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.

Network205.0.0.0/13
Usable hosts524,286
Subnet mask255.248.0.0
Addresses524,288
Network address
205.0.0.0
Broadcast address
205.7.255.255
First usable
205.0.0.1
Last usable
205.7.255.254
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
C (default /24)
As numbers
Hex CD000000 · Integer 3439329280 to 3439853567
Reverse DNS zones
0.205.in-addr.arpa
1.205.in-addr.arpa
2.205.in-addr.arpa
3.205.in-addr.arpa
4.205.in-addr.arpa
5.205.in-addr.arpa
6.205.in-addr.arpa
7.205.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
Address11001101.00000000.00000000.00000000205.0.0.0
Subnet mask11111111.11111000.00000000.00000000255.248.0.0
Network11001101.00000000.00000000.00000000205.0.0.0
Broadcast11001101.00000111.11111111.11111111205.7.255.255
Split into smaller subnets/22
/14 (2)/15 (4)/16 (8)/17 (16)/18 (32)/19 (64)/20 (128)/21 (256)/22 (512)/23 (1,024)/24 (2,048)/25 (4,096)

205.0.0.0/13 makes 512 subnets of /22; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1205.0.0.0/22205.0.0.1 to 205.0.3.254205.0.3.2551,022
2205.0.4.0/22205.0.4.1 to 205.0.7.254205.0.7.2551,022
3205.0.8.0/22205.0.8.1 to 205.0.11.254205.0.11.2551,022
4205.0.12.0/22205.0.12.1 to 205.0.15.254205.0.15.2551,022
5205.0.16.0/22205.0.16.1 to 205.0.19.254205.0.19.2551,022
6205.0.20.0/22205.0.20.1 to 205.0.23.254205.0.23.2551,022
7205.0.24.0/22205.0.24.1 to 205.0.27.254205.0.27.2551,022
8205.0.28.0/22205.0.28.1 to 205.0.31.254205.0.31.2551,022
9205.0.32.0/22205.0.32.1 to 205.0.35.254205.0.35.2551,022
10205.0.36.0/22205.0.36.1 to 205.0.39.254205.0.39.2551,022
11205.0.40.0/22205.0.40.1 to 205.0.43.254205.0.43.2551,022
12205.0.44.0/22205.0.44.1 to 205.0.47.254205.0.47.2551,022
13205.0.48.0/22205.0.48.1 to 205.0.51.254205.0.51.2551,022
14205.0.52.0/22205.0.52.1 to 205.0.55.254205.0.55.2551,022
15205.0.56.0/22205.0.56.1 to 205.0.59.254205.0.59.2551,022
16205.0.60.0/22205.0.60.1 to 205.0.63.254205.0.63.2551,022
17205.0.64.0/22205.0.64.1 to 205.0.67.254205.0.67.2551,022
18205.0.68.0/22205.0.68.1 to 205.0.71.254205.0.71.2551,022
19205.0.72.0/22205.0.72.1 to 205.0.75.254205.0.75.2551,022
20205.0.76.0/22205.0.76.1 to 205.0.79.254205.0.79.2551,022
21205.0.80.0/22205.0.80.1 to 205.0.83.254205.0.83.2551,022
22205.0.84.0/22205.0.84.1 to 205.0.87.254205.0.87.2551,022
23205.0.88.0/22205.0.88.1 to 205.0.91.254205.0.91.2551,022
24205.0.92.0/22205.0.92.1 to 205.0.95.254205.0.95.2551,022
25205.0.96.0/22205.0.96.1 to 205.0.99.254205.0.99.2551,022
26205.0.100.0/22205.0.100.1 to 205.0.103.254205.0.103.2551,022
27205.0.104.0/22205.0.104.1 to 205.0.107.254205.0.107.2551,022
28205.0.108.0/22205.0.108.1 to 205.0.111.254205.0.111.2551,022
29205.0.112.0/22205.0.112.1 to 205.0.115.254205.0.115.2551,022
30205.0.116.0/22205.0.116.1 to 205.0.119.254205.0.119.2551,022
31205.0.120.0/22205.0.120.1 to 205.0.123.254205.0.123.2551,022
32205.0.124.0/22205.0.124.1 to 205.0.127.254205.0.127.2551,022
33205.0.128.0/22205.0.128.1 to 205.0.131.254205.0.131.2551,022
34205.0.132.0/22205.0.132.1 to 205.0.135.254205.0.135.2551,022
35205.0.136.0/22205.0.136.1 to 205.0.139.254205.0.139.2551,022
36205.0.140.0/22205.0.140.1 to 205.0.143.254205.0.143.2551,022
37205.0.144.0/22205.0.144.1 to 205.0.147.254205.0.147.2551,022
38205.0.148.0/22205.0.148.1 to 205.0.151.254205.0.151.2551,022
39205.0.152.0/22205.0.152.1 to 205.0.155.254205.0.155.2551,022
40205.0.156.0/22205.0.156.1 to 205.0.159.254205.0.159.2551,022
41205.0.160.0/22205.0.160.1 to 205.0.163.254205.0.163.2551,022
42205.0.164.0/22205.0.164.1 to 205.0.167.254205.0.167.2551,022
43205.0.168.0/22205.0.168.1 to 205.0.171.254205.0.171.2551,022
44205.0.172.0/22205.0.172.1 to 205.0.175.254205.0.175.2551,022
45205.0.176.0/22205.0.176.1 to 205.0.179.254205.0.179.2551,022
46205.0.180.0/22205.0.180.1 to 205.0.183.254205.0.183.2551,022
47205.0.184.0/22205.0.184.1 to 205.0.187.254205.0.187.2551,022
48205.0.188.0/22205.0.188.1 to 205.0.191.254205.0.191.2551,022
49205.0.192.0/22205.0.192.1 to 205.0.195.254205.0.195.2551,022
50205.0.196.0/22205.0.196.1 to 205.0.199.254205.0.199.2551,022
51205.0.200.0/22205.0.200.1 to 205.0.203.254205.0.203.2551,022
52205.0.204.0/22205.0.204.1 to 205.0.207.254205.0.207.2551,022
53205.0.208.0/22205.0.208.1 to 205.0.211.254205.0.211.2551,022
54205.0.212.0/22205.0.212.1 to 205.0.215.254205.0.215.2551,022
55205.0.216.0/22205.0.216.1 to 205.0.219.254205.0.219.2551,022
56205.0.220.0/22205.0.220.1 to 205.0.223.254205.0.223.2551,022
57205.0.224.0/22205.0.224.1 to 205.0.227.254205.0.227.2551,022
58205.0.228.0/22205.0.228.1 to 205.0.231.254205.0.231.2551,022
59205.0.232.0/22205.0.232.1 to 205.0.235.254205.0.235.2551,022
60205.0.236.0/22205.0.236.1 to 205.0.239.254205.0.239.2551,022
61205.0.240.0/22205.0.240.1 to 205.0.243.254205.0.243.2551,022
62205.0.244.0/22205.0.244.1 to 205.0.247.254205.0.247.2551,022
63205.0.248.0/22205.0.248.1 to 205.0.251.254205.0.251.2551,022
64205.0.252.0/22205.0.252.1 to 205.0.255.254205.0.255.2551,022
65205.1.0.0/22205.1.0.1 to 205.1.3.254205.1.3.2551,022
66205.1.4.0/22205.1.4.1 to 205.1.7.254205.1.7.2551,022
67205.1.8.0/22205.1.8.1 to 205.1.11.254205.1.11.2551,022
68205.1.12.0/22205.1.12.1 to 205.1.15.254205.1.15.2551,022
69205.1.16.0/22205.1.16.1 to 205.1.19.254205.1.19.2551,022
70205.1.20.0/22205.1.20.1 to 205.1.23.254205.1.23.2551,022
71205.1.24.0/22205.1.24.1 to 205.1.27.254205.1.27.2551,022
72205.1.28.0/22205.1.28.1 to 205.1.31.254205.1.31.2551,022
73205.1.32.0/22205.1.32.1 to 205.1.35.254205.1.35.2551,022
74205.1.36.0/22205.1.36.1 to 205.1.39.254205.1.39.2551,022
75205.1.40.0/22205.1.40.1 to 205.1.43.254205.1.43.2551,022
76205.1.44.0/22205.1.44.1 to 205.1.47.254205.1.47.2551,022
77205.1.48.0/22205.1.48.1 to 205.1.51.254205.1.51.2551,022
78205.1.52.0/22205.1.52.1 to 205.1.55.254205.1.55.2551,022
79205.1.56.0/22205.1.56.1 to 205.1.59.254205.1.59.2551,022
80205.1.60.0/22205.1.60.1 to 205.1.63.254205.1.63.2551,022
81205.1.64.0/22205.1.64.1 to 205.1.67.254205.1.67.2551,022
82205.1.68.0/22205.1.68.1 to 205.1.71.254205.1.71.2551,022
83205.1.72.0/22205.1.72.1 to 205.1.75.254205.1.75.2551,022
84205.1.76.0/22205.1.76.1 to 205.1.79.254205.1.79.2551,022
85205.1.80.0/22205.1.80.1 to 205.1.83.254205.1.83.2551,022
86205.1.84.0/22205.1.84.1 to 205.1.87.254205.1.87.2551,022
87205.1.88.0/22205.1.88.1 to 205.1.91.254205.1.91.2551,022
88205.1.92.0/22205.1.92.1 to 205.1.95.254205.1.95.2551,022
89205.1.96.0/22205.1.96.1 to 205.1.99.254205.1.99.2551,022
90205.1.100.0/22205.1.100.1 to 205.1.103.254205.1.103.2551,022
91205.1.104.0/22205.1.104.1 to 205.1.107.254205.1.107.2551,022
92205.1.108.0/22205.1.108.1 to 205.1.111.254205.1.111.2551,022
93205.1.112.0/22205.1.112.1 to 205.1.115.254205.1.115.2551,022
94205.1.116.0/22205.1.116.1 to 205.1.119.254205.1.119.2551,022
95205.1.120.0/22205.1.120.1 to 205.1.123.254205.1.123.2551,022
96205.1.124.0/22205.1.124.1 to 205.1.127.254205.1.127.2551,022
97205.1.128.0/22205.1.128.1 to 205.1.131.254205.1.131.2551,022
98205.1.132.0/22205.1.132.1 to 205.1.135.254205.1.135.2551,022
99205.1.136.0/22205.1.136.1 to 205.1.139.254205.1.139.2551,022
100205.1.140.0/22205.1.140.1 to 205.1.143.254205.1.143.2551,022
101205.1.144.0/22205.1.144.1 to 205.1.147.254205.1.147.2551,022
102205.1.148.0/22205.1.148.1 to 205.1.151.254205.1.151.2551,022
103205.1.152.0/22205.1.152.1 to 205.1.155.254205.1.155.2551,022
104205.1.156.0/22205.1.156.1 to 205.1.159.254205.1.159.2551,022
105205.1.160.0/22205.1.160.1 to 205.1.163.254205.1.163.2551,022
106205.1.164.0/22205.1.164.1 to 205.1.167.254205.1.167.2551,022
107205.1.168.0/22205.1.168.1 to 205.1.171.254205.1.171.2551,022
108205.1.172.0/22205.1.172.1 to 205.1.175.254205.1.175.2551,022
109205.1.176.0/22205.1.176.1 to 205.1.179.254205.1.179.2551,022
110205.1.180.0/22205.1.180.1 to 205.1.183.254205.1.183.2551,022
111205.1.184.0/22205.1.184.1 to 205.1.187.254205.1.187.2551,022
112205.1.188.0/22205.1.188.1 to 205.1.191.254205.1.191.2551,022
113205.1.192.0/22205.1.192.1 to 205.1.195.254205.1.195.2551,022
114205.1.196.0/22205.1.196.1 to 205.1.199.254205.1.199.2551,022
115205.1.200.0/22205.1.200.1 to 205.1.203.254205.1.203.2551,022
116205.1.204.0/22205.1.204.1 to 205.1.207.254205.1.207.2551,022
117205.1.208.0/22205.1.208.1 to 205.1.211.254205.1.211.2551,022
118205.1.212.0/22205.1.212.1 to 205.1.215.254205.1.215.2551,022
119205.1.216.0/22205.1.216.1 to 205.1.219.254205.1.219.2551,022
120205.1.220.0/22205.1.220.1 to 205.1.223.254205.1.223.2551,022
121205.1.224.0/22205.1.224.1 to 205.1.227.254205.1.227.2551,022
122205.1.228.0/22205.1.228.1 to 205.1.231.254205.1.231.2551,022
123205.1.232.0/22205.1.232.1 to 205.1.235.254205.1.235.2551,022
124205.1.236.0/22205.1.236.1 to 205.1.239.254205.1.239.2551,022
125205.1.240.0/22205.1.240.1 to 205.1.243.254205.1.243.2551,022
126205.1.244.0/22205.1.244.1 to 205.1.247.254205.1.247.2551,022
127205.1.248.0/22205.1.248.1 to 205.1.251.254205.1.251.2551,022
128205.1.252.0/22205.1.252.1 to 205.1.255.254205.1.255.2551,022
129205.2.0.0/22205.2.0.1 to 205.2.3.254205.2.3.2551,022
130205.2.4.0/22205.2.4.1 to 205.2.7.254205.2.7.2551,022
131205.2.8.0/22205.2.8.1 to 205.2.11.254205.2.11.2551,022
132205.2.12.0/22205.2.12.1 to 205.2.15.254205.2.15.2551,022
133205.2.16.0/22205.2.16.1 to 205.2.19.254205.2.19.2551,022
134205.2.20.0/22205.2.20.1 to 205.2.23.254205.2.23.2551,022
135205.2.24.0/22205.2.24.1 to 205.2.27.254205.2.27.2551,022
136205.2.28.0/22205.2.28.1 to 205.2.31.254205.2.31.2551,022
137205.2.32.0/22205.2.32.1 to 205.2.35.254205.2.35.2551,022
138205.2.36.0/22205.2.36.1 to 205.2.39.254205.2.39.2551,022
139205.2.40.0/22205.2.40.1 to 205.2.43.254205.2.43.2551,022
140205.2.44.0/22205.2.44.1 to 205.2.47.254205.2.47.2551,022
141205.2.48.0/22205.2.48.1 to 205.2.51.254205.2.51.2551,022
142205.2.52.0/22205.2.52.1 to 205.2.55.254205.2.55.2551,022
143205.2.56.0/22205.2.56.1 to 205.2.59.254205.2.59.2551,022
144205.2.60.0/22205.2.60.1 to 205.2.63.254205.2.63.2551,022
145205.2.64.0/22205.2.64.1 to 205.2.67.254205.2.67.2551,022
146205.2.68.0/22205.2.68.1 to 205.2.71.254205.2.71.2551,022
147205.2.72.0/22205.2.72.1 to 205.2.75.254205.2.75.2551,022
148205.2.76.0/22205.2.76.1 to 205.2.79.254205.2.79.2551,022
149205.2.80.0/22205.2.80.1 to 205.2.83.254205.2.83.2551,022
150205.2.84.0/22205.2.84.1 to 205.2.87.254205.2.87.2551,022
151205.2.88.0/22205.2.88.1 to 205.2.91.254205.2.91.2551,022
152205.2.92.0/22205.2.92.1 to 205.2.95.254205.2.95.2551,022
153205.2.96.0/22205.2.96.1 to 205.2.99.254205.2.99.2551,022
154205.2.100.0/22205.2.100.1 to 205.2.103.254205.2.103.2551,022
155205.2.104.0/22205.2.104.1 to 205.2.107.254205.2.107.2551,022
156205.2.108.0/22205.2.108.1 to 205.2.111.254205.2.111.2551,022
157205.2.112.0/22205.2.112.1 to 205.2.115.254205.2.115.2551,022
158205.2.116.0/22205.2.116.1 to 205.2.119.254205.2.119.2551,022
159205.2.120.0/22205.2.120.1 to 205.2.123.254205.2.123.2551,022
160205.2.124.0/22205.2.124.1 to 205.2.127.254205.2.127.2551,022
161205.2.128.0/22205.2.128.1 to 205.2.131.254205.2.131.2551,022
162205.2.132.0/22205.2.132.1 to 205.2.135.254205.2.135.2551,022
163205.2.136.0/22205.2.136.1 to 205.2.139.254205.2.139.2551,022
164205.2.140.0/22205.2.140.1 to 205.2.143.254205.2.143.2551,022
165205.2.144.0/22205.2.144.1 to 205.2.147.254205.2.147.2551,022
166205.2.148.0/22205.2.148.1 to 205.2.151.254205.2.151.2551,022
167205.2.152.0/22205.2.152.1 to 205.2.155.254205.2.155.2551,022
168205.2.156.0/22205.2.156.1 to 205.2.159.254205.2.159.2551,022
169205.2.160.0/22205.2.160.1 to 205.2.163.254205.2.163.2551,022
170205.2.164.0/22205.2.164.1 to 205.2.167.254205.2.167.2551,022
171205.2.168.0/22205.2.168.1 to 205.2.171.254205.2.171.2551,022
172205.2.172.0/22205.2.172.1 to 205.2.175.254205.2.175.2551,022
173205.2.176.0/22205.2.176.1 to 205.2.179.254205.2.179.2551,022
174205.2.180.0/22205.2.180.1 to 205.2.183.254205.2.183.2551,022
175205.2.184.0/22205.2.184.1 to 205.2.187.254205.2.187.2551,022
176205.2.188.0/22205.2.188.1 to 205.2.191.254205.2.191.2551,022
177205.2.192.0/22205.2.192.1 to 205.2.195.254205.2.195.2551,022
178205.2.196.0/22205.2.196.1 to 205.2.199.254205.2.199.2551,022
179205.2.200.0/22205.2.200.1 to 205.2.203.254205.2.203.2551,022
180205.2.204.0/22205.2.204.1 to 205.2.207.254205.2.207.2551,022
181205.2.208.0/22205.2.208.1 to 205.2.211.254205.2.211.2551,022
182205.2.212.0/22205.2.212.1 to 205.2.215.254205.2.215.2551,022
183205.2.216.0/22205.2.216.1 to 205.2.219.254205.2.219.2551,022
184205.2.220.0/22205.2.220.1 to 205.2.223.254205.2.223.2551,022
185205.2.224.0/22205.2.224.1 to 205.2.227.254205.2.227.2551,022
186205.2.228.0/22205.2.228.1 to 205.2.231.254205.2.231.2551,022
187205.2.232.0/22205.2.232.1 to 205.2.235.254205.2.235.2551,022
188205.2.236.0/22205.2.236.1 to 205.2.239.254205.2.239.2551,022
189205.2.240.0/22205.2.240.1 to 205.2.243.254205.2.243.2551,022
190205.2.244.0/22205.2.244.1 to 205.2.247.254205.2.247.2551,022
191205.2.248.0/22205.2.248.1 to 205.2.251.254205.2.251.2551,022
192205.2.252.0/22205.2.252.1 to 205.2.255.254205.2.255.2551,022
193205.3.0.0/22205.3.0.1 to 205.3.3.254205.3.3.2551,022
194205.3.4.0/22205.3.4.1 to 205.3.7.254205.3.7.2551,022
195205.3.8.0/22205.3.8.1 to 205.3.11.254205.3.11.2551,022
196205.3.12.0/22205.3.12.1 to 205.3.15.254205.3.15.2551,022
197205.3.16.0/22205.3.16.1 to 205.3.19.254205.3.19.2551,022
198205.3.20.0/22205.3.20.1 to 205.3.23.254205.3.23.2551,022
199205.3.24.0/22205.3.24.1 to 205.3.27.254205.3.27.2551,022
200205.3.28.0/22205.3.28.1 to 205.3.31.254205.3.31.2551,022
201205.3.32.0/22205.3.32.1 to 205.3.35.254205.3.35.2551,022
202205.3.36.0/22205.3.36.1 to 205.3.39.254205.3.39.2551,022
203205.3.40.0/22205.3.40.1 to 205.3.43.254205.3.43.2551,022
204205.3.44.0/22205.3.44.1 to 205.3.47.254205.3.47.2551,022
205205.3.48.0/22205.3.48.1 to 205.3.51.254205.3.51.2551,022
206205.3.52.0/22205.3.52.1 to 205.3.55.254205.3.55.2551,022
207205.3.56.0/22205.3.56.1 to 205.3.59.254205.3.59.2551,022
208205.3.60.0/22205.3.60.1 to 205.3.63.254205.3.63.2551,022
209205.3.64.0/22205.3.64.1 to 205.3.67.254205.3.67.2551,022
210205.3.68.0/22205.3.68.1 to 205.3.71.254205.3.71.2551,022
211205.3.72.0/22205.3.72.1 to 205.3.75.254205.3.75.2551,022
212205.3.76.0/22205.3.76.1 to 205.3.79.254205.3.79.2551,022
213205.3.80.0/22205.3.80.1 to 205.3.83.254205.3.83.2551,022
214205.3.84.0/22205.3.84.1 to 205.3.87.254205.3.87.2551,022
215205.3.88.0/22205.3.88.1 to 205.3.91.254205.3.91.2551,022
216205.3.92.0/22205.3.92.1 to 205.3.95.254205.3.95.2551,022
217205.3.96.0/22205.3.96.1 to 205.3.99.254205.3.99.2551,022
218205.3.100.0/22205.3.100.1 to 205.3.103.254205.3.103.2551,022
219205.3.104.0/22205.3.104.1 to 205.3.107.254205.3.107.2551,022
220205.3.108.0/22205.3.108.1 to 205.3.111.254205.3.111.2551,022
221205.3.112.0/22205.3.112.1 to 205.3.115.254205.3.115.2551,022
222205.3.116.0/22205.3.116.1 to 205.3.119.254205.3.119.2551,022
223205.3.120.0/22205.3.120.1 to 205.3.123.254205.3.123.2551,022
224205.3.124.0/22205.3.124.1 to 205.3.127.254205.3.127.2551,022
225205.3.128.0/22205.3.128.1 to 205.3.131.254205.3.131.2551,022
226205.3.132.0/22205.3.132.1 to 205.3.135.254205.3.135.2551,022
227205.3.136.0/22205.3.136.1 to 205.3.139.254205.3.139.2551,022
228205.3.140.0/22205.3.140.1 to 205.3.143.254205.3.143.2551,022
229205.3.144.0/22205.3.144.1 to 205.3.147.254205.3.147.2551,022
230205.3.148.0/22205.3.148.1 to 205.3.151.254205.3.151.2551,022
231205.3.152.0/22205.3.152.1 to 205.3.155.254205.3.155.2551,022
232205.3.156.0/22205.3.156.1 to 205.3.159.254205.3.159.2551,022
233205.3.160.0/22205.3.160.1 to 205.3.163.254205.3.163.2551,022
234205.3.164.0/22205.3.164.1 to 205.3.167.254205.3.167.2551,022
235205.3.168.0/22205.3.168.1 to 205.3.171.254205.3.171.2551,022
236205.3.172.0/22205.3.172.1 to 205.3.175.254205.3.175.2551,022
237205.3.176.0/22205.3.176.1 to 205.3.179.254205.3.179.2551,022
238205.3.180.0/22205.3.180.1 to 205.3.183.254205.3.183.2551,022
239205.3.184.0/22205.3.184.1 to 205.3.187.254205.3.187.2551,022
240205.3.188.0/22205.3.188.1 to 205.3.191.254205.3.191.2551,022
241205.3.192.0/22205.3.192.1 to 205.3.195.254205.3.195.2551,022
242205.3.196.0/22205.3.196.1 to 205.3.199.254205.3.199.2551,022
243205.3.200.0/22205.3.200.1 to 205.3.203.254205.3.203.2551,022
244205.3.204.0/22205.3.204.1 to 205.3.207.254205.3.207.2551,022
245205.3.208.0/22205.3.208.1 to 205.3.211.254205.3.211.2551,022
246205.3.212.0/22205.3.212.1 to 205.3.215.254205.3.215.2551,022
247205.3.216.0/22205.3.216.1 to 205.3.219.254205.3.219.2551,022
248205.3.220.0/22205.3.220.1 to 205.3.223.254205.3.223.2551,022
249205.3.224.0/22205.3.224.1 to 205.3.227.254205.3.227.2551,022
250205.3.228.0/22205.3.228.1 to 205.3.231.254205.3.231.2551,022
251205.3.232.0/22205.3.232.1 to 205.3.235.254205.3.235.2551,022
252205.3.236.0/22205.3.236.1 to 205.3.239.254205.3.239.2551,022
253205.3.240.0/22205.3.240.1 to 205.3.243.254205.3.243.2551,022
254205.3.244.0/22205.3.244.1 to 205.3.247.254205.3.247.2551,022
255205.3.248.0/22205.3.248.1 to 205.3.251.254205.3.251.2551,022
256205.3.252.0/22205.3.252.1 to 205.3.255.254205.3.255.2551,022

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.