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.

Network165.136.0.0/13
Usable hosts524,286
Subnet mask255.248.0.0
Addresses524,288
Network address
165.136.0.0
Broadcast address
165.143.255.255
First usable
165.136.0.1
Last usable
165.143.255.254
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
B (default /16)
As numbers
Hex A5880000 · Integer 2777153536 to 2777677823
Reverse DNS zones
136.165.in-addr.arpa
137.165.in-addr.arpa
138.165.in-addr.arpa
139.165.in-addr.arpa
140.165.in-addr.arpa
141.165.in-addr.arpa
142.165.in-addr.arpa
143.165.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
Address10100101.10001000.00000000.00000000165.136.0.0
Subnet mask11111111.11111000.00000000.00000000255.248.0.0
Network10100101.10001000.00000000.00000000165.136.0.0
Broadcast10100101.10001111.11111111.11111111165.143.255.255
Split into smaller subnets/24
/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)

165.136.0.0/13 makes 2,048 subnets of /24; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1165.136.0.0/24165.136.0.1 to 165.136.0.254165.136.0.255254
2165.136.1.0/24165.136.1.1 to 165.136.1.254165.136.1.255254
3165.136.2.0/24165.136.2.1 to 165.136.2.254165.136.2.255254
4165.136.3.0/24165.136.3.1 to 165.136.3.254165.136.3.255254
5165.136.4.0/24165.136.4.1 to 165.136.4.254165.136.4.255254
6165.136.5.0/24165.136.5.1 to 165.136.5.254165.136.5.255254
7165.136.6.0/24165.136.6.1 to 165.136.6.254165.136.6.255254
8165.136.7.0/24165.136.7.1 to 165.136.7.254165.136.7.255254
9165.136.8.0/24165.136.8.1 to 165.136.8.254165.136.8.255254
10165.136.9.0/24165.136.9.1 to 165.136.9.254165.136.9.255254
11165.136.10.0/24165.136.10.1 to 165.136.10.254165.136.10.255254
12165.136.11.0/24165.136.11.1 to 165.136.11.254165.136.11.255254
13165.136.12.0/24165.136.12.1 to 165.136.12.254165.136.12.255254
14165.136.13.0/24165.136.13.1 to 165.136.13.254165.136.13.255254
15165.136.14.0/24165.136.14.1 to 165.136.14.254165.136.14.255254
16165.136.15.0/24165.136.15.1 to 165.136.15.254165.136.15.255254
17165.136.16.0/24165.136.16.1 to 165.136.16.254165.136.16.255254
18165.136.17.0/24165.136.17.1 to 165.136.17.254165.136.17.255254
19165.136.18.0/24165.136.18.1 to 165.136.18.254165.136.18.255254
20165.136.19.0/24165.136.19.1 to 165.136.19.254165.136.19.255254
21165.136.20.0/24165.136.20.1 to 165.136.20.254165.136.20.255254
22165.136.21.0/24165.136.21.1 to 165.136.21.254165.136.21.255254
23165.136.22.0/24165.136.22.1 to 165.136.22.254165.136.22.255254
24165.136.23.0/24165.136.23.1 to 165.136.23.254165.136.23.255254
25165.136.24.0/24165.136.24.1 to 165.136.24.254165.136.24.255254
26165.136.25.0/24165.136.25.1 to 165.136.25.254165.136.25.255254
27165.136.26.0/24165.136.26.1 to 165.136.26.254165.136.26.255254
28165.136.27.0/24165.136.27.1 to 165.136.27.254165.136.27.255254
29165.136.28.0/24165.136.28.1 to 165.136.28.254165.136.28.255254
30165.136.29.0/24165.136.29.1 to 165.136.29.254165.136.29.255254
31165.136.30.0/24165.136.30.1 to 165.136.30.254165.136.30.255254
32165.136.31.0/24165.136.31.1 to 165.136.31.254165.136.31.255254
33165.136.32.0/24165.136.32.1 to 165.136.32.254165.136.32.255254
34165.136.33.0/24165.136.33.1 to 165.136.33.254165.136.33.255254
35165.136.34.0/24165.136.34.1 to 165.136.34.254165.136.34.255254
36165.136.35.0/24165.136.35.1 to 165.136.35.254165.136.35.255254
37165.136.36.0/24165.136.36.1 to 165.136.36.254165.136.36.255254
38165.136.37.0/24165.136.37.1 to 165.136.37.254165.136.37.255254
39165.136.38.0/24165.136.38.1 to 165.136.38.254165.136.38.255254
40165.136.39.0/24165.136.39.1 to 165.136.39.254165.136.39.255254
41165.136.40.0/24165.136.40.1 to 165.136.40.254165.136.40.255254
42165.136.41.0/24165.136.41.1 to 165.136.41.254165.136.41.255254
43165.136.42.0/24165.136.42.1 to 165.136.42.254165.136.42.255254
44165.136.43.0/24165.136.43.1 to 165.136.43.254165.136.43.255254
45165.136.44.0/24165.136.44.1 to 165.136.44.254165.136.44.255254
46165.136.45.0/24165.136.45.1 to 165.136.45.254165.136.45.255254
47165.136.46.0/24165.136.46.1 to 165.136.46.254165.136.46.255254
48165.136.47.0/24165.136.47.1 to 165.136.47.254165.136.47.255254
49165.136.48.0/24165.136.48.1 to 165.136.48.254165.136.48.255254
50165.136.49.0/24165.136.49.1 to 165.136.49.254165.136.49.255254
51165.136.50.0/24165.136.50.1 to 165.136.50.254165.136.50.255254
52165.136.51.0/24165.136.51.1 to 165.136.51.254165.136.51.255254
53165.136.52.0/24165.136.52.1 to 165.136.52.254165.136.52.255254
54165.136.53.0/24165.136.53.1 to 165.136.53.254165.136.53.255254
55165.136.54.0/24165.136.54.1 to 165.136.54.254165.136.54.255254
56165.136.55.0/24165.136.55.1 to 165.136.55.254165.136.55.255254
57165.136.56.0/24165.136.56.1 to 165.136.56.254165.136.56.255254
58165.136.57.0/24165.136.57.1 to 165.136.57.254165.136.57.255254
59165.136.58.0/24165.136.58.1 to 165.136.58.254165.136.58.255254
60165.136.59.0/24165.136.59.1 to 165.136.59.254165.136.59.255254
61165.136.60.0/24165.136.60.1 to 165.136.60.254165.136.60.255254
62165.136.61.0/24165.136.61.1 to 165.136.61.254165.136.61.255254
63165.136.62.0/24165.136.62.1 to 165.136.62.254165.136.62.255254
64165.136.63.0/24165.136.63.1 to 165.136.63.254165.136.63.255254
65165.136.64.0/24165.136.64.1 to 165.136.64.254165.136.64.255254
66165.136.65.0/24165.136.65.1 to 165.136.65.254165.136.65.255254
67165.136.66.0/24165.136.66.1 to 165.136.66.254165.136.66.255254
68165.136.67.0/24165.136.67.1 to 165.136.67.254165.136.67.255254
69165.136.68.0/24165.136.68.1 to 165.136.68.254165.136.68.255254
70165.136.69.0/24165.136.69.1 to 165.136.69.254165.136.69.255254
71165.136.70.0/24165.136.70.1 to 165.136.70.254165.136.70.255254
72165.136.71.0/24165.136.71.1 to 165.136.71.254165.136.71.255254
73165.136.72.0/24165.136.72.1 to 165.136.72.254165.136.72.255254
74165.136.73.0/24165.136.73.1 to 165.136.73.254165.136.73.255254
75165.136.74.0/24165.136.74.1 to 165.136.74.254165.136.74.255254
76165.136.75.0/24165.136.75.1 to 165.136.75.254165.136.75.255254
77165.136.76.0/24165.136.76.1 to 165.136.76.254165.136.76.255254
78165.136.77.0/24165.136.77.1 to 165.136.77.254165.136.77.255254
79165.136.78.0/24165.136.78.1 to 165.136.78.254165.136.78.255254
80165.136.79.0/24165.136.79.1 to 165.136.79.254165.136.79.255254
81165.136.80.0/24165.136.80.1 to 165.136.80.254165.136.80.255254
82165.136.81.0/24165.136.81.1 to 165.136.81.254165.136.81.255254
83165.136.82.0/24165.136.82.1 to 165.136.82.254165.136.82.255254
84165.136.83.0/24165.136.83.1 to 165.136.83.254165.136.83.255254
85165.136.84.0/24165.136.84.1 to 165.136.84.254165.136.84.255254
86165.136.85.0/24165.136.85.1 to 165.136.85.254165.136.85.255254
87165.136.86.0/24165.136.86.1 to 165.136.86.254165.136.86.255254
88165.136.87.0/24165.136.87.1 to 165.136.87.254165.136.87.255254
89165.136.88.0/24165.136.88.1 to 165.136.88.254165.136.88.255254
90165.136.89.0/24165.136.89.1 to 165.136.89.254165.136.89.255254
91165.136.90.0/24165.136.90.1 to 165.136.90.254165.136.90.255254
92165.136.91.0/24165.136.91.1 to 165.136.91.254165.136.91.255254
93165.136.92.0/24165.136.92.1 to 165.136.92.254165.136.92.255254
94165.136.93.0/24165.136.93.1 to 165.136.93.254165.136.93.255254
95165.136.94.0/24165.136.94.1 to 165.136.94.254165.136.94.255254
96165.136.95.0/24165.136.95.1 to 165.136.95.254165.136.95.255254
97165.136.96.0/24165.136.96.1 to 165.136.96.254165.136.96.255254
98165.136.97.0/24165.136.97.1 to 165.136.97.254165.136.97.255254
99165.136.98.0/24165.136.98.1 to 165.136.98.254165.136.98.255254
100165.136.99.0/24165.136.99.1 to 165.136.99.254165.136.99.255254
101165.136.100.0/24165.136.100.1 to 165.136.100.254165.136.100.255254
102165.136.101.0/24165.136.101.1 to 165.136.101.254165.136.101.255254
103165.136.102.0/24165.136.102.1 to 165.136.102.254165.136.102.255254
104165.136.103.0/24165.136.103.1 to 165.136.103.254165.136.103.255254
105165.136.104.0/24165.136.104.1 to 165.136.104.254165.136.104.255254
106165.136.105.0/24165.136.105.1 to 165.136.105.254165.136.105.255254
107165.136.106.0/24165.136.106.1 to 165.136.106.254165.136.106.255254
108165.136.107.0/24165.136.107.1 to 165.136.107.254165.136.107.255254
109165.136.108.0/24165.136.108.1 to 165.136.108.254165.136.108.255254
110165.136.109.0/24165.136.109.1 to 165.136.109.254165.136.109.255254
111165.136.110.0/24165.136.110.1 to 165.136.110.254165.136.110.255254
112165.136.111.0/24165.136.111.1 to 165.136.111.254165.136.111.255254
113165.136.112.0/24165.136.112.1 to 165.136.112.254165.136.112.255254
114165.136.113.0/24165.136.113.1 to 165.136.113.254165.136.113.255254
115165.136.114.0/24165.136.114.1 to 165.136.114.254165.136.114.255254
116165.136.115.0/24165.136.115.1 to 165.136.115.254165.136.115.255254
117165.136.116.0/24165.136.116.1 to 165.136.116.254165.136.116.255254
118165.136.117.0/24165.136.117.1 to 165.136.117.254165.136.117.255254
119165.136.118.0/24165.136.118.1 to 165.136.118.254165.136.118.255254
120165.136.119.0/24165.136.119.1 to 165.136.119.254165.136.119.255254
121165.136.120.0/24165.136.120.1 to 165.136.120.254165.136.120.255254
122165.136.121.0/24165.136.121.1 to 165.136.121.254165.136.121.255254
123165.136.122.0/24165.136.122.1 to 165.136.122.254165.136.122.255254
124165.136.123.0/24165.136.123.1 to 165.136.123.254165.136.123.255254
125165.136.124.0/24165.136.124.1 to 165.136.124.254165.136.124.255254
126165.136.125.0/24165.136.125.1 to 165.136.125.254165.136.125.255254
127165.136.126.0/24165.136.126.1 to 165.136.126.254165.136.126.255254
128165.136.127.0/24165.136.127.1 to 165.136.127.254165.136.127.255254
129165.136.128.0/24165.136.128.1 to 165.136.128.254165.136.128.255254
130165.136.129.0/24165.136.129.1 to 165.136.129.254165.136.129.255254
131165.136.130.0/24165.136.130.1 to 165.136.130.254165.136.130.255254
132165.136.131.0/24165.136.131.1 to 165.136.131.254165.136.131.255254
133165.136.132.0/24165.136.132.1 to 165.136.132.254165.136.132.255254
134165.136.133.0/24165.136.133.1 to 165.136.133.254165.136.133.255254
135165.136.134.0/24165.136.134.1 to 165.136.134.254165.136.134.255254
136165.136.135.0/24165.136.135.1 to 165.136.135.254165.136.135.255254
137165.136.136.0/24165.136.136.1 to 165.136.136.254165.136.136.255254
138165.136.137.0/24165.136.137.1 to 165.136.137.254165.136.137.255254
139165.136.138.0/24165.136.138.1 to 165.136.138.254165.136.138.255254
140165.136.139.0/24165.136.139.1 to 165.136.139.254165.136.139.255254
141165.136.140.0/24165.136.140.1 to 165.136.140.254165.136.140.255254
142165.136.141.0/24165.136.141.1 to 165.136.141.254165.136.141.255254
143165.136.142.0/24165.136.142.1 to 165.136.142.254165.136.142.255254
144165.136.143.0/24165.136.143.1 to 165.136.143.254165.136.143.255254
145165.136.144.0/24165.136.144.1 to 165.136.144.254165.136.144.255254
146165.136.145.0/24165.136.145.1 to 165.136.145.254165.136.145.255254
147165.136.146.0/24165.136.146.1 to 165.136.146.254165.136.146.255254
148165.136.147.0/24165.136.147.1 to 165.136.147.254165.136.147.255254
149165.136.148.0/24165.136.148.1 to 165.136.148.254165.136.148.255254
150165.136.149.0/24165.136.149.1 to 165.136.149.254165.136.149.255254
151165.136.150.0/24165.136.150.1 to 165.136.150.254165.136.150.255254
152165.136.151.0/24165.136.151.1 to 165.136.151.254165.136.151.255254
153165.136.152.0/24165.136.152.1 to 165.136.152.254165.136.152.255254
154165.136.153.0/24165.136.153.1 to 165.136.153.254165.136.153.255254
155165.136.154.0/24165.136.154.1 to 165.136.154.254165.136.154.255254
156165.136.155.0/24165.136.155.1 to 165.136.155.254165.136.155.255254
157165.136.156.0/24165.136.156.1 to 165.136.156.254165.136.156.255254
158165.136.157.0/24165.136.157.1 to 165.136.157.254165.136.157.255254
159165.136.158.0/24165.136.158.1 to 165.136.158.254165.136.158.255254
160165.136.159.0/24165.136.159.1 to 165.136.159.254165.136.159.255254
161165.136.160.0/24165.136.160.1 to 165.136.160.254165.136.160.255254
162165.136.161.0/24165.136.161.1 to 165.136.161.254165.136.161.255254
163165.136.162.0/24165.136.162.1 to 165.136.162.254165.136.162.255254
164165.136.163.0/24165.136.163.1 to 165.136.163.254165.136.163.255254
165165.136.164.0/24165.136.164.1 to 165.136.164.254165.136.164.255254
166165.136.165.0/24165.136.165.1 to 165.136.165.254165.136.165.255254
167165.136.166.0/24165.136.166.1 to 165.136.166.254165.136.166.255254
168165.136.167.0/24165.136.167.1 to 165.136.167.254165.136.167.255254
169165.136.168.0/24165.136.168.1 to 165.136.168.254165.136.168.255254
170165.136.169.0/24165.136.169.1 to 165.136.169.254165.136.169.255254
171165.136.170.0/24165.136.170.1 to 165.136.170.254165.136.170.255254
172165.136.171.0/24165.136.171.1 to 165.136.171.254165.136.171.255254
173165.136.172.0/24165.136.172.1 to 165.136.172.254165.136.172.255254
174165.136.173.0/24165.136.173.1 to 165.136.173.254165.136.173.255254
175165.136.174.0/24165.136.174.1 to 165.136.174.254165.136.174.255254
176165.136.175.0/24165.136.175.1 to 165.136.175.254165.136.175.255254
177165.136.176.0/24165.136.176.1 to 165.136.176.254165.136.176.255254
178165.136.177.0/24165.136.177.1 to 165.136.177.254165.136.177.255254
179165.136.178.0/24165.136.178.1 to 165.136.178.254165.136.178.255254
180165.136.179.0/24165.136.179.1 to 165.136.179.254165.136.179.255254
181165.136.180.0/24165.136.180.1 to 165.136.180.254165.136.180.255254
182165.136.181.0/24165.136.181.1 to 165.136.181.254165.136.181.255254
183165.136.182.0/24165.136.182.1 to 165.136.182.254165.136.182.255254
184165.136.183.0/24165.136.183.1 to 165.136.183.254165.136.183.255254
185165.136.184.0/24165.136.184.1 to 165.136.184.254165.136.184.255254
186165.136.185.0/24165.136.185.1 to 165.136.185.254165.136.185.255254
187165.136.186.0/24165.136.186.1 to 165.136.186.254165.136.186.255254
188165.136.187.0/24165.136.187.1 to 165.136.187.254165.136.187.255254
189165.136.188.0/24165.136.188.1 to 165.136.188.254165.136.188.255254
190165.136.189.0/24165.136.189.1 to 165.136.189.254165.136.189.255254
191165.136.190.0/24165.136.190.1 to 165.136.190.254165.136.190.255254
192165.136.191.0/24165.136.191.1 to 165.136.191.254165.136.191.255254
193165.136.192.0/24165.136.192.1 to 165.136.192.254165.136.192.255254
194165.136.193.0/24165.136.193.1 to 165.136.193.254165.136.193.255254
195165.136.194.0/24165.136.194.1 to 165.136.194.254165.136.194.255254
196165.136.195.0/24165.136.195.1 to 165.136.195.254165.136.195.255254
197165.136.196.0/24165.136.196.1 to 165.136.196.254165.136.196.255254
198165.136.197.0/24165.136.197.1 to 165.136.197.254165.136.197.255254
199165.136.198.0/24165.136.198.1 to 165.136.198.254165.136.198.255254
200165.136.199.0/24165.136.199.1 to 165.136.199.254165.136.199.255254
201165.136.200.0/24165.136.200.1 to 165.136.200.254165.136.200.255254
202165.136.201.0/24165.136.201.1 to 165.136.201.254165.136.201.255254
203165.136.202.0/24165.136.202.1 to 165.136.202.254165.136.202.255254
204165.136.203.0/24165.136.203.1 to 165.136.203.254165.136.203.255254
205165.136.204.0/24165.136.204.1 to 165.136.204.254165.136.204.255254
206165.136.205.0/24165.136.205.1 to 165.136.205.254165.136.205.255254
207165.136.206.0/24165.136.206.1 to 165.136.206.254165.136.206.255254
208165.136.207.0/24165.136.207.1 to 165.136.207.254165.136.207.255254
209165.136.208.0/24165.136.208.1 to 165.136.208.254165.136.208.255254
210165.136.209.0/24165.136.209.1 to 165.136.209.254165.136.209.255254
211165.136.210.0/24165.136.210.1 to 165.136.210.254165.136.210.255254
212165.136.211.0/24165.136.211.1 to 165.136.211.254165.136.211.255254
213165.136.212.0/24165.136.212.1 to 165.136.212.254165.136.212.255254
214165.136.213.0/24165.136.213.1 to 165.136.213.254165.136.213.255254
215165.136.214.0/24165.136.214.1 to 165.136.214.254165.136.214.255254
216165.136.215.0/24165.136.215.1 to 165.136.215.254165.136.215.255254
217165.136.216.0/24165.136.216.1 to 165.136.216.254165.136.216.255254
218165.136.217.0/24165.136.217.1 to 165.136.217.254165.136.217.255254
219165.136.218.0/24165.136.218.1 to 165.136.218.254165.136.218.255254
220165.136.219.0/24165.136.219.1 to 165.136.219.254165.136.219.255254
221165.136.220.0/24165.136.220.1 to 165.136.220.254165.136.220.255254
222165.136.221.0/24165.136.221.1 to 165.136.221.254165.136.221.255254
223165.136.222.0/24165.136.222.1 to 165.136.222.254165.136.222.255254
224165.136.223.0/24165.136.223.1 to 165.136.223.254165.136.223.255254
225165.136.224.0/24165.136.224.1 to 165.136.224.254165.136.224.255254
226165.136.225.0/24165.136.225.1 to 165.136.225.254165.136.225.255254
227165.136.226.0/24165.136.226.1 to 165.136.226.254165.136.226.255254
228165.136.227.0/24165.136.227.1 to 165.136.227.254165.136.227.255254
229165.136.228.0/24165.136.228.1 to 165.136.228.254165.136.228.255254
230165.136.229.0/24165.136.229.1 to 165.136.229.254165.136.229.255254
231165.136.230.0/24165.136.230.1 to 165.136.230.254165.136.230.255254
232165.136.231.0/24165.136.231.1 to 165.136.231.254165.136.231.255254
233165.136.232.0/24165.136.232.1 to 165.136.232.254165.136.232.255254
234165.136.233.0/24165.136.233.1 to 165.136.233.254165.136.233.255254
235165.136.234.0/24165.136.234.1 to 165.136.234.254165.136.234.255254
236165.136.235.0/24165.136.235.1 to 165.136.235.254165.136.235.255254
237165.136.236.0/24165.136.236.1 to 165.136.236.254165.136.236.255254
238165.136.237.0/24165.136.237.1 to 165.136.237.254165.136.237.255254
239165.136.238.0/24165.136.238.1 to 165.136.238.254165.136.238.255254
240165.136.239.0/24165.136.239.1 to 165.136.239.254165.136.239.255254
241165.136.240.0/24165.136.240.1 to 165.136.240.254165.136.240.255254
242165.136.241.0/24165.136.241.1 to 165.136.241.254165.136.241.255254
243165.136.242.0/24165.136.242.1 to 165.136.242.254165.136.242.255254
244165.136.243.0/24165.136.243.1 to 165.136.243.254165.136.243.255254
245165.136.244.0/24165.136.244.1 to 165.136.244.254165.136.244.255254
246165.136.245.0/24165.136.245.1 to 165.136.245.254165.136.245.255254
247165.136.246.0/24165.136.246.1 to 165.136.246.254165.136.246.255254
248165.136.247.0/24165.136.247.1 to 165.136.247.254165.136.247.255254
249165.136.248.0/24165.136.248.1 to 165.136.248.254165.136.248.255254
250165.136.249.0/24165.136.249.1 to 165.136.249.254165.136.249.255254
251165.136.250.0/24165.136.250.1 to 165.136.250.254165.136.250.255254
252165.136.251.0/24165.136.251.1 to 165.136.251.254165.136.251.255254
253165.136.252.0/24165.136.252.1 to 165.136.252.254165.136.252.255254
254165.136.253.0/24165.136.253.1 to 165.136.253.254165.136.253.255254
255165.136.254.0/24165.136.254.1 to 165.136.254.254165.136.254.255254
256165.136.255.0/24165.136.255.1 to 165.136.255.254165.136.255.255254

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.