 to 167.149.99.254167.149.99.255510
51167.149.100.0/23167.149.100.1 to 167.149.101.254167.149.101.255510
52167.149.102.0/23167.149.102.1 to 167.149.103.254167.149.103.255510
53167.149.104.0/23167.149.104.1 to 167.149.105.254167.149.105.255510
54167.149.106.0/23167.149.106.1 to 167.149.107.254167.149.107.255510
55167.149.108.0/23167.149.108.1 to 167.149.109.254167.149.109.255510
56167.149.110.0/23167.149.110.1 to 167.149.111.254167.149.111.255510
57167.149.112.0/23167.149.112.1 to 167.149.113.254167.149.113.255510
58167.149.114.0/23167.149.114.1 to 167.149.115.254167.149.115.255510
59167.149.116.0/23167.149.116.1 to 167.149.117.254167.149.117.255510
60167.149.118.0/23167.149.118.1 to 167.149.119.254167.149.119.255510
61167.149.120.0/23167.149.120.1 to 167.149.121.254167.149.121.255510
62167.149.122.0/23167.149.122.1 to 167.149.123.254167.149.123.255510
63167.149.124.0/23167.149.124.1 to 167.149.125.254167.149.125.255510
64167.149.126.0/23167.149.126.1 to 167.149.127.254167.149.127.255510
65167.149.128.0/23167.149.128.1 to 167.149.129.254167.149.129.255510
66167.149.130.0/23167.149.130.1 to 167.149.131.254167.149.131.255510
67167.149.132.0/23167.149.132.1 to 167.149.133.254167.149.133.255510
68167.149.134.0/23167.149.134.1 to 167.149.135.254167.149.135.255510
69167.149.136.0/23167.149.136.1 to 167.149.137.254167.149.137.255510
70167.149.138.0/23167.149.138.1 to 167.149.139.254167.149.139.255510
71167.149.140.0/23167.149.140.1 to 167.149.141.254167.149.141.255510
72167.149.142.0/23167.149.142.1 to 167.149.143.254167.149.143.255510
73167.149.144.0/23167.149.144.1 to 167.149.145.254167.149.145.255510
74167.149.146.0/23167.149.146.1 to 167.149.147.254167.149.147.255510
75167.149.148.0/23167.149.148.1 to 167.149.149.254167.149.149.255510
76167.149.150.0/23167.149.150.1 to 167.149.151.254167.149.151.255510
77167.149.152.0/23167.149.152.1 to 167.149.153.254167.149.153.255510
78167.149.154.0/23167.149.154.1 to 167.149.155.254167.149.155.255510
79167.149.156.0/23167.149.156.1 to 167.149.157.254167.149.157.255510
80167.149.158.0/23167.149.158.1 to 167.149.159.254167.149.159.255510
81167.149.160.0/23167.149.160.1 to 167.149.161.254167.149.161.255510
82167.149.162.0/23167.149.162.1 to 167.149.163.254167.149.163.255510
83167.149.164.0/23167.149.164.1 to 167.149.165.254167.149.165.255510
84167.149.166.0/23167.149.166.1 to 167.149.167.254167.149.167.255510
85167.149.168.0/23167.149.168.1 to 167.149.169.254167.149.169.255510
86167.149.170.0/23167.149.170.1 to 167.149.171.254167.149.171.255510
87167.149.172.0/23167.149.172.1 to 167.149.173.254167.149.173.255510
88167.149.174.0/23167.149.174.1 to 167.149.175.254167.149.175.255510
89167.149.176.0/23167.149.176.1 to 167.149.177.254167.149.177.255510
90167.149.178.0/23167.149.178.1 to 167.149.179.254167.149.179.255510
91167.149.180.0/23167.149.180.1 to 167.149.181.254167.149.181.255510
92167.149.182.0/23167.149.182.1 to 167.149.183.254167.149.183.255510
93167.149.184.0/23167.149.184.1 to 167.149.185.254167.149.185.255510
94167.149.186.0/23167.149.186.1 to 167.149.187.254167.149.187.255510
95167.149.188.0/23167.149.188.1 to 167.149.189.254167.149.189.255510
96167.149.190.0/23167.149.190.1 to 167.149.191.254167.149.191.255510
97167.149.192.0/23167.149.192.1 to 167.149.193.254167.149.193.255510
98167.149.194.0/23167.149.194.1 to 167.149.195.254167.149.195.255510
99167.149.196.0/23167.149.196.1 to 167.149.197.254167.149.197.255510
100167.149.198.0/23167.149.198.1 to 167.149.199.254167.149.199.255510
101167.149.200.0/23167.149.200.1 to 167.149.201.254167.149.201.255510
102167.149.202.0/23167.149.202.1 to 167.149.203.254167.149.203.255510
103167.149.204.0/23167.149.204.1 to 167.149.205.254167.149.205.255510
104167.149.206.0/23167.149.206.1 to 167.149.207.254167.149.207.255510
105167.149.208.0/23167.149.208.1 to 167.149.209.254167.149.209.255510
106167.149.210.0/23167.149.210.1 to 167.149.211.254167.149.211.255510
107167.149.212.0/23167.149.212.1 to 167.149.213.254167.149.213.255510
108167.149.214.0/23167.149.214.1 to 167.149.215.254167.149.215.255510
109167.149.216.0/23167.149.216.1 to 167.149.217.254167.149.217.255510
110167.149.218.0/23167.149.218.1 to 167.149.219.254167.149.219.255510
111167.149.220.0/23167.149.220.1 to 167.149.221.254167.149.221.255510
112167.149.222.0/23167.149.222.1 to 167.149.223.254167.149.223.255510
113167.149.224.0/23167.149.224.1 to 167.149.225.254167.149.225.255510
114167.149.226.0/23167.149.226.1 to 167.149.227.254167.149.227.255510
115167.149.228.0/23167.149.228.1 to 167.149.229.254167.149.229.255510
116167.149.230.0/23167.149.230.1 to 167.149.231.254167.149.231.255510
117167.149.232.0/23167.149.232.1 to 167.149.233.254167.149.233.255510
118167.149.234.0/23167.149.234.1 to 167.149.235.254167.149.235.255510
119167.149.236.0/23167.149.236.1 to 167.149.237.254167.149.237.255510
120167.149.238.0/23167.149.238.1 to 167.149.239.254167.149.239.255510
121167.149.240.0/23167.149.240.1 to 167.149.241.254167.149.241.255510
122167.149.242.0/23167.149.242.1 to 167.149.243.254167.149.243.255510
123167.149.244.0/23167.149.244.1 to 167.149.245.254167.149.245.255510
124167.149.246.0/23167.149.246.1 to 167.149.247.254167.149.247.255510
125167.149.248.0/23167.149.248.1 to 167.149.249.254167.149.249.255510
126167.149.250.0/23167.149.250.1 to 167.149.251.254167.149.251.255510
127167.149.252.0/23167.149.252.1 to 167.149.253.254167.149.253.255510
128167.149.254.0/23167.149.254.1 to 167.149.255.254167.149.255.255510

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

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.