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.

Network14.96.0.0/11
Usable hosts2,097,150
Subnet mask255.224.0.0
Addresses2,097,152
Network address
14.96.0.0
Broadcast address
14.127.255.255
First usable
14.96.0.1
Last usable
14.127.255.254
Usable hosts
2,097,150 (2,097,152 less the network and broadcast addresses)
Subnet mask
255.224.0.0
Wildcard mask
0.31.255.255 (Cisco ACLs, OSPF)
Prefix length
/11
Type
Public public
Old class
A (default /8)
As numbers
Hex 0E600000 · Integer 241172480 to 243269631
Reverse DNS zones
96.14.in-addr.arpa
97.14.in-addr.arpa
98.14.in-addr.arpa
99.14.in-addr.arpa
100.14.in-addr.arpa
101.14.in-addr.arpa
102.14.in-addr.arpa
103.14.in-addr.arpa
104.14.in-addr.arpa
105.14.in-addr.arpa
106.14.in-addr.arpa
107.14.in-addr.arpa
108.14.in-addr.arpa
109.14.in-addr.arpa
110.14.in-addr.arpa
111.14.in-addr.arpa
and 16 more
/11 is not on a 8-bit boundary, so it takes 32 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00001110.01100000.00000000.0000000014.96.0.0
Subnet mask11111111.11100000.00000000.00000000255.224.0.0
Network00001110.01100000.00000000.0000000014.96.0.0
Broadcast00001110.01111111.11111111.1111111114.127.255.255
Split into smaller subnets/18
/12 (2)/13 (4)/14 (8)/15 (16)/16 (32)/17 (64)/18 (128)/19 (256)/20 (512)/21 (1,024)/22 (2,048)/23 (4,096)

14.96.0.0/11 makes 128 subnets of /18.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
114.96.0.0/1814.96.0.1 to 14.96.63.25414.96.63.25516,382
214.96.64.0/1814.96.64.1 to 14.96.127.25414.96.127.25516,382
314.96.128.0/1814.96.128.1 to 14.96.191.25414.96.191.25516,382
414.96.192.0/1814.96.192.1 to 14.96.255.25414.96.255.25516,382
514.97.0.0/1814.97.0.1 to 14.97.63.25414.97.63.25516,382
614.97.64.0/1814.97.64.1 to 14.97.127.25414.97.127.25516,382
714.97.128.0/1814.97.128.1 to 14.97.191.25414.97.191.25516,382
814.97.192.0/1814.97.192.1 to 14.97.255.25414.97.255.25516,382
914.98.0.0/1814.98.0.1 to 14.98.63.25414.98.63.25516,382
1014.98.64.0/1814.98.64.1 to 14.98.127.25414.98.127.25516,382
1114.98.128.0/1814.98.128.1 to 14.98.191.25414.98.191.25516,382
1214.98.192.0/1814.98.192.1 to 14.98.255.25414.98.255.25516,382
1314.99.0.0/1814.99.0.1 to 14.99.63.25414.99.63.25516,382
1414.99.64.0/1814.99.64.1 to 14.99.127.25414.99.127.25516,382
1514.99.128.0/1814.99.128.1 to 14.99.191.25414.99.191.25516,382
1614.99.192.0/1814.99.192.1 to 14.99.255.25414.99.255.25516,382
1714.100.0.0/1814.100.0.1 to 14.100.63.25414.100.63.25516,382
1814.100.64.0/1814.100.64.1 to 14.100.127.25414.100.127.25516,382
1914.100.128.0/1814.100.128.1 to 14.100.191.25414.100.191.25516,382
2014.100.192.0/1814.100.192.1 to 14.100.255.25414.100.255.25516,382
2114.101.0.0/1814.101.0.1 to 14.101.63.25414.101.63.25516,382
2214.101.64.0/1814.101.64.1 to 14.101.127.25414.101.127.25516,382
2314.101.128.0/1814.101.128.1 to 14.101.191.25414.101.191.25516,382
2414.101.192.0/1814.101.192.1 to 14.101.255.25414.101.255.25516,382
2514.102.0.0/1814.102.0.1 to 14.102.63.25414.102.63.25516,382
2614.102.64.0/1814.102.64.1 to 14.102.127.25414.102.127.25516,382
2714.102.128.0/1814.102.128.1 to 14.102.191.25414.102.191.25516,382
2814.102.192.0/1814.102.192.1 to 14.102.255.25414.102.255.25516,382
2914.103.0.0/1814.103.0.1 to 14.103.63.25414.103.63.25516,382
3014.103.64.0/1814.103.64.1 to 14.103.127.25414.103.127.25516,382
3114.103.128.0/1814.103.128.1 to 14.103.191.25414.103.191.25516,382
3214.103.192.0/1814.103.192.1 to 14.103.255.25414.103.255.25516,382
3314.104.0.0/1814.104.0.1 to 14.104.63.25414.104.63.25516,382
3414.104.64.0/1814.104.64.1 to 14.104.127.25414.104.127.25516,382
3514.104.128.0/1814.104.128.1 to 14.104.191.25414.104.191.25516,382
3614.104.192.0/1814.104.192.1 to 14.104.255.25414.104.255.25516,382
3714.105.0.0/1814.105.0.1 to 14.105.63.25414.105.63.25516,382
3814.105.64.0/1814.105.64.1 to 14.105.127.25414.105.127.25516,382
3914.105.128.0/1814.105.128.1 to 14.105.191.25414.105.191.25516,382
4014.105.192.0/1814.105.192.1 to 14.105.255.25414.105.255.25516,382
4114.106.0.0/1814.106.0.1 to 14.106.63.25414.106.63.25516,382
4214.106.64.0/1814.106.64.1 to 14.106.127.25414.106.127.25516,382
4314.106.128.0/1814.106.128.1 to 14.106.191.25414.106.191.25516,382
4414.106.192.0/1814.106.192.1 to 14.106.255.25414.106.255.25516,382
4514.107.0.0/1814.107.0.1 to 14.107.63.25414.107.63.25516,382
4614.107.64.0/1814.107.64.1 to 14.107.127.25414.107.127.25516,382
4714.107.128.0/1814.107.128.1 to 14.107.191.25414.107.191.25516,382
4814.107.192.0/1814.107.192.1 to 14.107.255.25414.107.255.25516,382
4914.108.0.0/1814.108.0.1 to 14.108.63.25414.108.63.25516,382
5014.108.64.0/1814.108.64.1 to 14.108.127.25414.108.127.25516,382
5114.108.128.0/1814.108.128.1 to 14.108.191.25414.108.191.25516,382
5214.108.192.0/1814.108.192.1 to 14.108.255.25414.108.255.25516,382
5314.109.0.0/1814.109.0.1 to 14.109.63.25414.109.63.25516,382
5414.109.64.0/1814.109.64.1 to 14.109.127.25414.109.127.25516,382
5514.109.128.0/1814.109.128.1 to 14.109.191.25414.109.191.25516,382
5614.109.192.0/1814.109.192.1 to 14.109.255.25414.109.255.25516,382
5714.110.0.0/1814.110.0.1 to 14.110.63.25414.110.63.25516,382
5814.110.64.0/1814.110.64.1 to 14.110.127.25414.110.127.25516,382
5914.110.128.0/1814.110.128.1 to 14.110.191.25414.110.191.25516,382
6014.110.192.0/1814.110.192.1 to 14.110.255.25414.110.255.25516,382
6114.111.0.0/1814.111.0.1 to 14.111.63.25414.111.63.25516,382
6214.111.64.0/1814.111.64.1 to 14.111.127.25414.111.127.25516,382
6314.111.128.0/1814.111.128.1 to 14.111.191.25414.111.191.25516,382
6414.111.192.0/1814.111.192.1 to 14.111.255.25414.111.255.25516,382
6514.112.0.0/1814.112.0.1 to 14.112.63.25414.112.63.25516,382
6614.112.64.0/1814.112.64.1 to 14.112.127.25414.112.127.25516,382
6714.112.128.0/1814.112.128.1 to 14.112.191.25414.112.191.25516,382
6814.112.192.0/1814.112.192.1 to 14.112.255.25414.112.255.25516,382
6914.113.0.0/1814.113.0.1 to 14.113.63.25414.113.63.25516,382
7014.113.64.0/1814.113.64.1 to 14.113.127.25414.113.127.25516,382
7114.113.128.0/1814.113.128.1 to 14.113.191.25414.113.191.25516,382
7214.113.192.0/1814.113.192.1 to 14.113.255.25414.113.255.25516,382
7314.114.0.0/1814.114.0.1 to 14.114.63.25414.114.63.25516,382
7414.114.64.0/1814.114.64.1 to 14.114.127.25414.114.127.25516,382
7514.114.128.0/1814.114.128.1 to 14.114.191.25414.114.191.25516,382
7614.114.192.0/1814.114.192.1 to 14.114.255.25414.114.255.25516,382
7714.115.0.0/1814.115.0.1 to 14.115.63.25414.115.63.25516,382
7814.115.64.0/1814.115.64.1 to 14.115.127.25414.115.127.25516,382
7914.115.128.0/1814.115.128.1 to 14.115.191.25414.115.191.25516,382
8014.115.192.0/1814.115.192.1 to 14.115.255.25414.115.255.25516,382
8114.116.0.0/1814.116.0.1 to 14.116.63.25414.116.63.25516,382
8214.116.64.0/1814.116.64.1 to 14.116.127.25414.116.127.25516,382
8314.116.128.0/1814.116.128.1 to 14.116.191.25414.116.191.25516,382
8414.116.192.0/1814.116.192.1 to 14.116.255.25414.116.255.25516,382
8514.117.0.0/1814.117.0.1 to 14.117.63.25414.117.63.25516,382
8614.117.64.0/1814.117.64.1 to 14.117.127.25414.117.127.25516,382
8714.117.128.0/1814.117.128.1 to 14.117.191.25414.117.191.25516,382
8814.117.192.0/1814.117.192.1 to 14.117.255.25414.117.255.25516,382
8914.118.0.0/1814.118.0.1 to 14.118.63.25414.118.63.25516,382
9014.118.64.0/1814.118.64.1 to 14.118.127.25414.118.127.25516,382
9114.118.128.0/1814.118.128.1 to 14.118.191.25414.118.191.25516,382
9214.118.192.0/1814.118.192.1 to 14.118.255.25414.118.255.25516,382
9314.119.0.0/1814.119.0.1 to 14.119.63.25414.119.63.25516,382
9414.119.64.0/1814.119.64.1 to 14.119.127.25414.119.127.25516,382
9514.119.128.0/1814.119.128.1 to 14.119.191.25414.119.191.25516,382
9614.119.192.0/1814.119.192.1 to 14.119.255.25414.119.255.25516,382
9714.120.0.0/1814.120.0.1 to 14.120.63.25414.120.63.25516,382
9814.120.64.0/1814.120.64.1 to 14.120.127.25414.120.127.25516,382
9914.120.128.0/1814.120.128.1 to 14.120.191.25414.120.191.25516,382
10014.120.192.0/1814.120.192.1 to 14.120.255.25414.120.255.25516,382
10114.121.0.0/1814.121.0.1 to 14.121.63.25414.121.63.25516,382
10214.121.64.0/1814.121.64.1 to 14.121.127.25414.121.127.25516,382
10314.121.128.0/1814.121.128.1 to 14.121.191.25414.121.191.25516,382
10414.121.192.0/1814.121.192.1 to 14.121.255.25414.121.255.25516,382
10514.122.0.0/1814.122.0.1 to 14.122.63.25414.122.63.25516,382
10614.122.64.0/1814.122.64.1 to 14.122.127.25414.122.127.25516,382
10714.122.128.0/1814.122.128.1 to 14.122.191.25414.122.191.25516,382
10814.122.192.0/1814.122.192.1 to 14.122.255.25414.122.255.25516,382
10914.123.0.0/1814.123.0.1 to 14.123.63.25414.123.63.25516,382
11014.123.64.0/1814.123.64.1 to 14.123.127.25414.123.127.25516,382
11114.123.128.0/1814.123.128.1 to 14.123.191.25414.123.191.25516,382
11214.123.192.0/1814.123.192.1 to 14.123.255.25414.123.255.25516,382
11314.124.0.0/1814.124.0.1 to 14.124.63.25414.124.63.25516,382
11414.124.64.0/1814.124.64.1 to 14.124.127.25414.124.127.25516,382
11514.124.128.0/1814.124.128.1 to 14.124.191.25414.124.191.25516,382
11614.124.192.0/1814.124.192.1 to 14.124.255.25414.124.255.25516,382
11714.125.0.0/1814.125.0.1 to 14.125.63.25414.125.63.25516,382
11814.125.64.0/1814.125.64.1 to 14.125.127.25414.125.127.25516,382
11914.125.128.0/1814.125.128.1 to 14.125.191.25414.125.191.25516,382
12014.125.192.0/1814.125.192.1 to 14.125.255.25414.125.255.25516,382
12114.126.0.0/1814.126.0.1 to 14.126.63.25414.126.63.25516,382
12214.126.64.0/1814.126.64.1 to 14.126.127.25414.126.127.25516,382
12314.126.128.0/1814.126.128.1 to 14.126.191.25414.126.191.25516,382
12414.126.192.0/1814.126.192.1 to 14.126.255.25414.126.255.25516,382
12514.127.0.0/1814.127.0.1 to 14.127.63.25414.127.63.25516,382
12614.127.64.0/1814.127.64.1 to 14.127.127.25414.127.127.25516,382
12714.127.128.0/1814.127.128.1 to 14.127.191.25414.127.191.25516,382
12814.127.192.0/1814.127.192.1 to 14.127.255.25414.127.255.25516,382

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.