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.

Network148.167.2.192/26
Usable hosts62
Subnet mask255.255.255.192
Addresses64
Network address
148.167.2.192
Broadcast address
148.167.2.255
First usable
148.167.2.193
Last usable
148.167.2.254
Usable hosts
62 (64 less the network and broadcast addresses)
Subnet mask
255.255.255.192
Wildcard mask
0.0.0.63 (Cisco ACLs, OSPF)
Prefix length
/26
Type
Public public
Old class
B (default /16)
As numbers
Hex 94A702C0 · Integer 2493973184 to 2493973247
Reverse DNS zone
2.167.148.in-addr.arpa
Smaller than a /24: the provider delegates it inside the /24 zone (RFC 2317), or sets each PTR record for you.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10010100.10100111.00000010.11000000148.167.2.192
Subnet mask11111111.11111111.11111111.11000000255.255.255.192
Network10010100.10100111.00000010.11000000148.167.2.192
Broadcast10010100.10100111.00000010.11111111148.167.2.255
Split into smaller subnets/32
/27 (2)/28 (4)/29 (8)/30 (16)/31 (32)/32 (64)

148.167.2.192/26 makes 64 subnets of /32.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1148.167.2.192/32148.167.2.192 to 148.167.2.192—1
2148.167.2.193/32148.167.2.193 to 148.167.2.193—1
3148.167.2.194/32148.167.2.194 to 148.167.2.194—1
4148.167.2.195/32148.167.2.195 to 148.167.2.195—1
5148.167.2.196/32148.167.2.196 to 148.167.2.196—1
6148.167.2.197/32148.167.2.197 to 148.167.2.197—1
7148.167.2.198/32148.167.2.198 to 148.167.2.198—1
8148.167.2.199/32148.167.2.199 to 148.167.2.199—1
9148.167.2.200/32148.167.2.200 to 148.167.2.200—1
10148.167.2.201/32148.167.2.201 to 148.167.2.201—1
11148.167.2.202/32148.167.2.202 to 148.167.2.202—1
12148.167.2.203/32148.167.2.203 to 148.167.2.203—1
13148.167.2.204/32148.167.2.204 to 148.167.2.204—1
14148.167.2.205/32148.167.2.205 to 148.167.2.205—1
15148.167.2.206/32148.167.2.206 to 148.167.2.206—1
16148.167.2.207/32148.167.2.207 to 148.167.2.207—1
17148.167.2.208/32148.167.2.208 to 148.167.2.208—1
18148.167.2.209/32148.167.2.209 to 148.167.2.209—1
19148.167.2.210/32148.167.2.210 to 148.167.2.210—1
20148.167.2.211/32148.167.2.211 to 148.167.2.211—1
21148.167.2.212/32148.167.2.212 to 148.167.2.212—1
22148.167.2.213/32148.167.2.213 to 148.167.2.213—1
23148.167.2.214/32148.167.2.214 to 148.167.2.214—1
24148.167.2.215/32148.167.2.215 to 148.167.2.215—1
25148.167.2.216/32148.167.2.216 to 148.167.2.216—1
26148.167.2.217/32148.167.2.217 to 148.167.2.217—1
27148.167.2.218/32148.167.2.218 to 148.167.2.218—1
28148.167.2.219/32148.167.2.219 to 148.167.2.219—1
29148.167.2.220/32148.167.2.220 to 148.167.2.220—1
30148.167.2.221/32148.167.2.221 to 148.167.2.221—1
31148.167.2.222/32148.167.2.222 to 148.167.2.222—1
32148.167.2.223/32148.167.2.223 to 148.167.2.223—1
33148.167.2.224/32148.167.2.224 to 148.167.2.224—1
34148.167.2.225/32148.167.2.225 to 148.167.2.225—1
35148.167.2.226/32148.167.2.226 to 148.167.2.226—1
36148.167.2.227/32148.167.2.227 to 148.167.2.227—1
37148.167.2.228/32148.167.2.228 to 148.167.2.228—1
38148.167.2.229/32148.167.2.229 to 148.167.2.229—1
39148.167.2.230/32148.167.2.230 to 148.167.2.230—1
40148.167.2.231/32148.167.2.231 to 148.167.2.231—1
41148.167.2.232/32148.167.2.232 to 148.167.2.232—1
42148.167.2.233/32148.167.2.233 to 148.167.2.233—1
43148.167.2.234/32148.167.2.234 to 148.167.2.234—1
44148.167.2.235/32148.167.2.235 to 148.167.2.235—1
45148.167.2.236/32148.167.2.236 to 148.167.2.236—1
46148.167.2.237/32148.167.2.237 to 148.167.2.237—1
47148.167.2.238/32148.167.2.238 to 148.167.2.238—1
48148.167.2.239/32148.167.2.239 to 148.167.2.239—1
49148.167.2.240/32148.167.2.240 to 148.167.2.240—1
50148.167.2.241/32148.167.2.241 to 148.167.2.241—1
51148.167.2.242/32148.167.2.242 to 148.167.2.242—1
52148.167.2.243/32148.167.2.243 to 148.167.2.243—1
53148.167.2.244/32148.167.2.244 to 148.167.2.244—1
54148.167.2.245/32148.167.2.245 to 148.167.2.245—1
55148.167.2.246/32148.167.2.246 to 148.167.2.246—1
56148.167.2.247/32148.167.2.247 to 148.167.2.247—1
57148.167.2.248/32148.167.2.248 to 148.167.2.248—1
58148.167.2.249/32148.167.2.249 to 148.167.2.249—1
59148.167.2.250/32148.167.2.250 to 148.167.2.250—1
60148.167.2.251/32148.167.2.251 to 148.167.2.251—1
61148.167.2.252/32148.167.2.252 to 148.167.2.252—1
62148.167.2.253/32148.167.2.253 to 148.167.2.253—1
63148.167.2.254/32148.167.2.254 to 148.167.2.254—1
64148.167.2.255/32148.167.2.255 to 148.167.2.255—1

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.