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.

Network167.167.96.0/19
Usable hosts8,190
Subnet mask255.255.224.0
Addresses8,192
Network address
167.167.96.0
Broadcast address
167.167.127.255
First usable
167.167.96.1
Last usable
167.167.127.254
Usable hosts
8,190 (8,192 less the network and broadcast addresses)
Subnet mask
255.255.224.0
Wildcard mask
0.0.31.255 (Cisco ACLs, OSPF)
Prefix length
/19
Type
Public public
Old class
B (default /16)
As numbers
Hex A7A76000 · Integer 2812764160 to 2812772351
Reverse DNS zones
96.167.167.in-addr.arpa
97.167.167.in-addr.arpa
98.167.167.in-addr.arpa
99.167.167.in-addr.arpa
100.167.167.in-addr.arpa
101.167.167.in-addr.arpa
102.167.167.in-addr.arpa
103.167.167.in-addr.arpa
104.167.167.in-addr.arpa
105.167.167.in-addr.arpa
106.167.167.in-addr.arpa
107.167.167.in-addr.arpa
108.167.167.in-addr.arpa
109.167.167.in-addr.arpa
110.167.167.in-addr.arpa
111.167.167.in-addr.arpa
and 16 more
/19 is not on a 8-bit boundary, so it takes 32 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10100111.10100111.01100000.00000000167.167.96.0
Subnet mask11111111.11111111.11100000.00000000255.255.224.0
Network10100111.10100111.01100000.00000000167.167.96.0
Broadcast10100111.10100111.01111111.11111111167.167.127.255
Split into smaller subnets/26
/20 (2)/21 (4)/22 (8)/23 (16)/24 (32)/25 (64)/26 (128)/27 (256)/28 (512)/29 (1,024)/30 (2,048)/31 (4,096)

167.167.96.0/19 makes 128 subnets of /26.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1167.167.96.0/26167.167.96.1 to 167.167.96.62167.167.96.6362
2167.167.96.64/26167.167.96.65 to 167.167.96.126167.167.96.12762
3167.167.96.128/26167.167.96.129 to 167.167.96.190167.167.96.19162
4167.167.96.192/26167.167.96.193 to 167.167.96.254167.167.96.25562
5167.167.97.0/26167.167.97.1 to 167.167.97.62167.167.97.6362
6167.167.97.64/26167.167.97.65 to 167.167.97.126167.167.97.12762
7167.167.97.128/26167.167.97.129 to 167.167.97.190167.167.97.19162
8167.167.97.192/26167.167.97.193 to 167.167.97.254167.167.97.25562
9167.167.98.0/26167.167.98.1 to 167.167.98.62167.167.98.6362
10167.167.98.64/26167.167.98.65 to 167.167.98.126167.167.98.12762
11167.167.98.128/26167.167.98.129 to 167.167.98.190167.167.98.19162
12167.167.98.192/26167.167.98.193 to 167.167.98.254167.167.98.25562
13167.167.99.0/26167.167.99.1 to 167.167.99.62167.167.99.6362
14167.167.99.64/26167.167.99.65 to 167.167.99.126167.167.99.12762
15167.167.99.128/26167.167.99.129 to 167.167.99.190167.167.99.19162
16167.167.99.192/26167.167.99.193 to 167.167.99.254167.167.99.25562
17167.167.100.0/26167.167.100.1 to 167.167.100.62167.167.100.6362
18167.167.100.64/26167.167.100.65 to 167.167.100.126167.167.100.12762
19167.167.100.128/26167.167.100.129 to 167.167.100.190167.167.100.19162
20167.167.100.192/26167.167.100.193 to 167.167.100.254167.167.100.25562
21167.167.101.0/26167.167.101.1 to 167.167.101.62167.167.101.6362
22167.167.101.64/26167.167.101.65 to 167.167.101.126167.167.101.12762
23167.167.101.128/26167.167.101.129 to 167.167.101.190167.167.101.19162
24167.167.101.192/26167.167.101.193 to 167.167.101.254167.167.101.25562
25167.167.102.0/26167.167.102.1 to 167.167.102.62167.167.102.6362
26167.167.102.64/26167.167.102.65 to 167.167.102.126167.167.102.12762
27167.167.102.128/26167.167.102.129 to 167.167.102.190167.167.102.19162
28167.167.102.192/26167.167.102.193 to 167.167.102.254167.167.102.25562
29167.167.103.0/26167.167.103.1 to 167.167.103.62167.167.103.6362
30167.167.103.64/26167.167.103.65 to 167.167.103.126167.167.103.12762
31167.167.103.128/26167.167.103.129 to 167.167.103.190167.167.103.19162
32167.167.103.192/26167.167.103.193 to 167.167.103.254167.167.103.25562
33167.167.104.0/26167.167.104.1 to 167.167.104.62167.167.104.6362
34167.167.104.64/26167.167.104.65 to 167.167.104.126167.167.104.12762
35167.167.104.128/26167.167.104.129 to 167.167.104.190167.167.104.19162
36167.167.104.192/26167.167.104.193 to 167.167.104.254167.167.104.25562
37167.167.105.0/26167.167.105.1 to 167.167.105.62167.167.105.6362
38167.167.105.64/26167.167.105.65 to 167.167.105.126167.167.105.12762
39167.167.105.128/26167.167.105.129 to 167.167.105.190167.167.105.19162
40167.167.105.192/26167.167.105.193 to 167.167.105.254167.167.105.25562
41167.167.106.0/26167.167.106.1 to 167.167.106.62167.167.106.6362
42167.167.106.64/26167.167.106.65 to 167.167.106.126167.167.106.12762
43167.167.106.128/26167.167.106.129 to 167.167.106.190167.167.106.19162
44167.167.106.192/26167.167.106.193 to 167.167.106.254167.167.106.25562
45167.167.107.0/26167.167.107.1 to 167.167.107.62167.167.107.6362
46167.167.107.64/26167.167.107.65 to 167.167.107.126167.167.107.12762
47167.167.107.128/26167.167.107.129 to 167.167.107.190167.167.107.19162
48167.167.107.192/26167.167.107.193 to 167.167.107.254167.167.107.25562
49167.167.108.0/26167.167.108.1 to 167.167.108.62167.167.108.6362
50167.167.108.64/26167.167.108.65 to 167.167.108.126167.167.108.12762
51167.167.108.128/26167.167.108.129 to 167.167.108.190167.167.108.19162
52167.167.108.192/26167.167.108.193 to 167.167.108.254167.167.108.25562
53167.167.109.0/26167.167.109.1 to 167.167.109.62167.167.109.6362
54167.167.109.64/26167.167.109.65 to 167.167.109.126167.167.109.12762
55167.167.109.128/26167.167.109.129 to 167.167.109.190167.167.109.19162
56167.167.109.192/26167.167.109.193 to 167.167.109.254167.167.109.25562
57167.167.110.0/26167.167.110.1 to 167.167.110.62167.167.110.6362
58167.167.110.64/26167.167.110.65 to 167.167.110.126167.167.110.12762
59167.167.110.128/26167.167.110.129 to 167.167.110.190167.167.110.19162
60167.167.110.192/26167.167.110.193 to 167.167.110.254167.167.110.25562
61167.167.111.0/26167.167.111.1 to 167.167.111.62167.167.111.6362
62167.167.111.64/26167.167.111.65 to 167.167.111.126167.167.111.12762
63167.167.111.128/26167.167.111.129 to 167.167.111.190167.167.111.19162
64167.167.111.192/26167.167.111.193 to 167.167.111.254167.167.111.25562
65167.167.112.0/26167.167.112.1 to 167.167.112.62167.167.112.6362
66167.167.112.64/26167.167.112.65 to 167.167.112.126167.167.112.12762
67167.167.112.128/26167.167.112.129 to 167.167.112.190167.167.112.19162
68167.167.112.192/26167.167.112.193 to 167.167.112.254167.167.112.25562
69167.167.113.0/26167.167.113.1 to 167.167.113.62167.167.113.6362
70167.167.113.64/26167.167.113.65 to 167.167.113.126167.167.113.12762
71167.167.113.128/26167.167.113.129 to 167.167.113.190167.167.113.19162
72167.167.113.192/26167.167.113.193 to 167.167.113.254167.167.113.25562
73167.167.114.0/26167.167.114.1 to 167.167.114.62167.167.114.6362
74167.167.114.64/26167.167.114.65 to 167.167.114.126167.167.114.12762
75167.167.114.128/26167.167.114.129 to 167.167.114.190167.167.114.19162
76167.167.114.192/26167.167.114.193 to 167.167.114.254167.167.114.25562
77167.167.115.0/26167.167.115.1 to 167.167.115.62167.167.115.6362
78167.167.115.64/26167.167.115.65 to 167.167.115.126167.167.115.12762
79167.167.115.128/26167.167.115.129 to 167.167.115.190167.167.115.19162
80167.167.115.192/26167.167.115.193 to 167.167.115.254167.167.115.25562
81167.167.116.0/26167.167.116.1 to 167.167.116.62167.167.116.6362
82167.167.116.64/26167.167.116.65 to 167.167.116.126167.167.116.12762
83167.167.116.128/26167.167.116.129 to 167.167.116.190167.167.116.19162
84167.167.116.192/26167.167.116.193 to 167.167.116.254167.167.116.25562
85167.167.117.0/26167.167.117.1 to 167.167.117.62167.167.117.6362
86167.167.117.64/26167.167.117.65 to 167.167.117.126167.167.117.12762
87167.167.117.128/26167.167.117.129 to 167.167.117.190167.167.117.19162
88167.167.117.192/26167.167.117.193 to 167.167.117.254167.167.117.25562
89167.167.118.0/26167.167.118.1 to 167.167.118.62167.167.118.6362
90167.167.118.64/26167.167.118.65 to 167.167.118.126167.167.118.12762
91167.167.118.128/26167.167.118.129 to 167.167.118.190167.167.118.19162
92167.167.118.192/26167.167.118.193 to 167.167.118.254167.167.118.25562
93167.167.119.0/26167.167.119.1 to 167.167.119.62167.167.119.6362
94167.167.119.64/26167.167.119.65 to 167.167.119.126167.167.119.12762
95167.167.119.128/26167.167.119.129 to 167.167.119.190167.167.119.19162
96167.167.119.192/26167.167.119.193 to 167.167.119.254167.167.119.25562
97167.167.120.0/26167.167.120.1 to 167.167.120.62167.167.120.6362
98167.167.120.64/26167.167.120.65 to 167.167.120.126167.167.120.12762
99167.167.120.128/26167.167.120.129 to 167.167.120.190167.167.120.19162
100167.167.120.192/26167.167.120.193 to 167.167.120.254167.167.120.25562
101167.167.121.0/26167.167.121.1 to 167.167.121.62167.167.121.6362
102167.167.121.64/26167.167.121.65 to 167.167.121.126167.167.121.12762
103167.167.121.128/26167.167.121.129 to 167.167.121.190167.167.121.19162
104167.167.121.192/26167.167.121.193 to 167.167.121.254167.167.121.25562
105167.167.122.0/26167.167.122.1 to 167.167.122.62167.167.122.6362
106167.167.122.64/26167.167.122.65 to 167.167.122.126167.167.122.12762
107167.167.122.128/26167.167.122.129 to 167.167.122.190167.167.122.19162
108167.167.122.192/26167.167.122.193 to 167.167.122.254167.167.122.25562
109167.167.123.0/26167.167.123.1 to 167.167.123.62167.167.123.6362
110167.167.123.64/26167.167.123.65 to 167.167.123.126167.167.123.12762
111167.167.123.128/26167.167.123.129 to 167.167.123.190167.167.123.19162
112167.167.123.192/26167.167.123.193 to 167.167.123.254167.167.123.25562
113167.167.124.0/26167.167.124.1 to 167.167.124.62167.167.124.6362
114167.167.124.64/26167.167.124.65 to 167.167.124.126167.167.124.12762
115167.167.124.128/26167.167.124.129 to 167.167.124.190167.167.124.19162
116167.167.124.192/26167.167.124.193 to 167.167.124.254167.167.124.25562
117167.167.125.0/26167.167.125.1 to 167.167.125.62167.167.125.6362
118167.167.125.64/26167.167.125.65 to 167.167.125.126167.167.125.12762
119167.167.125.128/26167.167.125.129 to 167.167.125.190167.167.125.19162
120167.167.125.192/26167.167.125.193 to 167.167.125.254167.167.125.25562
121167.167.126.0/26167.167.126.1 to 167.167.126.62167.167.126.6362
122167.167.126.64/26167.167.126.65 to 167.167.126.126167.167.126.12762
123167.167.126.128/26167.167.126.129 to 167.167.126.190167.167.126.19162
124167.167.126.192/26167.167.126.193 to 167.167.126.254167.167.126.25562
125167.167.127.0/26167.167.127.1 to 167.167.127.62167.167.127.6362
126167.167.127.64/26167.167.127.65 to 167.167.127.126167.167.127.12762
127167.167.127.128/26167.167.127.129 to 167.167.127.190167.167.127.19162
128167.167.127.192/26167.167.127.193 to 167.167.127.254167.167.127.25562

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.