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.

Network229.71.0.0/19
Usable hosts8,190
Subnet mask255.255.224.0
Addresses8,192
Network address
229.71.0.0
Broadcast address
229.71.31.255
First usable
229.71.0.1
Last usable
229.71.31.254
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
Multicast 224.0.0.0/4
One-to-many traffic, such as IPTV and routing protocols
Old class
D (multicast)
As numbers
Hex E5470000 · Integer 3846635520 to 3846643711
Reverse DNS zones
0.71.229.in-addr.arpa
1.71.229.in-addr.arpa
2.71.229.in-addr.arpa
3.71.229.in-addr.arpa
4.71.229.in-addr.arpa
5.71.229.in-addr.arpa
6.71.229.in-addr.arpa
7.71.229.in-addr.arpa
8.71.229.in-addr.arpa
9.71.229.in-addr.arpa
10.71.229.in-addr.arpa
11.71.229.in-addr.arpa
12.71.229.in-addr.arpa
13.71.229.in-addr.arpa
14.71.229.in-addr.arpa
15.71.229.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
Address11100101.01000111.00000000.00000000229.71.0.0
Subnet mask11111111.11111111.11100000.00000000255.255.224.0
Network11100101.01000111.00000000.00000000229.71.0.0
Broadcast11100101.01000111.00011111.11111111229.71.31.255
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)

229.71.0.0/19 makes 128 subnets of /26.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1229.71.0.0/26229.71.0.1 to 229.71.0.62229.71.0.6362
2229.71.0.64/26229.71.0.65 to 229.71.0.126229.71.0.12762
3229.71.0.128/26229.71.0.129 to 229.71.0.190229.71.0.19162
4229.71.0.192/26229.71.0.193 to 229.71.0.254229.71.0.25562
5229.71.1.0/26229.71.1.1 to 229.71.1.62229.71.1.6362
6229.71.1.64/26229.71.1.65 to 229.71.1.126229.71.1.12762
7229.71.1.128/26229.71.1.129 to 229.71.1.190229.71.1.19162
8229.71.1.192/26229.71.1.193 to 229.71.1.254229.71.1.25562
9229.71.2.0/26229.71.2.1 to 229.71.2.62229.71.2.6362
10229.71.2.64/26229.71.2.65 to 229.71.2.126229.71.2.12762
11229.71.2.128/26229.71.2.129 to 229.71.2.190229.71.2.19162
12229.71.2.192/26229.71.2.193 to 229.71.2.254229.71.2.25562
13229.71.3.0/26229.71.3.1 to 229.71.3.62229.71.3.6362
14229.71.3.64/26229.71.3.65 to 229.71.3.126229.71.3.12762
15229.71.3.128/26229.71.3.129 to 229.71.3.190229.71.3.19162
16229.71.3.192/26229.71.3.193 to 229.71.3.254229.71.3.25562
17229.71.4.0/26229.71.4.1 to 229.71.4.62229.71.4.6362
18229.71.4.64/26229.71.4.65 to 229.71.4.126229.71.4.12762
19229.71.4.128/26229.71.4.129 to 229.71.4.190229.71.4.19162
20229.71.4.192/26229.71.4.193 to 229.71.4.254229.71.4.25562
21229.71.5.0/26229.71.5.1 to 229.71.5.62229.71.5.6362
22229.71.5.64/26229.71.5.65 to 229.71.5.126229.71.5.12762
23229.71.5.128/26229.71.5.129 to 229.71.5.190229.71.5.19162
24229.71.5.192/26229.71.5.193 to 229.71.5.254229.71.5.25562
25229.71.6.0/26229.71.6.1 to 229.71.6.62229.71.6.6362
26229.71.6.64/26229.71.6.65 to 229.71.6.126229.71.6.12762
27229.71.6.128/26229.71.6.129 to 229.71.6.190229.71.6.19162
28229.71.6.192/26229.71.6.193 to 229.71.6.254229.71.6.25562
29229.71.7.0/26229.71.7.1 to 229.71.7.62229.71.7.6362
30229.71.7.64/26229.71.7.65 to 229.71.7.126229.71.7.12762
31229.71.7.128/26229.71.7.129 to 229.71.7.190229.71.7.19162
32229.71.7.192/26229.71.7.193 to 229.71.7.254229.71.7.25562
33229.71.8.0/26229.71.8.1 to 229.71.8.62229.71.8.6362
34229.71.8.64/26229.71.8.65 to 229.71.8.126229.71.8.12762
35229.71.8.128/26229.71.8.129 to 229.71.8.190229.71.8.19162
36229.71.8.192/26229.71.8.193 to 229.71.8.254229.71.8.25562
37229.71.9.0/26229.71.9.1 to 229.71.9.62229.71.9.6362
38229.71.9.64/26229.71.9.65 to 229.71.9.126229.71.9.12762
39229.71.9.128/26229.71.9.129 to 229.71.9.190229.71.9.19162
40229.71.9.192/26229.71.9.193 to 229.71.9.254229.71.9.25562
41229.71.10.0/26229.71.10.1 to 229.71.10.62229.71.10.6362
42229.71.10.64/26229.71.10.65 to 229.71.10.126229.71.10.12762
43229.71.10.128/26229.71.10.129 to 229.71.10.190229.71.10.19162
44229.71.10.192/26229.71.10.193 to 229.71.10.254229.71.10.25562
45229.71.11.0/26229.71.11.1 to 229.71.11.62229.71.11.6362
46229.71.11.64/26229.71.11.65 to 229.71.11.126229.71.11.12762
47229.71.11.128/26229.71.11.129 to 229.71.11.190229.71.11.19162
48229.71.11.192/26229.71.11.193 to 229.71.11.254229.71.11.25562
49229.71.12.0/26229.71.12.1 to 229.71.12.62229.71.12.6362
50229.71.12.64/26229.71.12.65 to 229.71.12.126229.71.12.12762
51229.71.12.128/26229.71.12.129 to 229.71.12.190229.71.12.19162
52229.71.12.192/26229.71.12.193 to 229.71.12.254229.71.12.25562
53229.71.13.0/26229.71.13.1 to 229.71.13.62229.71.13.6362
54229.71.13.64/26229.71.13.65 to 229.71.13.126229.71.13.12762
55229.71.13.128/26229.71.13.129 to 229.71.13.190229.71.13.19162
56229.71.13.192/26229.71.13.193 to 229.71.13.254229.71.13.25562
57229.71.14.0/26229.71.14.1 to 229.71.14.62229.71.14.6362
58229.71.14.64/26229.71.14.65 to 229.71.14.126229.71.14.12762
59229.71.14.128/26229.71.14.129 to 229.71.14.190229.71.14.19162
60229.71.14.192/26229.71.14.193 to 229.71.14.254229.71.14.25562
61229.71.15.0/26229.71.15.1 to 229.71.15.62229.71.15.6362
62229.71.15.64/26229.71.15.65 to 229.71.15.126229.71.15.12762
63229.71.15.128/26229.71.15.129 to 229.71.15.190229.71.15.19162
64229.71.15.192/26229.71.15.193 to 229.71.15.254229.71.15.25562
65229.71.16.0/26229.71.16.1 to 229.71.16.62229.71.16.6362
66229.71.16.64/26229.71.16.65 to 229.71.16.126229.71.16.12762
67229.71.16.128/26229.71.16.129 to 229.71.16.190229.71.16.19162
68229.71.16.192/26229.71.16.193 to 229.71.16.254229.71.16.25562
69229.71.17.0/26229.71.17.1 to 229.71.17.62229.71.17.6362
70229.71.17.64/26229.71.17.65 to 229.71.17.126229.71.17.12762
71229.71.17.128/26229.71.17.129 to 229.71.17.190229.71.17.19162
72229.71.17.192/26229.71.17.193 to 229.71.17.254229.71.17.25562
73229.71.18.0/26229.71.18.1 to 229.71.18.62229.71.18.6362
74229.71.18.64/26229.71.18.65 to 229.71.18.126229.71.18.12762
75229.71.18.128/26229.71.18.129 to 229.71.18.190229.71.18.19162
76229.71.18.192/26229.71.18.193 to 229.71.18.254229.71.18.25562
77229.71.19.0/26229.71.19.1 to 229.71.19.62229.71.19.6362
78229.71.19.64/26229.71.19.65 to 229.71.19.126229.71.19.12762
79229.71.19.128/26229.71.19.129 to 229.71.19.190229.71.19.19162
80229.71.19.192/26229.71.19.193 to 229.71.19.254229.71.19.25562
81229.71.20.0/26229.71.20.1 to 229.71.20.62229.71.20.6362
82229.71.20.64/26229.71.20.65 to 229.71.20.126229.71.20.12762
83229.71.20.128/26229.71.20.129 to 229.71.20.190229.71.20.19162
84229.71.20.192/26229.71.20.193 to 229.71.20.254229.71.20.25562
85229.71.21.0/26229.71.21.1 to 229.71.21.62229.71.21.6362
86229.71.21.64/26229.71.21.65 to 229.71.21.126229.71.21.12762
87229.71.21.128/26229.71.21.129 to 229.71.21.190229.71.21.19162
88229.71.21.192/26229.71.21.193 to 229.71.21.254229.71.21.25562
89229.71.22.0/26229.71.22.1 to 229.71.22.62229.71.22.6362
90229.71.22.64/26229.71.22.65 to 229.71.22.126229.71.22.12762
91229.71.22.128/26229.71.22.129 to 229.71.22.190229.71.22.19162
92229.71.22.192/26229.71.22.193 to 229.71.22.254229.71.22.25562
93229.71.23.0/26229.71.23.1 to 229.71.23.62229.71.23.6362
94229.71.23.64/26229.71.23.65 to 229.71.23.126229.71.23.12762
95229.71.23.128/26229.71.23.129 to 229.71.23.190229.71.23.19162
96229.71.23.192/26229.71.23.193 to 229.71.23.254229.71.23.25562
97229.71.24.0/26229.71.24.1 to 229.71.24.62229.71.24.6362
98229.71.24.64/26229.71.24.65 to 229.71.24.126229.71.24.12762
99229.71.24.128/26229.71.24.129 to 229.71.24.190229.71.24.19162
100229.71.24.192/26229.71.24.193 to 229.71.24.254229.71.24.25562
101229.71.25.0/26229.71.25.1 to 229.71.25.62229.71.25.6362
102229.71.25.64/26229.71.25.65 to 229.71.25.126229.71.25.12762
103229.71.25.128/26229.71.25.129 to 229.71.25.190229.71.25.19162
104229.71.25.192/26229.71.25.193 to 229.71.25.254229.71.25.25562
105229.71.26.0/26229.71.26.1 to 229.71.26.62229.71.26.6362
106229.71.26.64/26229.71.26.65 to 229.71.26.126229.71.26.12762
107229.71.26.128/26229.71.26.129 to 229.71.26.190229.71.26.19162
108229.71.26.192/26229.71.26.193 to 229.71.26.254229.71.26.25562
109229.71.27.0/26229.71.27.1 to 229.71.27.62229.71.27.6362
110229.71.27.64/26229.71.27.65 to 229.71.27.126229.71.27.12762
111229.71.27.128/26229.71.27.129 to 229.71.27.190229.71.27.19162
112229.71.27.192/26229.71.27.193 to 229.71.27.254229.71.27.25562
113229.71.28.0/26229.71.28.1 to 229.71.28.62229.71.28.6362
114229.71.28.64/26229.71.28.65 to 229.71.28.126229.71.28.12762
115229.71.28.128/26229.71.28.129 to 229.71.28.190229.71.28.19162
116229.71.28.192/26229.71.28.193 to 229.71.28.254229.71.28.25562
117229.71.29.0/26229.71.29.1 to 229.71.29.62229.71.29.6362
118229.71.29.64/26229.71.29.65 to 229.71.29.126229.71.29.12762
119229.71.29.128/26229.71.29.129 to 229.71.29.190229.71.29.19162
120229.71.29.192/26229.71.29.193 to 229.71.29.254229.71.29.25562
121229.71.30.0/26229.71.30.1 to 229.71.30.62229.71.30.6362
122229.71.30.64/26229.71.30.65 to 229.71.30.126229.71.30.12762
123229.71.30.128/26229.71.30.129 to 229.71.30.190229.71.30.19162
124229.71.30.192/26229.71.30.193 to 229.71.30.254229.71.30.25562
125229.71.31.0/26229.71.31.1 to 229.71.31.62229.71.31.6362
126229.71.31.64/26229.71.31.65 to 229.71.31.126229.71.31.12762
127229.71.31.128/26229.71.31.129 to 229.71.31.190229.71.31.19162
128229.71.31.192/26229.71.31.193 to 229.71.31.254229.71.31.25562

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.