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.

Network30.64.0.0/14
Usable hosts262,142
Subnet mask255.252.0.0
Addresses262,144
Network address
30.64.0.0
Broadcast address
30.67.255.255
First usable
30.64.0.1
Last usable
30.67.255.254
Usable hosts
262,142 (262,144 less the network and broadcast addresses)
Subnet mask
255.252.0.0
Wildcard mask
0.3.255.255 (Cisco ACLs, OSPF)
Prefix length
/14
Type
Public public
Old class
A (default /8)
As numbers
Hex 1E400000 · Integer 507510784 to 507772927
Reverse DNS zones
64.30.in-addr.arpa
65.30.in-addr.arpa
66.30.in-addr.arpa
67.30.in-addr.arpa
/14 is not on a 8-bit boundary, so it takes 4 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00011110.01000000.00000000.0000000030.64.0.0
Subnet mask11111111.11111100.00000000.00000000255.252.0.0
Network00011110.01000000.00000000.0000000030.64.0.0
Broadcast00011110.01000011.11111111.1111111130.67.255.255
Split into smaller subnets/21
/15 (2)/16 (4)/17 (8)/18 (16)/19 (32)/20 (64)/21 (128)/22 (256)/23 (512)/24 (1,024)/25 (2,048)/26 (4,096)

30.64.0.0/14 makes 128 subnets of /21.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
130.64.0.0/2130.64.0.1 to 30.64.7.25430.64.7.2552,046
230.64.8.0/2130.64.8.1 to 30.64.15.25430.64.15.2552,046
330.64.16.0/2130.64.16.1 to 30.64.23.25430.64.23.2552,046
430.64.24.0/2130.64.24.1 to 30.64.31.25430.64.31.2552,046
530.64.32.0/2130.64.32.1 to 30.64.39.25430.64.39.2552,046
630.64.40.0/2130.64.40.1 to 30.64.47.25430.64.47.2552,046
730.64.48.0/2130.64.48.1 to 30.64.55.25430.64.55.2552,046
830.64.56.0/2130.64.56.1 to 30.64.63.25430.64.63.2552,046
930.64.64.0/2130.64.64.1 to 30.64.71.25430.64.71.2552,046
1030.64.72.0/2130.64.72.1 to 30.64.79.25430.64.79.2552,046
1130.64.80.0/2130.64.80.1 to 30.64.87.25430.64.87.2552,046
1230.64.88.0/2130.64.88.1 to 30.64.95.25430.64.95.2552,046
1330.64.96.0/2130.64.96.1 to 30.64.103.25430.64.103.2552,046
1430.64.104.0/2130.64.104.1 to 30.64.111.25430.64.111.2552,046
1530.64.112.0/2130.64.112.1 to 30.64.119.25430.64.119.2552,046
1630.64.120.0/2130.64.120.1 to 30.64.127.25430.64.127.2552,046
1730.64.128.0/2130.64.128.1 to 30.64.135.25430.64.135.2552,046
1830.64.136.0/2130.64.136.1 to 30.64.143.25430.64.143.2552,046
1930.64.144.0/2130.64.144.1 to 30.64.151.25430.64.151.2552,046
2030.64.152.0/2130.64.152.1 to 30.64.159.25430.64.159.2552,046
2130.64.160.0/2130.64.160.1 to 30.64.167.25430.64.167.2552,046
2230.64.168.0/2130.64.168.1 to 30.64.175.25430.64.175.2552,046
2330.64.176.0/2130.64.176.1 to 30.64.183.25430.64.183.2552,046
2430.64.184.0/2130.64.184.1 to 30.64.191.25430.64.191.2552,046
2530.64.192.0/2130.64.192.1 to 30.64.199.25430.64.199.2552,046
2630.64.200.0/2130.64.200.1 to 30.64.207.25430.64.207.2552,046
2730.64.208.0/2130.64.208.1 to 30.64.215.25430.64.215.2552,046
2830.64.216.0/2130.64.216.1 to 30.64.223.25430.64.223.2552,046
2930.64.224.0/2130.64.224.1 to 30.64.231.25430.64.231.2552,046
3030.64.232.0/2130.64.232.1 to 30.64.239.25430.64.239.2552,046
3130.64.240.0/2130.64.240.1 to 30.64.247.25430.64.247.2552,046
3230.64.248.0/2130.64.248.1 to 30.64.255.25430.64.255.2552,046
3330.65.0.0/2130.65.0.1 to 30.65.7.25430.65.7.2552,046
3430.65.8.0/2130.65.8.1 to 30.65.15.25430.65.15.2552,046
3530.65.16.0/2130.65.16.1 to 30.65.23.25430.65.23.2552,046
3630.65.24.0/2130.65.24.1 to 30.65.31.25430.65.31.2552,046
3730.65.32.0/2130.65.32.1 to 30.65.39.25430.65.39.2552,046
3830.65.40.0/2130.65.40.1 to 30.65.47.25430.65.47.2552,046
3930.65.48.0/2130.65.48.1 to 30.65.55.25430.65.55.2552,046
4030.65.56.0/2130.65.56.1 to 30.65.63.25430.65.63.2552,046
4130.65.64.0/2130.65.64.1 to 30.65.71.25430.65.71.2552,046
4230.65.72.0/2130.65.72.1 to 30.65.79.25430.65.79.2552,046
4330.65.80.0/2130.65.80.1 to 30.65.87.25430.65.87.2552,046
4430.65.88.0/2130.65.88.1 to 30.65.95.25430.65.95.2552,046
4530.65.96.0/2130.65.96.1 to 30.65.103.25430.65.103.2552,046
4630.65.104.0/2130.65.104.1 to 30.65.111.25430.65.111.2552,046
4730.65.112.0/2130.65.112.1 to 30.65.119.25430.65.119.2552,046
4830.65.120.0/2130.65.120.1 to 30.65.127.25430.65.127.2552,046
4930.65.128.0/2130.65.128.1 to 30.65.135.25430.65.135.2552,046
5030.65.136.0/2130.65.136.1 to 30.65.143.25430.65.143.2552,046
5130.65.144.0/2130.65.144.1 to 30.65.151.25430.65.151.2552,046
5230.65.152.0/2130.65.152.1 to 30.65.159.25430.65.159.2552,046
5330.65.160.0/2130.65.160.1 to 30.65.167.25430.65.167.2552,046
5430.65.168.0/2130.65.168.1 to 30.65.175.25430.65.175.2552,046
5530.65.176.0/2130.65.176.1 to 30.65.183.25430.65.183.2552,046
5630.65.184.0/2130.65.184.1 to 30.65.191.25430.65.191.2552,046
5730.65.192.0/2130.65.192.1 to 30.65.199.25430.65.199.2552,046
5830.65.200.0/2130.65.200.1 to 30.65.207.25430.65.207.2552,046
5930.65.208.0/2130.65.208.1 to 30.65.215.25430.65.215.2552,046
6030.65.216.0/2130.65.216.1 to 30.65.223.25430.65.223.2552,046
6130.65.224.0/2130.65.224.1 to 30.65.231.25430.65.231.2552,046
6230.65.232.0/2130.65.232.1 to 30.65.239.25430.65.239.2552,046
6330.65.240.0/2130.65.240.1 to 30.65.247.25430.65.247.2552,046
6430.65.248.0/2130.65.248.1 to 30.65.255.25430.65.255.2552,046
6530.66.0.0/2130.66.0.1 to 30.66.7.25430.66.7.2552,046
6630.66.8.0/2130.66.8.1 to 30.66.15.25430.66.15.2552,046
6730.66.16.0/2130.66.16.1 to 30.66.23.25430.66.23.2552,046
6830.66.24.0/2130.66.24.1 to 30.66.31.25430.66.31.2552,046
6930.66.32.0/2130.66.32.1 to 30.66.39.25430.66.39.2552,046
7030.66.40.0/2130.66.40.1 to 30.66.47.25430.66.47.2552,046
7130.66.48.0/2130.66.48.1 to 30.66.55.25430.66.55.2552,046
7230.66.56.0/2130.66.56.1 to 30.66.63.25430.66.63.2552,046
7330.66.64.0/2130.66.64.1 to 30.66.71.25430.66.71.2552,046
7430.66.72.0/2130.66.72.1 to 30.66.79.25430.66.79.2552,046
7530.66.80.0/2130.66.80.1 to 30.66.87.25430.66.87.2552,046
7630.66.88.0/2130.66.88.1 to 30.66.95.25430.66.95.2552,046
7730.66.96.0/2130.66.96.1 to 30.66.103.25430.66.103.2552,046
7830.66.104.0/2130.66.104.1 to 30.66.111.25430.66.111.2552,046
7930.66.112.0/2130.66.112.1 to 30.66.119.25430.66.119.2552,046
8030.66.120.0/2130.66.120.1 to 30.66.127.25430.66.127.2552,046
8130.66.128.0/2130.66.128.1 to 30.66.135.25430.66.135.2552,046
8230.66.136.0/2130.66.136.1 to 30.66.143.25430.66.143.2552,046
8330.66.144.0/2130.66.144.1 to 30.66.151.25430.66.151.2552,046
8430.66.152.0/2130.66.152.1 to 30.66.159.25430.66.159.2552,046
8530.66.160.0/2130.66.160.1 to 30.66.167.25430.66.167.2552,046
8630.66.168.0/2130.66.168.1 to 30.66.175.25430.66.175.2552,046
8730.66.176.0/2130.66.176.1 to 30.66.183.25430.66.183.2552,046
8830.66.184.0/2130.66.184.1 to 30.66.191.25430.66.191.2552,046
8930.66.192.0/2130.66.192.1 to 30.66.199.25430.66.199.2552,046
9030.66.200.0/2130.66.200.1 to 30.66.207.25430.66.207.2552,046
9130.66.208.0/2130.66.208.1 to 30.66.215.25430.66.215.2552,046
9230.66.216.0/2130.66.216.1 to 30.66.223.25430.66.223.2552,046
9330.66.224.0/2130.66.224.1 to 30.66.231.25430.66.231.2552,046
9430.66.232.0/2130.66.232.1 to 30.66.239.25430.66.239.2552,046
9530.66.240.0/2130.66.240.1 to 30.66.247.25430.66.247.2552,046
9630.66.248.0/2130.66.248.1 to 30.66.255.25430.66.255.2552,046
9730.67.0.0/2130.67.0.1 to 30.67.7.25430.67.7.2552,046
9830.67.8.0/2130.67.8.1 to 30.67.15.25430.67.15.2552,046
9930.67.16.0/2130.67.16.1 to 30.67.23.25430.67.23.2552,046
10030.67.24.0/2130.67.24.1 to 30.67.31.25430.67.31.2552,046
10130.67.32.0/2130.67.32.1 to 30.67.39.25430.67.39.2552,046
10230.67.40.0/2130.67.40.1 to 30.67.47.25430.67.47.2552,046
10330.67.48.0/2130.67.48.1 to 30.67.55.25430.67.55.2552,046
10430.67.56.0/2130.67.56.1 to 30.67.63.25430.67.63.2552,046
10530.67.64.0/2130.67.64.1 to 30.67.71.25430.67.71.2552,046
10630.67.72.0/2130.67.72.1 to 30.67.79.25430.67.79.2552,046
10730.67.80.0/2130.67.80.1 to 30.67.87.25430.67.87.2552,046
10830.67.88.0/2130.67.88.1 to 30.67.95.25430.67.95.2552,046
10930.67.96.0/2130.67.96.1 to 30.67.103.25430.67.103.2552,046
11030.67.104.0/2130.67.104.1 to 30.67.111.25430.67.111.2552,046
11130.67.112.0/2130.67.112.1 to 30.67.119.25430.67.119.2552,046
11230.67.120.0/2130.67.120.1 to 30.67.127.25430.67.127.2552,046
11330.67.128.0/2130.67.128.1 to 30.67.135.25430.67.135.2552,046
11430.67.136.0/2130.67.136.1 to 30.67.143.25430.67.143.2552,046
11530.67.144.0/2130.67.144.1 to 30.67.151.25430.67.151.2552,046
11630.67.152.0/2130.67.152.1 to 30.67.159.25430.67.159.2552,046
11730.67.160.0/2130.67.160.1 to 30.67.167.25430.67.167.2552,046
11830.67.168.0/2130.67.168.1 to 30.67.175.25430.67.175.2552,046
11930.67.176.0/2130.67.176.1 to 30.67.183.25430.67.183.2552,046
12030.67.184.0/2130.67.184.1 to 30.67.191.25430.67.191.2552,046
12130.67.192.0/2130.67.192.1 to 30.67.199.25430.67.199.2552,046
12230.67.200.0/2130.67.200.1 to 30.67.207.25430.67.207.2552,046
12330.67.208.0/2130.67.208.1 to 30.67.215.25430.67.215.2552,046
12430.67.216.0/2130.67.216.1 to 30.67.223.25430.67.223.2552,046
12530.67.224.0/2130.67.224.1 to 30.67.231.25430.67.231.2552,046
12630.67.232.0/2130.67.232.1 to 30.67.239.25430.67.239.2552,046
12730.67.240.0/2130.67.240.1 to 30.67.247.25430.67.247.2552,046
12830.67.248.0/2130.67.248.1 to 30.67.255.25430.67.255.2552,046

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.