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.

Network37.192.0.0/13
Usable hosts524,286
Subnet mask255.248.0.0
Addresses524,288
Network address
37.192.0.0
Broadcast address
37.199.255.255
First usable
37.192.0.1
Last usable
37.199.255.254
Usable hosts
524,286 (524,288 less the network and broadcast addresses)
Subnet mask
255.248.0.0
Wildcard mask
0.7.255.255 (Cisco ACLs, OSPF)
Prefix length
/13
Type
Public public
Old class
A (default /8)
As numbers
Hex 25C00000 · Integer 633339904 to 633864191
Reverse DNS zones
192.37.in-addr.arpa
193.37.in-addr.arpa
194.37.in-addr.arpa
195.37.in-addr.arpa
196.37.in-addr.arpa
197.37.in-addr.arpa
198.37.in-addr.arpa
199.37.in-addr.arpa
/13 is not on a 8-bit boundary, so it takes 8 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00100101.11000000.00000000.0000000037.192.0.0
Subnet mask11111111.11111000.00000000.00000000255.248.0.0
Network00100101.11000000.00000000.0000000037.192.0.0
Broadcast00100101.11000111.11111111.1111111137.199.255.255
Split into smaller subnets/20

37.192.0.0/13 makes 128 subnets of /20.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
137.192.0.0/2037.192.0.1 to 37.192.15.25437.192.15.2554,094
237.192.16.0/2037.192.16.1 to 37.192.31.25437.192.31.2554,094
337.192.32.0/2037.192.32.1 to 37.192.47.25437.192.47.2554,094
437.192.48.0/2037.192.48.1 to 37.192.63.25437.192.63.2554,094
537.192.64.0/2037.192.64.1 to 37.192.79.25437.192.79.2554,094
637.192.80.0/2037.192.80.1 to 37.192.95.25437.192.95.2554,094
737.192.96.0/2037.192.96.1 to 37.192.111.25437.192.111.2554,094
837.192.112.0/2037.192.112.1 to 37.192.127.25437.192.127.2554,094
937.192.128.0/2037.192.128.1 to 37.192.143.25437.192.143.2554,094
1037.192.144.0/2037.192.144.1 to 37.192.159.25437.192.159.2554,094
1137.192.160.0/2037.192.160.1 to 37.192.175.25437.192.175.2554,094
1237.192.176.0/2037.192.176.1 to 37.192.191.25437.192.191.2554,094
1337.192.192.0/2037.192.192.1 to 37.192.207.25437.192.207.2554,094
1437.192.208.0/2037.192.208.1 to 37.192.223.25437.192.223.2554,094
1537.192.224.0/2037.192.224.1 to 37.192.239.25437.192.239.2554,094
1637.192.240.0/2037.192.240.1 to 37.192.255.25437.192.255.2554,094
1737.193.0.0/2037.193.0.1 to 37.193.15.25437.193.15.2554,094
1837.193.16.0/2037.193.16.1 to 37.193.31.25437.193.31.2554,094
1937.193.32.0/2037.193.32.1 to 37.193.47.25437.193.47.2554,094
2037.193.48.0/2037.193.48.1 to 37.193.63.25437.193.63.2554,094
2137.193.64.0/2037.193.64.1 to 37.193.79.25437.193.79.2554,094
2237.193.80.0/2037.193.80.1 to 37.193.95.25437.193.95.2554,094
2337.193.96.0/2037.193.96.1 to 37.193.111.25437.193.111.2554,094
2437.193.112.0/2037.193.112.1 to 37.193.127.25437.193.127.2554,094
2537.193.128.0/2037.193.128.1 to 37.193.143.25437.193.143.2554,094
2637.193.144.0/2037.193.144.1 to 37.193.159.25437.193.159.2554,094
2737.193.160.0/2037.193.160.1 to 37.193.175.25437.193.175.2554,094
2837.193.176.0/2037.193.176.1 to 37.193.191.25437.193.191.2554,094
2937.193.192.0/2037.193.192.1 to 37.193.207.25437.193.207.2554,094
3037.193.208.0/2037.193.208.1 to 37.193.223.25437.193.223.2554,094
3137.193.224.0/2037.193.224.1 to 37.193.239.25437.193.239.2554,094
3237.193.240.0/2037.193.240.1 to 37.193.255.25437.193.255.2554,094
3337.194.0.0/2037.194.0.1 to 37.194.15.25437.194.15.2554,094
3437.194.16.0/2037.194.16.1 to 37.194.31.25437.194.31.2554,094
3537.194.32.0/2037.194.32.1 to 37.194.47.25437.194.47.2554,094
3637.194.48.0/2037.194.48.1 to 37.194.63.25437.194.63.2554,094
3737.194.64.0/2037.194.64.1 to 37.194.79.25437.194.79.2554,094
3837.194.80.0/2037.194.80.1 to 37.194.95.25437.194.95.2554,094
3937.194.96.0/2037.194.96.1 to 37.194.111.25437.194.111.2554,094
4037.194.112.0/2037.194.112.1 to 37.194.127.25437.194.127.2554,094
4137.194.128.0/2037.194.128.1 to 37.194.143.25437.194.143.2554,094
4237.194.144.0/2037.194.144.1 to 37.194.159.25437.194.159.2554,094
4337.194.160.0/2037.194.160.1 to 37.194.175.25437.194.175.2554,094
4437.194.176.0/2037.194.176.1 to 37.194.191.25437.194.191.2554,094
4537.194.192.0/2037.194.192.1 to 37.194.207.25437.194.207.2554,094
4637.194.208.0/2037.194.208.1 to 37.194.223.25437.194.223.2554,094
4737.194.224.0/2037.194.224.1 to 37.194.239.25437.194.239.2554,094
4837.194.240.0/2037.194.240.1 to 37.194.255.25437.194.255.2554,094
4937.195.0.0/2037.195.0.1 to 37.195.15.25437.195.15.2554,094
5037.195.16.0/2037.195.16.1 to 37.195.31.25437.195.31.2554,094
5137.195.32.0/2037.195.32.1 to 37.195.47.25437.195.47.2554,094
5237.195.48.0/2037.195.48.1 to 37.195.63.25437.195.63.2554,094
5337.195.64.0/2037.195.64.1 to 37.195.79.25437.195.79.2554,094
5437.195.80.0/2037.195.80.1 to 37.195.95.25437.195.95.2554,094
5537.195.96.0/2037.195.96.1 to 37.195.111.25437.195.111.2554,094
5637.195.112.0/2037.195.112.1 to 37.195.127.25437.195.127.2554,094
5737.195.128.0/2037.195.128.1 to 37.195.143.25437.195.143.2554,094
5837.195.144.0/2037.195.144.1 to 37.195.159.25437.195.159.2554,094
5937.195.160.0/2037.195.160.1 to 37.195.175.25437.195.175.2554,094
6037.195.176.0/2037.195.176.1 to 37.195.191.25437.195.191.2554,094
6137.195.192.0/2037.195.192.1 to 37.195.207.25437.195.207.2554,094
6237.195.208.0/2037.195.208.1 to 37.195.223.25437.195.223.2554,094
6337.195.224.0/2037.195.224.1 to 37.195.239.25437.195.239.2554,094
6437.195.240.0/2037.195.240.1 to 37.195.255.25437.195.255.2554,094
6537.196.0.0/2037.196.0.1 to 37.196.15.25437.196.15.2554,094
6637.196.16.0/2037.196.16.1 to 37.196.31.25437.196.31.2554,094
6737.196.32.0/2037.196.32.1 to 37.196.47.25437.196.47.2554,094
6837.196.48.0/2037.196.48.1 to 37.196.63.25437.196.63.2554,094
6937.196.64.0/2037.196.64.1 to 37.196.79.25437.196.79.2554,094
7037.196.80.0/2037.196.80.1 to 37.196.95.25437.196.95.2554,094
7137.196.96.0/2037.196.96.1 to 37.196.111.25437.196.111.2554,094
7237.196.112.0/2037.196.112.1 to 37.196.127.25437.196.127.2554,094
7337.196.128.0/2037.196.128.1 to 37.196.143.25437.196.143.2554,094
7437.196.144.0/2037.196.144.1 to 37.196.159.25437.196.159.2554,094
7537.196.160.0/2037.196.160.1 to 37.196.175.25437.196.175.2554,094
7637.196.176.0/2037.196.176.1 to 37.196.191.25437.196.191.2554,094
7737.196.192.0/2037.196.192.1 to 37.196.207.25437.196.207.2554,094
7837.196.208.0/2037.196.208.1 to 37.196.223.25437.196.223.2554,094
7937.196.224.0/2037.196.224.1 to 37.196.239.25437.196.239.2554,094
8037.196.240.0/2037.196.240.1 to 37.196.255.25437.196.255.2554,094
8137.197.0.0/2037.197.0.1 to 37.197.15.25437.197.15.2554,094
8237.197.16.0/2037.197.16.1 to 37.197.31.25437.197.31.2554,094
8337.197.32.0/2037.197.32.1 to 37.197.47.25437.197.47.2554,094
8437.197.48.0/2037.197.48.1 to 37.197.63.25437.197.63.2554,094
8537.197.64.0/2037.197.64.1 to 37.197.79.25437.197.79.2554,094
8637.197.80.0/2037.197.80.1 to 37.197.95.25437.197.95.2554,094
8737.197.96.0/2037.197.96.1 to 37.197.111.25437.197.111.2554,094
8837.197.112.0/2037.197.112.1 to 37.197.127.25437.197.127.2554,094
8937.197.128.0/2037.197.128.1 to 37.197.143.25437.197.143.2554,094
9037.197.144.0/2037.197.144.1 to 37.197.159.25437.197.159.2554,094
9137.197.160.0/2037.197.160.1 to 37.197.175.25437.197.175.2554,094
9237.197.176.0/2037.197.176.1 to 37.197.191.25437.197.191.2554,094
9337.197.192.0/2037.197.192.1 to 37.197.207.25437.197.207.2554,094
9437.197.208.0/2037.197.208.1 to 37.197.223.25437.197.223.2554,094
9537.197.224.0/2037.197.224.1 to 37.197.239.25437.197.239.2554,094
9637.197.240.0/2037.197.240.1 to 37.197.255.25437.197.255.2554,094
9737.198.0.0/2037.198.0.1 to 37.198.15.25437.198.15.2554,094
9837.198.16.0/2037.198.16.1 to 37.198.31.25437.198.31.2554,094
9937.198.32.0/2037.198.32.1 to 37.198.47.25437.198.47.2554,094
10037.198.48.0/2037.198.48.1 to 37.198.63.25437.198.63.2554,094
10137.198.64.0/2037.198.64.1 to 37.198.79.25437.198.79.2554,094
10237.198.80.0/2037.198.80.1 to 37.198.95.25437.198.95.2554,094
10337.198.96.0/2037.198.96.1 to 37.198.111.25437.198.111.2554,094
10437.198.112.0/2037.198.112.1 to 37.198.127.25437.198.127.2554,094
10537.198.128.0/2037.198.128.1 to 37.198.143.25437.198.143.2554,094
10637.198.144.0/2037.198.144.1 to 37.198.159.25437.198.159.2554,094
10737.198.160.0/2037.198.160.1 to 37.198.175.25437.198.175.2554,094
10837.198.176.0/2037.198.176.1 to 37.198.191.25437.198.191.2554,094
10937.198.192.0/2037.198.192.1 to 37.198.207.25437.198.207.2554,094
11037.198.208.0/2037.198.208.1 to 37.198.223.25437.198.223.2554,094
11137.198.224.0/2037.198.224.1 to 37.198.239.25437.198.239.2554,094
11237.198.240.0/2037.198.240.1 to 37.198.255.25437.198.255.2554,094
11337.199.0.0/2037.199.0.1 to 37.199.15.25437.199.15.2554,094
11437.199.16.0/2037.199.16.1 to 37.199.31.25437.199.31.2554,094
11537.199.32.0/2037.199.32.1 to 37.199.47.25437.199.47.2554,094
11637.199.48.0/2037.199.48.1 to 37.199.63.25437.199.63.2554,094
11737.199.64.0/2037.199.64.1 to 37.199.79.25437.199.79.2554,094
11837.199.80.0/2037.199.80.1 to 37.199.95.25437.199.95.2554,094
11937.199.96.0/2037.199.96.1 to 37.199.111.25437.199.111.2554,094
12037.199.112.0/2037.199.112.1 to 37.199.127.25437.199.127.2554,094
12137.199.128.0/2037.199.128.1 to 37.199.143.25437.199.143.2554,094
12237.199.144.0/2037.199.144.1 to 37.199.159.25437.199.159.2554,094
12337.199.160.0/2037.199.160.1 to 37.199.175.25437.199.175.2554,094
12437.199.176.0/2037.199.176.1 to 37.199.191.25437.199.191.2554,094
12537.199.192.0/2037.199.192.1 to 37.199.207.25437.199.207.2554,094
12637.199.208.0/2037.199.208.1 to 37.199.223.25437.199.223.2554,094
12737.199.224.0/2037.199.224.1 to 37.199.239.25437.199.239.2554,094
12837.199.240.0/2037.199.240.1 to 37.199.255.25437.199.255.2554,094

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