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.

Network174.0.0.0/9
Usable hosts8,388,606
Subnet mask255.128.0.0
Addresses8,388,608
Network address
174.0.0.0
Broadcast address
174.127.255.255
First usable
174.0.0.1
Last usable
174.127.255.254
Usable hosts
8,388,606 (8,388,608 less the network and broadcast addresses)
Subnet mask
255.128.0.0
Wildcard mask
0.127.255.255 (Cisco ACLs, OSPF)
Prefix length
/9
Type
Public public
Old class
B (default /16)
As numbers
Hex AE000000 · Integer 2919235584 to 2927624191
Reverse DNS zones
0.174.in-addr.arpa
1.174.in-addr.arpa
2.174.in-addr.arpa
3.174.in-addr.arpa
4.174.in-addr.arpa
5.174.in-addr.arpa
6.174.in-addr.arpa
7.174.in-addr.arpa
8.174.in-addr.arpa
9.174.in-addr.arpa
10.174.in-addr.arpa
11.174.in-addr.arpa
12.174.in-addr.arpa
13.174.in-addr.arpa
14.174.in-addr.arpa
15.174.in-addr.arpa
and 112 more
/9 is not on a 8-bit boundary, so it takes 128 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10101110.00000000.00000000.00000000174.0.0.0
Subnet mask11111111.10000000.00000000.00000000255.128.0.0
Network10101110.00000000.00000000.00000000174.0.0.0
Broadcast10101110.01111111.11111111.11111111174.127.255.255
Split into smaller subnets/16
/10 (2)/11 (4)/12 (8)/13 (16)/14 (32)/15 (64)/16 (128)/17 (256)/18 (512)/19 (1,024)/20 (2,048)/21 (4,096)

174.0.0.0/9 makes 128 subnets of /16.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1174.0.0.0/16174.0.0.1 to 174.0.255.254174.0.255.25565,534
2174.1.0.0/16174.1.0.1 to 174.1.255.254174.1.255.25565,534
3174.2.0.0/16174.2.0.1 to 174.2.255.254174.2.255.25565,534
4174.3.0.0/16174.3.0.1 to 174.3.255.254174.3.255.25565,534
5174.4.0.0/16174.4.0.1 to 174.4.255.254174.4.255.25565,534
6174.5.0.0/16174.5.0.1 to 174.5.255.254174.5.255.25565,534
7174.6.0.0/16174.6.0.1 to 174.6.255.254174.6.255.25565,534
8174.7.0.0/16174.7.0.1 to 174.7.255.254174.7.255.25565,534
9174.8.0.0/16174.8.0.1 to 174.8.255.254174.8.255.25565,534
10174.9.0.0/16174.9.0.1 to 174.9.255.254174.9.255.25565,534
11174.10.0.0/16174.10.0.1 to 174.10.255.254174.10.255.25565,534
12174.11.0.0/16174.11.0.1 to 174.11.255.254174.11.255.25565,534
13174.12.0.0/16174.12.0.1 to 174.12.255.254174.12.255.25565,534
14174.13.0.0/16174.13.0.1 to 174.13.255.254174.13.255.25565,534
15174.14.0.0/16174.14.0.1 to 174.14.255.254174.14.255.25565,534
16174.15.0.0/16174.15.0.1 to 174.15.255.254174.15.255.25565,534
17174.16.0.0/16174.16.0.1 to 174.16.255.254174.16.255.25565,534
18174.17.0.0/16174.17.0.1 to 174.17.255.254174.17.255.25565,534
19174.18.0.0/16174.18.0.1 to 174.18.255.254174.18.255.25565,534
20174.19.0.0/16174.19.0.1 to 174.19.255.254174.19.255.25565,534
21174.20.0.0/16174.20.0.1 to 174.20.255.254174.20.255.25565,534
22174.21.0.0/16174.21.0.1 to 174.21.255.254174.21.255.25565,534
23174.22.0.0/16174.22.0.1 to 174.22.255.254174.22.255.25565,534
24174.23.0.0/16174.23.0.1 to 174.23.255.254174.23.255.25565,534
25174.24.0.0/16174.24.0.1 to 174.24.255.254174.24.255.25565,534
26174.25.0.0/16174.25.0.1 to 174.25.255.254174.25.255.25565,534
27174.26.0.0/16174.26.0.1 to 174.26.255.254174.26.255.25565,534
28174.27.0.0/16174.27.0.1 to 174.27.255.254174.27.255.25565,534
29174.28.0.0/16174.28.0.1 to 174.28.255.254174.28.255.25565,534
30174.29.0.0/16174.29.0.1 to 174.29.255.254174.29.255.25565,534
31174.30.0.0/16174.30.0.1 to 174.30.255.254174.30.255.25565,534
32174.31.0.0/16174.31.0.1 to 174.31.255.254174.31.255.25565,534
33174.32.0.0/16174.32.0.1 to 174.32.255.254174.32.255.25565,534
34174.33.0.0/16174.33.0.1 to 174.33.255.254174.33.255.25565,534
35174.34.0.0/16174.34.0.1 to 174.34.255.254174.34.255.25565,534
36174.35.0.0/16174.35.0.1 to 174.35.255.254174.35.255.25565,534
37174.36.0.0/16174.36.0.1 to 174.36.255.254174.36.255.25565,534
38174.37.0.0/16174.37.0.1 to 174.37.255.254174.37.255.25565,534
39174.38.0.0/16174.38.0.1 to 174.38.255.254174.38.255.25565,534
40174.39.0.0/16174.39.0.1 to 174.39.255.254174.39.255.25565,534
41174.40.0.0/16174.40.0.1 to 174.40.255.254174.40.255.25565,534
42174.41.0.0/16174.41.0.1 to 174.41.255.254174.41.255.25565,534
43174.42.0.0/16174.42.0.1 to 174.42.255.254174.42.255.25565,534
44174.43.0.0/16174.43.0.1 to 174.43.255.254174.43.255.25565,534
45174.44.0.0/16174.44.0.1 to 174.44.255.254174.44.255.25565,534
46174.45.0.0/16174.45.0.1 to 174.45.255.254174.45.255.25565,534
47174.46.0.0/16174.46.0.1 to 174.46.255.254174.46.255.25565,534
48174.47.0.0/16174.47.0.1 to 174.47.255.254174.47.255.25565,534
49174.48.0.0/16174.48.0.1 to 174.48.255.254174.48.255.25565,534
50174.49.0.0/16174.49.0.1 to 174.49.255.254174.49.255.25565,534
51174.50.0.0/16174.50.0.1 to 174.50.255.254174.50.255.25565,534
52174.51.0.0/16174.51.0.1 to 174.51.255.254174.51.255.25565,534
53174.52.0.0/16174.52.0.1 to 174.52.255.254174.52.255.25565,534
54174.53.0.0/16174.53.0.1 to 174.53.255.254174.53.255.25565,534
55174.54.0.0/16174.54.0.1 to 174.54.255.254174.54.255.25565,534
56174.55.0.0/16174.55.0.1 to 174.55.255.254174.55.255.25565,534
57174.56.0.0/16174.56.0.1 to 174.56.255.254174.56.255.25565,534
58174.57.0.0/16174.57.0.1 to 174.57.255.254174.57.255.25565,534
59174.58.0.0/16174.58.0.1 to 174.58.255.254174.58.255.25565,534
60174.59.0.0/16174.59.0.1 to 174.59.255.254174.59.255.25565,534
61174.60.0.0/16174.60.0.1 to 174.60.255.254174.60.255.25565,534
62174.61.0.0/16174.61.0.1 to 174.61.255.254174.61.255.25565,534
63174.62.0.0/16174.62.0.1 to 174.62.255.254174.62.255.25565,534
64174.63.0.0/16174.63.0.1 to 174.63.255.254174.63.255.25565,534
65174.64.0.0/16174.64.0.1 to 174.64.255.254174.64.255.25565,534
66174.65.0.0/16174.65.0.1 to 174.65.255.254174.65.255.25565,534
67174.66.0.0/16174.66.0.1 to 174.66.255.254174.66.255.25565,534
68174.67.0.0/16174.67.0.1 to 174.67.255.254174.67.255.25565,534
69174.68.0.0/16174.68.0.1 to 174.68.255.254174.68.255.25565,534
70174.69.0.0/16174.69.0.1 to 174.69.255.254174.69.255.25565,534
71174.70.0.0/16174.70.0.1 to 174.70.255.254174.70.255.25565,534
72174.71.0.0/16174.71.0.1 to 174.71.255.254174.71.255.25565,534
73174.72.0.0/16174.72.0.1 to 174.72.255.254174.72.255.25565,534
74174.73.0.0/16174.73.0.1 to 174.73.255.254174.73.255.25565,534
75174.74.0.0/16174.74.0.1 to 174.74.255.254174.74.255.25565,534
76174.75.0.0/16174.75.0.1 to 174.75.255.254174.75.255.25565,534
77174.76.0.0/16174.76.0.1 to 174.76.255.254174.76.255.25565,534
78174.77.0.0/16174.77.0.1 to 174.77.255.254174.77.255.25565,534
79174.78.0.0/16174.78.0.1 to 174.78.255.254174.78.255.25565,534
80174.79.0.0/16174.79.0.1 to 174.79.255.254174.79.255.25565,534
81174.80.0.0/16174.80.0.1 to 174.80.255.254174.80.255.25565,534
82174.81.0.0/16174.81.0.1 to 174.81.255.254174.81.255.25565,534
83174.82.0.0/16174.82.0.1 to 174.82.255.254174.82.255.25565,534
84174.83.0.0/16174.83.0.1 to 174.83.255.254174.83.255.25565,534
85174.84.0.0/16174.84.0.1 to 174.84.255.254174.84.255.25565,534
86174.85.0.0/16174.85.0.1 to 174.85.255.254174.85.255.25565,534
87174.86.0.0/16174.86.0.1 to 174.86.255.254174.86.255.25565,534
88174.87.0.0/16174.87.0.1 to 174.87.255.254174.87.255.25565,534
89174.88.0.0/16174.88.0.1 to 174.88.255.254174.88.255.25565,534
90174.89.0.0/16174.89.0.1 to 174.89.255.254174.89.255.25565,534
91174.90.0.0/16174.90.0.1 to 174.90.255.254174.90.255.25565,534
92174.91.0.0/16174.91.0.1 to 174.91.255.254174.91.255.25565,534
93174.92.0.0/16174.92.0.1 to 174.92.255.254174.92.255.25565,534
94174.93.0.0/16174.93.0.1 to 174.93.255.254174.93.255.25565,534
95174.94.0.0/16174.94.0.1 to 174.94.255.254174.94.255.25565,534
96174.95.0.0/16174.95.0.1 to 174.95.255.254174.95.255.25565,534
97174.96.0.0/16174.96.0.1 to 174.96.255.254174.96.255.25565,534
98174.97.0.0/16174.97.0.1 to 174.97.255.254174.97.255.25565,534
99174.98.0.0/16174.98.0.1 to 174.98.255.254174.98.255.25565,534
100174.99.0.0/16174.99.0.1 to 174.99.255.254174.99.255.25565,534
101174.100.0.0/16174.100.0.1 to 174.100.255.254174.100.255.25565,534
102174.101.0.0/16174.101.0.1 to 174.101.255.254174.101.255.25565,534
103174.102.0.0/16174.102.0.1 to 174.102.255.254174.102.255.25565,534
104174.103.0.0/16174.103.0.1 to 174.103.255.254174.103.255.25565,534
105174.104.0.0/16174.104.0.1 to 174.104.255.254174.104.255.25565,534
106174.105.0.0/16174.105.0.1 to 174.105.255.254174.105.255.25565,534
107174.106.0.0/16174.106.0.1 to 174.106.255.254174.106.255.25565,534
108174.107.0.0/16174.107.0.1 to 174.107.255.254174.107.255.25565,534
109174.108.0.0/16174.108.0.1 to 174.108.255.254174.108.255.25565,534
110174.109.0.0/16174.109.0.1 to 174.109.255.254174.109.255.25565,534
111174.110.0.0/16174.110.0.1 to 174.110.255.254174.110.255.25565,534
112174.111.0.0/16174.111.0.1 to 174.111.255.254174.111.255.25565,534
113174.112.0.0/16174.112.0.1 to 174.112.255.254174.112.255.25565,534
114174.113.0.0/16174.113.0.1 to 174.113.255.254174.113.255.25565,534
115174.114.0.0/16174.114.0.1 to 174.114.255.254174.114.255.25565,534
116174.115.0.0/16174.115.0.1 to 174.115.255.254174.115.255.25565,534
117174.116.0.0/16174.116.0.1 to 174.116.255.254174.116.255.25565,534
118174.117.0.0/16174.117.0.1 to 174.117.255.254174.117.255.25565,534
119174.118.0.0/16174.118.0.1 to 174.118.255.254174.118.255.25565,534
120174.119.0.0/16174.119.0.1 to 174.119.255.254174.119.255.25565,534
121174.120.0.0/16174.120.0.1 to 174.120.255.254174.120.255.25565,534
122174.121.0.0/16174.121.0.1 to 174.121.255.254174.121.255.25565,534
123174.122.0.0/16174.122.0.1 to 174.122.255.254174.122.255.25565,534
124174.123.0.0/16174.123.0.1 to 174.123.255.254174.123.255.25565,534
125174.124.0.0/16174.124.0.1 to 174.124.255.254174.124.255.25565,534
126174.125.0.0/16174.125.0.1 to 174.125.255.254174.125.255.25565,534
127174.126.0.0/16174.126.0.1 to 174.126.255.254174.126.255.25565,534
128174.127.0.0/16174.127.0.1 to 174.127.255.254174.127.255.25565,534

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.