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.

Network149.52.0.0/15
Usable hosts131,070
Subnet mask255.254.0.0
Addresses131,072
Network address
149.52.0.0
Broadcast address
149.53.255.255
First usable
149.52.0.1
Last usable
149.53.255.254
Usable hosts
131,070 (131,072 less the network and broadcast addresses)
Subnet mask
255.254.0.0
Wildcard mask
0.1.255.255 (Cisco ACLs, OSPF)
Prefix length
/15
Type
Public public
Old class
B (default /16)
As numbers
Hex 95340000 · Integer 2503213056 to 2503344127
Reverse DNS zones
52.149.in-addr.arpa
53.149.in-addr.arpa
/15 is not on a 8-bit boundary, so it takes 2 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10010101.00110100.00000000.00000000149.52.0.0
Subnet mask11111111.11111110.00000000.00000000255.254.0.0
Network10010101.00110100.00000000.00000000149.52.0.0
Broadcast10010101.00110101.11111111.11111111149.53.255.255
Split into smaller subnets/22
/16 (2)/17 (4)/18 (8)/19 (16)/20 (32)/21 (64)/22 (128)/23 (256)/24 (512)/25 (1,024)/26 (2,048)/27 (4,096)

149.52.0.0/15 makes 128 subnets of /22.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1149.52.0.0/22149.52.0.1 to 149.52.3.254149.52.3.2551,022
2149.52.4.0/22149.52.4.1 to 149.52.7.254149.52.7.2551,022
3149.52.8.0/22149.52.8.1 to 149.52.11.254149.52.11.2551,022
4149.52.12.0/22149.52.12.1 to 149.52.15.254149.52.15.2551,022
5149.52.16.0/22149.52.16.1 to 149.52.19.254149.52.19.2551,022
6149.52.20.0/22149.52.20.1 to 149.52.23.254149.52.23.2551,022
7149.52.24.0/22149.52.24.1 to 149.52.27.254149.52.27.2551,022
8149.52.28.0/22149.52.28.1 to 149.52.31.254149.52.31.2551,022
9149.52.32.0/22149.52.32.1 to 149.52.35.254149.52.35.2551,022
10149.52.36.0/22149.52.36.1 to 149.52.39.254149.52.39.2551,022
11149.52.40.0/22149.52.40.1 to 149.52.43.254149.52.43.2551,022
12149.52.44.0/22149.52.44.1 to 149.52.47.254149.52.47.2551,022
13149.52.48.0/22149.52.48.1 to 149.52.51.254149.52.51.2551,022
14149.52.52.0/22149.52.52.1 to 149.52.55.254149.52.55.2551,022
15149.52.56.0/22149.52.56.1 to 149.52.59.254149.52.59.2551,022
16149.52.60.0/22149.52.60.1 to 149.52.63.254149.52.63.2551,022
17149.52.64.0/22149.52.64.1 to 149.52.67.254149.52.67.2551,022
18149.52.68.0/22149.52.68.1 to 149.52.71.254149.52.71.2551,022
19149.52.72.0/22149.52.72.1 to 149.52.75.254149.52.75.2551,022
20149.52.76.0/22149.52.76.1 to 149.52.79.254149.52.79.2551,022
21149.52.80.0/22149.52.80.1 to 149.52.83.254149.52.83.2551,022
22149.52.84.0/22149.52.84.1 to 149.52.87.254149.52.87.2551,022
23149.52.88.0/22149.52.88.1 to 149.52.91.254149.52.91.2551,022
24149.52.92.0/22149.52.92.1 to 149.52.95.254149.52.95.2551,022
25149.52.96.0/22149.52.96.1 to 149.52.99.254149.52.99.2551,022
26149.52.100.0/22149.52.100.1 to 149.52.103.254149.52.103.2551,022
27149.52.104.0/22149.52.104.1 to 149.52.107.254149.52.107.2551,022
28149.52.108.0/22149.52.108.1 to 149.52.111.254149.52.111.2551,022
29149.52.112.0/22149.52.112.1 to 149.52.115.254149.52.115.2551,022
30149.52.116.0/22149.52.116.1 to 149.52.119.254149.52.119.2551,022
31149.52.120.0/22149.52.120.1 to 149.52.123.254149.52.123.2551,022
32149.52.124.0/22149.52.124.1 to 149.52.127.254149.52.127.2551,022
33149.52.128.0/22149.52.128.1 to 149.52.131.254149.52.131.2551,022
34149.52.132.0/22149.52.132.1 to 149.52.135.254149.52.135.2551,022
35149.52.136.0/22149.52.136.1 to 149.52.139.254149.52.139.2551,022
36149.52.140.0/22149.52.140.1 to 149.52.143.254149.52.143.2551,022
37149.52.144.0/22149.52.144.1 to 149.52.147.254149.52.147.2551,022
38149.52.148.0/22149.52.148.1 to 149.52.151.254149.52.151.2551,022
39149.52.152.0/22149.52.152.1 to 149.52.155.254149.52.155.2551,022
40149.52.156.0/22149.52.156.1 to 149.52.159.254149.52.159.2551,022
41149.52.160.0/22149.52.160.1 to 149.52.163.254149.52.163.2551,022
42149.52.164.0/22149.52.164.1 to 149.52.167.254149.52.167.2551,022
43149.52.168.0/22149.52.168.1 to 149.52.171.254149.52.171.2551,022
44149.52.172.0/22149.52.172.1 to 149.52.175.254149.52.175.2551,022
45149.52.176.0/22149.52.176.1 to 149.52.179.254149.52.179.2551,022
46149.52.180.0/22149.52.180.1 to 149.52.183.254149.52.183.2551,022
47149.52.184.0/22149.52.184.1 to 149.52.187.254149.52.187.2551,022
48149.52.188.0/22149.52.188.1 to 149.52.191.254149.52.191.2551,022
49149.52.192.0/22149.52.192.1 to 149.52.195.254149.52.195.2551,022
50149.52.196.0/22149.52.196.1 to 149.52.199.254149.52.199.2551,022
51149.52.200.0/22149.52.200.1 to 149.52.203.254149.52.203.2551,022
52149.52.204.0/22149.52.204.1 to 149.52.207.254149.52.207.2551,022
53149.52.208.0/22149.52.208.1 to 149.52.211.254149.52.211.2551,022
54149.52.212.0/22149.52.212.1 to 149.52.215.254149.52.215.2551,022
55149.52.216.0/22149.52.216.1 to 149.52.219.254149.52.219.2551,022
56149.52.220.0/22149.52.220.1 to 149.52.223.254149.52.223.2551,022
57149.52.224.0/22149.52.224.1 to 149.52.227.254149.52.227.2551,022
58149.52.228.0/22149.52.228.1 to 149.52.231.254149.52.231.2551,022
59149.52.232.0/22149.52.232.1 to 149.52.235.254149.52.235.2551,022
60149.52.236.0/22149.52.236.1 to 149.52.239.254149.52.239.2551,022
61149.52.240.0/22149.52.240.1 to 149.52.243.254149.52.243.2551,022
62149.52.244.0/22149.52.244.1 to 149.52.247.254149.52.247.2551,022
63149.52.248.0/22149.52.248.1 to 149.52.251.254149.52.251.2551,022
64149.52.252.0/22149.52.252.1 to 149.52.255.254149.52.255.2551,022
65149.53.0.0/22149.53.0.1 to 149.53.3.254149.53.3.2551,022
66149.53.4.0/22149.53.4.1 to 149.53.7.254149.53.7.2551,022
67149.53.8.0/22149.53.8.1 to 149.53.11.254149.53.11.2551,022
68149.53.12.0/22149.53.12.1 to 149.53.15.254149.53.15.2551,022
69149.53.16.0/22149.53.16.1 to 149.53.19.254149.53.19.2551,022
70149.53.20.0/22149.53.20.1 to 149.53.23.254149.53.23.2551,022
71149.53.24.0/22149.53.24.1 to 149.53.27.254149.53.27.2551,022
72149.53.28.0/22149.53.28.1 to 149.53.31.254149.53.31.2551,022
73149.53.32.0/22149.53.32.1 to 149.53.35.254149.53.35.2551,022
74149.53.36.0/22149.53.36.1 to 149.53.39.254149.53.39.2551,022
75149.53.40.0/22149.53.40.1 to 149.53.43.254149.53.43.2551,022
76149.53.44.0/22149.53.44.1 to 149.53.47.254149.53.47.2551,022
77149.53.48.0/22149.53.48.1 to 149.53.51.254149.53.51.2551,022
78149.53.52.0/22149.53.52.1 to 149.53.55.254149.53.55.2551,022
79149.53.56.0/22149.53.56.1 to 149.53.59.254149.53.59.2551,022
80149.53.60.0/22149.53.60.1 to 149.53.63.254149.53.63.2551,022
81149.53.64.0/22149.53.64.1 to 149.53.67.254149.53.67.2551,022
82149.53.68.0/22149.53.68.1 to 149.53.71.254149.53.71.2551,022
83149.53.72.0/22149.53.72.1 to 149.53.75.254149.53.75.2551,022
84149.53.76.0/22149.53.76.1 to 149.53.79.254149.53.79.2551,022
85149.53.80.0/22149.53.80.1 to 149.53.83.254149.53.83.2551,022
86149.53.84.0/22149.53.84.1 to 149.53.87.254149.53.87.2551,022
87149.53.88.0/22149.53.88.1 to 149.53.91.254149.53.91.2551,022
88149.53.92.0/22149.53.92.1 to 149.53.95.254149.53.95.2551,022
89149.53.96.0/22149.53.96.1 to 149.53.99.254149.53.99.2551,022
90149.53.100.0/22149.53.100.1 to 149.53.103.254149.53.103.2551,022
91149.53.104.0/22149.53.104.1 to 149.53.107.254149.53.107.2551,022
92149.53.108.0/22149.53.108.1 to 149.53.111.254149.53.111.2551,022
93149.53.112.0/22149.53.112.1 to 149.53.115.254149.53.115.2551,022
94149.53.116.0/22149.53.116.1 to 149.53.119.254149.53.119.2551,022
95149.53.120.0/22149.53.120.1 to 149.53.123.254149.53.123.2551,022
96149.53.124.0/22149.53.124.1 to 149.53.127.254149.53.127.2551,022
97149.53.128.0/22149.53.128.1 to 149.53.131.254149.53.131.2551,022
98149.53.132.0/22149.53.132.1 to 149.53.135.254149.53.135.2551,022
99149.53.136.0/22149.53.136.1 to 149.53.139.254149.53.139.2551,022
100149.53.140.0/22149.53.140.1 to 149.53.143.254149.53.143.2551,022
101149.53.144.0/22149.53.144.1 to 149.53.147.254149.53.147.2551,022
102149.53.148.0/22149.53.148.1 to 149.53.151.254149.53.151.2551,022
103149.53.152.0/22149.53.152.1 to 149.53.155.254149.53.155.2551,022
104149.53.156.0/22149.53.156.1 to 149.53.159.254149.53.159.2551,022
105149.53.160.0/22149.53.160.1 to 149.53.163.254149.53.163.2551,022
106149.53.164.0/22149.53.164.1 to 149.53.167.254149.53.167.2551,022
107149.53.168.0/22149.53.168.1 to 149.53.171.254149.53.171.2551,022
108149.53.172.0/22149.53.172.1 to 149.53.175.254149.53.175.2551,022
109149.53.176.0/22149.53.176.1 to 149.53.179.254149.53.179.2551,022
110149.53.180.0/22149.53.180.1 to 149.53.183.254149.53.183.2551,022
111149.53.184.0/22149.53.184.1 to 149.53.187.254149.53.187.2551,022
112149.53.188.0/22149.53.188.1 to 149.53.191.254149.53.191.2551,022
113149.53.192.0/22149.53.192.1 to 149.53.195.254149.53.195.2551,022
114149.53.196.0/22149.53.196.1 to 149.53.199.254149.53.199.2551,022
115149.53.200.0/22149.53.200.1 to 149.53.203.254149.53.203.2551,022
116149.53.204.0/22149.53.204.1 to 149.53.207.254149.53.207.2551,022
117149.53.208.0/22149.53.208.1 to 149.53.211.254149.53.211.2551,022
118149.53.212.0/22149.53.212.1 to 149.53.215.254149.53.215.2551,022
119149.53.216.0/22149.53.216.1 to 149.53.219.254149.53.219.2551,022
120149.53.220.0/22149.53.220.1 to 149.53.223.254149.53.223.2551,022
121149.53.224.0/22149.53.224.1 to 149.53.227.254149.53.227.2551,022
122149.53.228.0/22149.53.228.1 to 149.53.231.254149.53.231.2551,022
123149.53.232.0/22149.53.232.1 to 149.53.235.254149.53.235.2551,022
124149.53.236.0/22149.53.236.1 to 149.53.239.254149.53.239.2551,022
125149.53.240.0/22149.53.240.1 to 149.53.243.254149.53.243.2551,022
126149.53.244.0/22149.53.244.1 to 149.53.247.254149.53.247.2551,022
127149.53.248.0/22149.53.248.1 to 149.53.251.254149.53.251.2551,022
128149.53.252.0/22149.53.252.1 to 149.53.255.254149.53.255.2551,022

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.