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.

Network169.254.0.0/16
Usable hosts65,534
Subnet mask255.255.0.0
Addresses65,536
Network address
169.254.0.0
Broadcast address
169.254.255.255
First usable
169.254.0.1
Last usable
169.254.255.254
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
Link-local (APIPA) 169.254.0.0/16
Self-assigned when no DHCP server answers
Old class
B (default /16)
As numbers
Hex A9FE0000 · Integer 2851995648 to 2852061183
Reverse DNS zone
254.169.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10101001.11111110..00000000.00000000169.254.0.0
Subnet mask11111111.11111111..00000000.00000000255.255.0.0
Network10101001.11111110..00000000.00000000169.254.0.0
Broadcast10101001.11111110..11111111.11111111169.254.255.255
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)

169.254.0.0/16 makes 128 subnets of /23.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1169.254.0.0/23169.254.0.1 to 169.254.1.254169.254.1.255510
2169.254.2.0/23169.254.2.1 to 169.254.3.254169.254.3.255510
3169.254.4.0/23169.254.4.1 to 169.254.5.254169.254.5.255510
4169.254.6.0/23169.254.6.1 to 169.254.7.254169.254.7.255510
5169.254.8.0/23169.254.8.1 to 169.254.9.254169.254.9.255510
6169.254.10.0/23169.254.10.1 to 169.254.11.254169.254.11.255510
7169.254.12.0/23169.254.12.1 to 169.254.13.254169.254.13.255510
8169.254.14.0/23169.254.14.1 to 169.254.15.254169.254.15.255510
9169.254.16.0/23169.254.16.1 to 169.254.17.254169.254.17.255510
10169.254.18.0/23169.254.18.1 to 169.254.19.254169.254.19.255510
11169.254.20.0/23169.254.20.1 to 169.254.21.254169.254.21.255510
12169.254.22.0/23169.254.22.1 to 169.254.23.254169.254.23.255510
13169.254.24.0/23169.254.24.1 to 169.254.25.254169.254.25.255510
14169.254.26.0/23169.254.26.1 to 169.254.27.254169.254.27.255510
15169.254.28.0/23169.254.28.1 to 169.254.29.254169.254.29.255510
16169.254.30.0/23169.254.30.1 to 169.254.31.254169.254.31.255510
17169.254.32.0/23169.254.32.1 to 169.254.33.254169.254.33.255510
18169.254.34.0/23169.254.34.1 to 169.254.35.254169.254.35.255510
19169.254.36.0/23169.254.36.1 to 169.254.37.254169.254.37.255510
20169.254.38.0/23169.254.38.1 to 169.254.39.254169.254.39.255510
21169.254.40.0/23169.254.40.1 to 169.254.41.254169.254.41.255510
22169.254.42.0/23169.254.42.1 to 169.254.43.254169.254.43.255510
23169.254.44.0/23169.254.44.1 to 169.254.45.254169.254.45.255510
24169.254.46.0/23169.254.46.1 to 169.254.47.254169.254.47.255510
25169.254.48.0/23169.254.48.1 to 169.254.49.254169.254.49.255510
26169.254.50.0/23169.254.50.1 to 169.254.51.254169.254.51.255510
27169.254.52.0/23169.254.52.1 to 169.254.53.254169.254.53.255510
28169.254.54.0/23169.254.54.1 to 169.254.55.254169.254.55.255510
29169.254.56.0/23169.254.56.1 to 169.254.57.254169.254.57.255510
30169.254.58.0/23169.254.58.1 to 169.254.59.254169.254.59.255510
31169.254.60.0/23169.254.60.1 to 169.254.61.254169.254.61.255510
32169.254.62.0/23169.254.62.1 to 169.254.63.254169.254.63.255510
33169.254.64.0/23169.254.64.1 to 169.254.65.254169.254.65.255510
34169.254.66.0/23169.254.66.1 to 169.254.67.254169.254.67.255510
35169.254.68.0/23169.254.68.1 to 169.254.69.254169.254.69.255510
36169.254.70.0/23169.254.70.1 to 169.254.71.254169.254.71.255510
37169.254.72.0/23169.254.72.1 to 169.254.73.254169.254.73.255510
38169.254.74.0/23169.254.74.1 to 169.254.75.254169.254.75.255510
39169.254.76.0/23169.254.76.1 to 169.254.77.254169.254.77.255510
40169.254.78.0/23169.254.78.1 to 169.254.79.254169.254.79.255510
41169.254.80.0/23169.254.80.1 to 169.254.81.254169.254.81.255510
42169.254.82.0/23169.254.82.1 to 169.254.83.254169.254.83.255510
43169.254.84.0/23169.254.84.1 to 169.254.85.254169.254.85.255510
44169.254.86.0/23169.254.86.1 to 169.254.87.254169.254.87.255510
45169.254.88.0/23169.254.88.1 to 169.254.89.254169.254.89.255510
46169.254.90.0/23169.254.90.1 to 169.254.91.254169.254.91.255510
47169.254.92.0/23169.254.92.1 to 169.254.93.254169.254.93.255510
48169.254.94.0/23169.254.94.1 to 169.254.95.254169.254.95.255510
49169.254.96.0/23169.254.96.1 to 169.254.97.254169.254.97.255510
50169.254.98.0/23169.254.98.1 to 169.254.99.254169.254.99.255510
51169.254.100.0/23169.254.100.1 to 169.254.101.254169.254.101.255510
52169.254.102.0/23169.254.102.1 to 169.254.103.254169.254.103.255510
53169.254.104.0/23169.254.104.1 to 169.254.105.254169.254.105.255510
54169.254.106.0/23169.254.106.1 to 169.254.107.254169.254.107.255510
55169.254.108.0/23169.254.108.1 to 169.254.109.254169.254.109.255510
56169.254.110.0/23169.254.110.1 to 169.254.111.254169.254.111.255510
57169.254.112.0/23169.254.112.1 to 169.254.113.254169.254.113.255510
58169.254.114.0/23169.254.114.1 to 169.254.115.254169.254.115.255510
59169.254.116.0/23169.254.116.1 to 169.254.117.254169.254.117.255510
60169.254.118.0/23169.254.118.1 to 169.254.119.254169.254.119.255510
61169.254.120.0/23169.254.120.1 to 169.254.121.254169.254.121.255510
62169.254.122.0/23169.254.122.1 to 169.254.123.254169.254.123.255510
63169.254.124.0/23169.254.124.1 to 169.254.125.254169.254.125.255510
64169.254.126.0/23169.254.126.1 to 169.254.127.254169.254.127.255510
65169.254.128.0/23169.254.128.1 to 169.254.129.254169.254.129.255510
66169.254.130.0/23169.254.130.1 to 169.254.131.254169.254.131.255510
67169.254.132.0/23169.254.132.1 to 169.254.133.254169.254.133.255510
68169.254.134.0/23169.254.134.1 to 169.254.135.254169.254.135.255510
69169.254.136.0/23169.254.136.1 to 169.254.137.254169.254.137.255510
70169.254.138.0/23169.254.138.1 to 169.254.139.254169.254.139.255510
71169.254.140.0/23169.254.140.1 to 169.254.141.254169.254.141.255510
72169.254.142.0/23169.254.142.1 to 169.254.143.254169.254.143.255510
73169.254.144.0/23169.254.144.1 to 169.254.145.254169.254.145.255510
74169.254.146.0/23169.254.146.1 to 169.254.147.254169.254.147.255510
75169.254.148.0/23169.254.148.1 to 169.254.149.254169.254.149.255510
76169.254.150.0/23169.254.150.1 to 169.254.151.254169.254.151.255510
77169.254.152.0/23169.254.152.1 to 169.254.153.254169.254.153.255510
78169.254.154.0/23169.254.154.1 to 169.254.155.254169.254.155.255510
79169.254.156.0/23169.254.156.1 to 169.254.157.254169.254.157.255510
80169.254.158.0/23169.254.158.1 to 169.254.159.254169.254.159.255510
81169.254.160.0/23169.254.160.1 to 169.254.161.254169.254.161.255510
82169.254.162.0/23169.254.162.1 to 169.254.163.254169.254.163.255510
83169.254.164.0/23169.254.164.1 to 169.254.165.254169.254.165.255510
84169.254.166.0/23169.254.166.1 to 169.254.167.254169.254.167.255510
85169.254.168.0/23169.254.168.1 to 169.254.169.254169.254.169.255510
86169.254.170.0/23169.254.170.1 to 169.254.171.254169.254.171.255510
87169.254.172.0/23169.254.172.1 to 169.254.173.254169.254.173.255510
88169.254.174.0/23169.254.174.1 to 169.254.175.254169.254.175.255510
89169.254.176.0/23169.254.176.1 to 169.254.177.254169.254.177.255510
90169.254.178.0/23169.254.178.1 to 169.254.179.254169.254.179.255510
91169.254.180.0/23169.254.180.1 to 169.254.181.254169.254.181.255510
92169.254.182.0/23169.254.182.1 to 169.254.183.254169.254.183.255510
93169.254.184.0/23169.254.184.1 to 169.254.185.254169.254.185.255510
94169.254.186.0/23169.254.186.1 to 169.254.187.254169.254.187.255510
95169.254.188.0/23169.254.188.1 to 169.254.189.254169.254.189.255510
96169.254.190.0/23169.254.190.1 to 169.254.191.254169.254.191.255510
97169.254.192.0/23169.254.192.1 to 169.254.193.254169.254.193.255510
98169.254.194.0/23169.254.194.1 to 169.254.195.254169.254.195.255510
99169.254.196.0/23169.254.196.1 to 169.254.197.254169.254.197.255510
100169.254.198.0/23169.254.198.1 to 169.254.199.254169.254.199.255510
101169.254.200.0/23169.254.200.1 to 169.254.201.254169.254.201.255510
102169.254.202.0/23169.254.202.1 to 169.254.203.254169.254.203.255510
103169.254.204.0/23169.254.204.1 to 169.254.205.254169.254.205.255510
104169.254.206.0/23169.254.206.1 to 169.254.207.254169.254.207.255510
105169.254.208.0/23169.254.208.1 to 169.254.209.254169.254.209.255510
106169.254.210.0/23169.254.210.1 to 169.254.211.254169.254.211.255510
107169.254.212.0/23169.254.212.1 to 169.254.213.254169.254.213.255510
108169.254.214.0/23169.254.214.1 to 169.254.215.254169.254.215.255510
109169.254.216.0/23169.254.216.1 to 169.254.217.254169.254.217.255510
110169.254.218.0/23169.254.218.1 to 169.254.219.254169.254.219.255510
111169.254.220.0/23169.254.220.1 to 169.254.221.254169.254.221.255510
112169.254.222.0/23169.254.222.1 to 169.254.223.254169.254.223.255510
113169.254.224.0/23169.254.224.1 to 169.254.225.254169.254.225.255510
114169.254.226.0/23169.254.226.1 to 169.254.227.254169.254.227.255510
115169.254.228.0/23169.254.228.1 to 169.254.229.254169.254.229.255510
116169.254.230.0/23169.254.230.1 to 169.254.231.254169.254.231.255510
117169.254.232.0/23169.254.232.1 to 169.254.233.254169.254.233.255510
118169.254.234.0/23169.254.234.1 to 169.254.235.254169.254.235.255510
119169.254.236.0/23169.254.236.1 to 169.254.237.254169.254.237.255510
120169.254.238.0/23169.254.238.1 to 169.254.239.254169.254.239.255510
121169.254.240.0/23169.254.240.1 to 169.254.241.254169.254.241.255510
122169.254.242.0/23169.254.242.1 to 169.254.243.254169.254.243.255510
123169.254.244.0/23169.254.244.1 to 169.254.245.254169.254.245.255510
124169.254.246.0/23169.254.246.1 to 169.254.247.254169.254.247.255510
125169.254.248.0/23169.254.248.1 to 169.254.249.254169.254.249.255510
126169.254.250.0/23169.254.250.1 to 169.254.251.254169.254.251.255510
127169.254.252.0/23169.254.252.1 to 169.254.253.254169.254.253.255510
128169.254.254.0/23169.254.254.1 to 169.254.255.254169.254.255.255510

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.