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.

Network149.72.0.0/14
Usable hosts262,142
Subnet mask255.252.0.0
Addresses262,144
Network address
149.72.0.0
Broadcast address
149.75.255.255
First usable
149.72.0.1
Last usable
149.75.255.254
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
B (default /16)
As numbers
Hex 95480000 · Integer 2504523776 to 2504785919
Reverse DNS zones
72.149.in-addr.arpa
73.149.in-addr.arpa
74.149.in-addr.arpa
75.149.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
Address10010101.01001000.00000000.00000000149.72.0.0
Subnet mask11111111.11111100.00000000.00000000255.252.0.0
Network10010101.01001000.00000000.00000000149.72.0.0
Broadcast10010101.01001011.11111111.11111111149.75.255.255
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)

149.72.0.0/14 makes 128 subnets of /21.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1149.72.0.0/21149.72.0.1 to 149.72.7.254149.72.7.2552,046
2149.72.8.0/21149.72.8.1 to 149.72.15.254149.72.15.2552,046
3149.72.16.0/21149.72.16.1 to 149.72.23.254149.72.23.2552,046
4149.72.24.0/21149.72.24.1 to 149.72.31.254149.72.31.2552,046
5149.72.32.0/21149.72.32.1 to 149.72.39.254149.72.39.2552,046
6149.72.40.0/21149.72.40.1 to 149.72.47.254149.72.47.2552,046
7149.72.48.0/21149.72.48.1 to 149.72.55.254149.72.55.2552,046
8149.72.56.0/21149.72.56.1 to 149.72.63.254149.72.63.2552,046
9149.72.64.0/21149.72.64.1 to 149.72.71.254149.72.71.2552,046
10149.72.72.0/21149.72.72.1 to 149.72.79.254149.72.79.2552,046
11149.72.80.0/21149.72.80.1 to 149.72.87.254149.72.87.2552,046
12149.72.88.0/21149.72.88.1 to 149.72.95.254149.72.95.2552,046
13149.72.96.0/21149.72.96.1 to 149.72.103.254149.72.103.2552,046
14149.72.104.0/21149.72.104.1 to 149.72.111.254149.72.111.2552,046
15149.72.112.0/21149.72.112.1 to 149.72.119.254149.72.119.2552,046
16149.72.120.0/21149.72.120.1 to 149.72.127.254149.72.127.2552,046
17149.72.128.0/21149.72.128.1 to 149.72.135.254149.72.135.2552,046
18149.72.136.0/21149.72.136.1 to 149.72.143.254149.72.143.2552,046
19149.72.144.0/21149.72.144.1 to 149.72.151.254149.72.151.2552,046
20149.72.152.0/21149.72.152.1 to 149.72.159.254149.72.159.2552,046
21149.72.160.0/21149.72.160.1 to 149.72.167.254149.72.167.2552,046
22149.72.168.0/21149.72.168.1 to 149.72.175.254149.72.175.2552,046
23149.72.176.0/21149.72.176.1 to 149.72.183.254149.72.183.2552,046
24149.72.184.0/21149.72.184.1 to 149.72.191.254149.72.191.2552,046
25149.72.192.0/21149.72.192.1 to 149.72.199.254149.72.199.2552,046
26149.72.200.0/21149.72.200.1 to 149.72.207.254149.72.207.2552,046
27149.72.208.0/21149.72.208.1 to 149.72.215.254149.72.215.2552,046
28149.72.216.0/21149.72.216.1 to 149.72.223.254149.72.223.2552,046
29149.72.224.0/21149.72.224.1 to 149.72.231.254149.72.231.2552,046
30149.72.232.0/21149.72.232.1 to 149.72.239.254149.72.239.2552,046
31149.72.240.0/21149.72.240.1 to 149.72.247.254149.72.247.2552,046
32149.72.248.0/21149.72.248.1 to 149.72.255.254149.72.255.2552,046
33149.73.0.0/21149.73.0.1 to 149.73.7.254149.73.7.2552,046
34149.73.8.0/21149.73.8.1 to 149.73.15.254149.73.15.2552,046
35149.73.16.0/21149.73.16.1 to 149.73.23.254149.73.23.2552,046
36149.73.24.0/21149.73.24.1 to 149.73.31.254149.73.31.2552,046
37149.73.32.0/21149.73.32.1 to 149.73.39.254149.73.39.2552,046
38149.73.40.0/21149.73.40.1 to 149.73.47.254149.73.47.2552,046
39149.73.48.0/21149.73.48.1 to 149.73.55.254149.73.55.2552,046
40149.73.56.0/21149.73.56.1 to 149.73.63.254149.73.63.2552,046
41149.73.64.0/21149.73.64.1 to 149.73.71.254149.73.71.2552,046
42149.73.72.0/21149.73.72.1 to 149.73.79.254149.73.79.2552,046
43149.73.80.0/21149.73.80.1 to 149.73.87.254149.73.87.2552,046
44149.73.88.0/21149.73.88.1 to 149.73.95.254149.73.95.2552,046
45149.73.96.0/21149.73.96.1 to 149.73.103.254149.73.103.2552,046
46149.73.104.0/21149.73.104.1 to 149.73.111.254149.73.111.2552,046
47149.73.112.0/21149.73.112.1 to 149.73.119.254149.73.119.2552,046
48149.73.120.0/21149.73.120.1 to 149.73.127.254149.73.127.2552,046
49149.73.128.0/21149.73.128.1 to 149.73.135.254149.73.135.2552,046
50149.73.136.0/21149.73.136.1 to 149.73.143.254149.73.143.2552,046
51149.73.144.0/21149.73.144.1 to 149.73.151.254149.73.151.2552,046
52149.73.152.0/21149.73.152.1 to 149.73.159.254149.73.159.2552,046
53149.73.160.0/21149.73.160.1 to 149.73.167.254149.73.167.2552,046
54149.73.168.0/21149.73.168.1 to 149.73.175.254149.73.175.2552,046
55149.73.176.0/21149.73.176.1 to 149.73.183.254149.73.183.2552,046
56149.73.184.0/21149.73.184.1 to 149.73.191.254149.73.191.2552,046
57149.73.192.0/21149.73.192.1 to 149.73.199.254149.73.199.2552,046
58149.73.200.0/21149.73.200.1 to 149.73.207.254149.73.207.2552,046
59149.73.208.0/21149.73.208.1 to 149.73.215.254149.73.215.2552,046
60149.73.216.0/21149.73.216.1 to 149.73.223.254149.73.223.2552,046
61149.73.224.0/21149.73.224.1 to 149.73.231.254149.73.231.2552,046
62149.73.232.0/21149.73.232.1 to 149.73.239.254149.73.239.2552,046
63149.73.240.0/21149.73.240.1 to 149.73.247.254149.73.247.2552,046
64149.73.248.0/21149.73.248.1 to 149.73.255.254149.73.255.2552,046
65149.74.0.0/21149.74.0.1 to 149.74.7.254149.74.7.2552,046
66149.74.8.0/21149.74.8.1 to 149.74.15.254149.74.15.2552,046
67149.74.16.0/21149.74.16.1 to 149.74.23.254149.74.23.2552,046
68149.74.24.0/21149.74.24.1 to 149.74.31.254149.74.31.2552,046
69149.74.32.0/21149.74.32.1 to 149.74.39.254149.74.39.2552,046
70149.74.40.0/21149.74.40.1 to 149.74.47.254149.74.47.2552,046
71149.74.48.0/21149.74.48.1 to 149.74.55.254149.74.55.2552,046
72149.74.56.0/21149.74.56.1 to 149.74.63.254149.74.63.2552,046
73149.74.64.0/21149.74.64.1 to 149.74.71.254149.74.71.2552,046
74149.74.72.0/21149.74.72.1 to 149.74.79.254149.74.79.2552,046
75149.74.80.0/21149.74.80.1 to 149.74.87.254149.74.87.2552,046
76149.74.88.0/21149.74.88.1 to 149.74.95.254149.74.95.2552,046
77149.74.96.0/21149.74.96.1 to 149.74.103.254149.74.103.2552,046
78149.74.104.0/21149.74.104.1 to 149.74.111.254149.74.111.2552,046
79149.74.112.0/21149.74.112.1 to 149.74.119.254149.74.119.2552,046
80149.74.120.0/21149.74.120.1 to 149.74.127.254149.74.127.2552,046
81149.74.128.0/21149.74.128.1 to 149.74.135.254149.74.135.2552,046
82149.74.136.0/21149.74.136.1 to 149.74.143.254149.74.143.2552,046
83149.74.144.0/21149.74.144.1 to 149.74.151.254149.74.151.2552,046
84149.74.152.0/21149.74.152.1 to 149.74.159.254149.74.159.2552,046
85149.74.160.0/21149.74.160.1 to 149.74.167.254149.74.167.2552,046
86149.74.168.0/21149.74.168.1 to 149.74.175.254149.74.175.2552,046
87149.74.176.0/21149.74.176.1 to 149.74.183.254149.74.183.2552,046
88149.74.184.0/21149.74.184.1 to 149.74.191.254149.74.191.2552,046
89149.74.192.0/21149.74.192.1 to 149.74.199.254149.74.199.2552,046
90149.74.200.0/21149.74.200.1 to 149.74.207.254149.74.207.2552,046
91149.74.208.0/21149.74.208.1 to 149.74.215.254149.74.215.2552,046
92149.74.216.0/21149.74.216.1 to 149.74.223.254149.74.223.2552,046
93149.74.224.0/21149.74.224.1 to 149.74.231.254149.74.231.2552,046
94149.74.232.0/21149.74.232.1 to 149.74.239.254149.74.239.2552,046
95149.74.240.0/21149.74.240.1 to 149.74.247.254149.74.247.2552,046
96149.74.248.0/21149.74.248.1 to 149.74.255.254149.74.255.2552,046
97149.75.0.0/21149.75.0.1 to 149.75.7.254149.75.7.2552,046
98149.75.8.0/21149.75.8.1 to 149.75.15.254149.75.15.2552,046
99149.75.16.0/21149.75.16.1 to 149.75.23.254149.75.23.2552,046
100149.75.24.0/21149.75.24.1 to 149.75.31.254149.75.31.2552,046
101149.75.32.0/21149.75.32.1 to 149.75.39.254149.75.39.2552,046
102149.75.40.0/21149.75.40.1 to 149.75.47.254149.75.47.2552,046
103149.75.48.0/21149.75.48.1 to 149.75.55.254149.75.55.2552,046
104149.75.56.0/21149.75.56.1 to 149.75.63.254149.75.63.2552,046
105149.75.64.0/21149.75.64.1 to 149.75.71.254149.75.71.2552,046
106149.75.72.0/21149.75.72.1 to 149.75.79.254149.75.79.2552,046
107149.75.80.0/21149.75.80.1 to 149.75.87.254149.75.87.2552,046
108149.75.88.0/21149.75.88.1 to 149.75.95.254149.75.95.2552,046
109149.75.96.0/21149.75.96.1 to 149.75.103.254149.75.103.2552,046
110149.75.104.0/21149.75.104.1 to 149.75.111.254149.75.111.2552,046
111149.75.112.0/21149.75.112.1 to 149.75.119.254149.75.119.2552,046
112149.75.120.0/21149.75.120.1 to 149.75.127.254149.75.127.2552,046
113149.75.128.0/21149.75.128.1 to 149.75.135.254149.75.135.2552,046
114149.75.136.0/21149.75.136.1 to 149.75.143.254149.75.143.2552,046
115149.75.144.0/21149.75.144.1 to 149.75.151.254149.75.151.2552,046
116149.75.152.0/21149.75.152.1 to 149.75.159.254149.75.159.2552,046
117149.75.160.0/21149.75.160.1 to 149.75.167.254149.75.167.2552,046
118149.75.168.0/21149.75.168.1 to 149.75.175.254149.75.175.2552,046
119149.75.176.0/21149.75.176.1 to 149.75.183.254149.75.183.2552,046
120149.75.184.0/21149.75.184.1 to 149.75.191.254149.75.191.2552,046
121149.75.192.0/21149.75.192.1 to 149.75.199.254149.75.199.2552,046
122149.75.200.0/21149.75.200.1 to 149.75.207.254149.75.207.2552,046
123149.75.208.0/21149.75.208.1 to 149.75.215.254149.75.215.2552,046
124149.75.216.0/21149.75.216.1 to 149.75.223.254149.75.223.2552,046
125149.75.224.0/21149.75.224.1 to 149.75.231.254149.75.231.2552,046
126149.75.232.0/21149.75.232.1 to 149.75.239.254149.75.239.2552,046
127149.75.240.0/21149.75.240.1 to 149.75.247.254149.75.247.2552,046
128149.75.248.0/21149.75.248.1 to 149.75.255.254149.75.255.2552,046

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.