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.

Network84.0.0.0/8
Usable hosts16,777,214
Subnet mask255.0.0.0
Addresses16,777,216
Network address
84.0.0.0
Broadcast address
84.255.255.255
First usable
84.0.0.1
Last usable
84.255.255.254
Usable hosts
16,777,214 (16,777,216 less the network and broadcast addresses)
Subnet mask
255.0.0.0
Wildcard mask
0.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/8
Type
Public public
Old class
A (default /8)
As numbers
Hex 54000000 · Integer 1409286144 to 1426063359
Reverse DNS zone
84.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address01010100..00000000.00000000.0000000084.0.0.0
Subnet mask11111111..00000000.00000000.00000000255.0.0.0
Network01010100..00000000.00000000.0000000084.0.0.0
Broadcast01010100..11111111.11111111.1111111184.255.255.255
Split into smaller subnets/15
/9 (2)/10 (4)/11 (8)/12 (16)/13 (32)/14 (64)/15 (128)/16 (256)/17 (512)/18 (1,024)/19 (2,048)/20 (4,096)

84.0.0.0/8 makes 128 subnets of /15.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
184.0.0.0/1584.0.0.1 to 84.1.255.25484.1.255.255131,070
284.2.0.0/1584.2.0.1 to 84.3.255.25484.3.255.255131,070
384.4.0.0/1584.4.0.1 to 84.5.255.25484.5.255.255131,070
484.6.0.0/1584.6.0.1 to 84.7.255.25484.7.255.255131,070
584.8.0.0/1584.8.0.1 to 84.9.255.25484.9.255.255131,070
684.10.0.0/1584.10.0.1 to 84.11.255.25484.11.255.255131,070
784.12.0.0/1584.12.0.1 to 84.13.255.25484.13.255.255131,070
884.14.0.0/1584.14.0.1 to 84.15.255.25484.15.255.255131,070
984.16.0.0/1584.16.0.1 to 84.17.255.25484.17.255.255131,070
1084.18.0.0/1584.18.0.1 to 84.19.255.25484.19.255.255131,070
1184.20.0.0/1584.20.0.1 to 84.21.255.25484.21.255.255131,070
1284.22.0.0/1584.22.0.1 to 84.23.255.25484.23.255.255131,070
1384.24.0.0/1584.24.0.1 to 84.25.255.25484.25.255.255131,070
1484.26.0.0/1584.26.0.1 to 84.27.255.25484.27.255.255131,070
1584.28.0.0/1584.28.0.1 to 84.29.255.25484.29.255.255131,070
1684.30.0.0/1584.30.0.1 to 84.31.255.25484.31.255.255131,070
1784.32.0.0/1584.32.0.1 to 84.33.255.25484.33.255.255131,070
1884.34.0.0/1584.34.0.1 to 84.35.255.25484.35.255.255131,070
1984.36.0.0/1584.36.0.1 to 84.37.255.25484.37.255.255131,070
2084.38.0.0/1584.38.0.1 to 84.39.255.25484.39.255.255131,070
2184.40.0.0/1584.40.0.1 to 84.41.255.25484.41.255.255131,070
2284.42.0.0/1584.42.0.1 to 84.43.255.25484.43.255.255131,070
2384.44.0.0/1584.44.0.1 to 84.45.255.25484.45.255.255131,070
2484.46.0.0/1584.46.0.1 to 84.47.255.25484.47.255.255131,070
2584.48.0.0/1584.48.0.1 to 84.49.255.25484.49.255.255131,070
2684.50.0.0/1584.50.0.1 to 84.51.255.25484.51.255.255131,070
2784.52.0.0/1584.52.0.1 to 84.53.255.25484.53.255.255131,070
2884.54.0.0/1584.54.0.1 to 84.55.255.25484.55.255.255131,070
2984.56.0.0/1584.56.0.1 to 84.57.255.25484.57.255.255131,070
3084.58.0.0/1584.58.0.1 to 84.59.255.25484.59.255.255131,070
3184.60.0.0/1584.60.0.1 to 84.61.255.25484.61.255.255131,070
3284.62.0.0/1584.62.0.1 to 84.63.255.25484.63.255.255131,070
3384.64.0.0/1584.64.0.1 to 84.65.255.25484.65.255.255131,070
3484.66.0.0/1584.66.0.1 to 84.67.255.25484.67.255.255131,070
3584.68.0.0/1584.68.0.1 to 84.69.255.25484.69.255.255131,070
3684.70.0.0/1584.70.0.1 to 84.71.255.25484.71.255.255131,070
3784.72.0.0/1584.72.0.1 to 84.73.255.25484.73.255.255131,070
3884.74.0.0/1584.74.0.1 to 84.75.255.25484.75.255.255131,070
3984.76.0.0/1584.76.0.1 to 84.77.255.25484.77.255.255131,070
4084.78.0.0/1584.78.0.1 to 84.79.255.25484.79.255.255131,070
4184.80.0.0/1584.80.0.1 to 84.81.255.25484.81.255.255131,070
4284.82.0.0/1584.82.0.1 to 84.83.255.25484.83.255.255131,070
4384.84.0.0/1584.84.0.1 to 84.85.255.25484.85.255.255131,070
4484.86.0.0/1584.86.0.1 to 84.87.255.25484.87.255.255131,070
4584.88.0.0/1584.88.0.1 to 84.89.255.25484.89.255.255131,070
4684.90.0.0/1584.90.0.1 to 84.91.255.25484.91.255.255131,070
4784.92.0.0/1584.92.0.1 to 84.93.255.25484.93.255.255131,070
4884.94.0.0/1584.94.0.1 to 84.95.255.25484.95.255.255131,070
4984.96.0.0/1584.96.0.1 to 84.97.255.25484.97.255.255131,070
5084.98.0.0/1584.98.0.1 to 84.99.255.25484.99.255.255131,070
5184.100.0.0/1584.100.0.1 to 84.101.255.25484.101.255.255131,070
5284.102.0.0/1584.102.0.1 to 84.103.255.25484.103.255.255131,070
5384.104.0.0/1584.104.0.1 to 84.105.255.25484.105.255.255131,070
5484.106.0.0/1584.106.0.1 to 84.107.255.25484.107.255.255131,070
5584.108.0.0/1584.108.0.1 to 84.109.255.25484.109.255.255131,070
5684.110.0.0/1584.110.0.1 to 84.111.255.25484.111.255.255131,070
5784.112.0.0/1584.112.0.1 to 84.113.255.25484.113.255.255131,070
5884.114.0.0/1584.114.0.1 to 84.115.255.25484.115.255.255131,070
5984.116.0.0/1584.116.0.1 to 84.117.255.25484.117.255.255131,070
6084.118.0.0/1584.118.0.1 to 84.119.255.25484.119.255.255131,070
6184.120.0.0/1584.120.0.1 to 84.121.255.25484.121.255.255131,070
6284.122.0.0/1584.122.0.1 to 84.123.255.25484.123.255.255131,070
6384.124.0.0/1584.124.0.1 to 84.125.255.25484.125.255.255131,070
6484.126.0.0/1584.126.0.1 to 84.127.255.25484.127.255.255131,070
6584.128.0.0/1584.128.0.1 to 84.129.255.25484.129.255.255131,070
6684.130.0.0/1584.130.0.1 to 84.131.255.25484.131.255.255131,070
6784.132.0.0/1584.132.0.1 to 84.133.255.25484.133.255.255131,070
6884.134.0.0/1584.134.0.1 to 84.135.255.25484.135.255.255131,070
6984.136.0.0/1584.136.0.1 to 84.137.255.25484.137.255.255131,070
7084.138.0.0/1584.138.0.1 to 84.139.255.25484.139.255.255131,070
7184.140.0.0/1584.140.0.1 to 84.141.255.25484.141.255.255131,070
7284.142.0.0/1584.142.0.1 to 84.143.255.25484.143.255.255131,070
7384.144.0.0/1584.144.0.1 to 84.145.255.25484.145.255.255131,070
7484.146.0.0/1584.146.0.1 to 84.147.255.25484.147.255.255131,070
7584.148.0.0/1584.148.0.1 to 84.149.255.25484.149.255.255131,070
7684.150.0.0/1584.150.0.1 to 84.151.255.25484.151.255.255131,070
7784.152.0.0/1584.152.0.1 to 84.153.255.25484.153.255.255131,070
7884.154.0.0/1584.154.0.1 to 84.155.255.25484.155.255.255131,070
7984.156.0.0/1584.156.0.1 to 84.157.255.25484.157.255.255131,070
8084.158.0.0/1584.158.0.1 to 84.159.255.25484.159.255.255131,070
8184.160.0.0/1584.160.0.1 to 84.161.255.25484.161.255.255131,070
8284.162.0.0/1584.162.0.1 to 84.163.255.25484.163.255.255131,070
8384.164.0.0/1584.164.0.1 to 84.165.255.25484.165.255.255131,070
8484.166.0.0/1584.166.0.1 to 84.167.255.25484.167.255.255131,070
8584.168.0.0/1584.168.0.1 to 84.169.255.25484.169.255.255131,070
8684.170.0.0/1584.170.0.1 to 84.171.255.25484.171.255.255131,070
8784.172.0.0/1584.172.0.1 to 84.173.255.25484.173.255.255131,070
8884.174.0.0/1584.174.0.1 to 84.175.255.25484.175.255.255131,070
8984.176.0.0/1584.176.0.1 to 84.177.255.25484.177.255.255131,070
9084.178.0.0/1584.178.0.1 to 84.179.255.25484.179.255.255131,070
9184.180.0.0/1584.180.0.1 to 84.181.255.25484.181.255.255131,070
9284.182.0.0/1584.182.0.1 to 84.183.255.25484.183.255.255131,070
9384.184.0.0/1584.184.0.1 to 84.185.255.25484.185.255.255131,070
9484.186.0.0/1584.186.0.1 to 84.187.255.25484.187.255.255131,070
9584.188.0.0/1584.188.0.1 to 84.189.255.25484.189.255.255131,070
9684.190.0.0/1584.190.0.1 to 84.191.255.25484.191.255.255131,070
9784.192.0.0/1584.192.0.1 to 84.193.255.25484.193.255.255131,070
9884.194.0.0/1584.194.0.1 to 84.195.255.25484.195.255.255131,070
9984.196.0.0/1584.196.0.1 to 84.197.255.25484.197.255.255131,070
10084.198.0.0/1584.198.0.1 to 84.199.255.25484.199.255.255131,070
10184.200.0.0/1584.200.0.1 to 84.201.255.25484.201.255.255131,070
10284.202.0.0/1584.202.0.1 to 84.203.255.25484.203.255.255131,070
10384.204.0.0/1584.204.0.1 to 84.205.255.25484.205.255.255131,070
10484.206.0.0/1584.206.0.1 to 84.207.255.25484.207.255.255131,070
10584.208.0.0/1584.208.0.1 to 84.209.255.25484.209.255.255131,070
10684.210.0.0/1584.210.0.1 to 84.211.255.25484.211.255.255131,070
10784.212.0.0/1584.212.0.1 to 84.213.255.25484.213.255.255131,070
10884.214.0.0/1584.214.0.1 to 84.215.255.25484.215.255.255131,070
10984.216.0.0/1584.216.0.1 to 84.217.255.25484.217.255.255131,070
11084.218.0.0/1584.218.0.1 to 84.219.255.25484.219.255.255131,070
11184.220.0.0/1584.220.0.1 to 84.221.255.25484.221.255.255131,070
11284.222.0.0/1584.222.0.1 to 84.223.255.25484.223.255.255131,070
11384.224.0.0/1584.224.0.1 to 84.225.255.25484.225.255.255131,070
11484.226.0.0/1584.226.0.1 to 84.227.255.25484.227.255.255131,070
11584.228.0.0/1584.228.0.1 to 84.229.255.25484.229.255.255131,070
11684.230.0.0/1584.230.0.1 to 84.231.255.25484.231.255.255131,070
11784.232.0.0/1584.232.0.1 to 84.233.255.25484.233.255.255131,070
11884.234.0.0/1584.234.0.1 to 84.235.255.25484.235.255.255131,070
11984.236.0.0/1584.236.0.1 to 84.237.255.25484.237.255.255131,070
12084.238.0.0/1584.238.0.1 to 84.239.255.25484.239.255.255131,070
12184.240.0.0/1584.240.0.1 to 84.241.255.25484.241.255.255131,070
12284.242.0.0/1584.242.0.1 to 84.243.255.25484.243.255.255131,070
12384.244.0.0/1584.244.0.1 to 84.245.255.25484.245.255.255131,070
12484.246.0.0/1584.246.0.1 to 84.247.255.25484.247.255.255131,070
12584.248.0.0/1584.248.0.1 to 84.249.255.25484.249.255.255131,070
12684.250.0.0/1584.250.0.1 to 84.251.255.25484.251.255.255131,070
12784.252.0.0/1584.252.0.1 to 84.253.255.25484.253.255.255131,070
12884.254.0.0/1584.254.0.1 to 84.255.255.25484.255.255.255131,070

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.