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.

Network247.136.0.0/13
Usable hosts524,286
Subnet mask255.248.0.0
Addresses524,288
Network address
247.136.0.0
Broadcast address
247.143.255.255
First usable
247.136.0.1
Last usable
247.143.255.254
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
Reserved 240.0.0.0/4
Future use; not usable on most systems
Old class
E (reserved)
As numbers
Hex F7880000 · Integer 4152885248 to 4153409535
Reverse DNS zones
136.247.in-addr.arpa
137.247.in-addr.arpa
138.247.in-addr.arpa
139.247.in-addr.arpa
140.247.in-addr.arpa
141.247.in-addr.arpa
142.247.in-addr.arpa
143.247.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
Address11110111.10001000.00000000.00000000247.136.0.0
Subnet mask11111111.11111000.00000000.00000000255.248.0.0
Network11110111.10001000.00000000.00000000247.136.0.0
Broadcast11110111.10001111.11111111.11111111247.143.255.255
Split into smaller subnets/25
/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)

247.136.0.0/13 makes 4,096 subnets of /25; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1247.136.0.0/25247.136.0.1 to 247.136.0.126247.136.0.127126
2247.136.0.128/25247.136.0.129 to 247.136.0.254247.136.0.255126
3247.136.1.0/25247.136.1.1 to 247.136.1.126247.136.1.127126
4247.136.1.128/25247.136.1.129 to 247.136.1.254247.136.1.255126
5247.136.2.0/25247.136.2.1 to 247.136.2.126247.136.2.127126
6247.136.2.128/25247.136.2.129 to 247.136.2.254247.136.2.255126
7247.136.3.0/25247.136.3.1 to 247.136.3.126247.136.3.127126
8247.136.3.128/25247.136.3.129 to 247.136.3.254247.136.3.255126
9247.136.4.0/25247.136.4.1 to 247.136.4.126247.136.4.127126
10247.136.4.128/25247.136.4.129 to 247.136.4.254247.136.4.255126
11247.136.5.0/25247.136.5.1 to 247.136.5.126247.136.5.127126
12247.136.5.128/25247.136.5.129 to 247.136.5.254247.136.5.255126
13247.136.6.0/25247.136.6.1 to 247.136.6.126247.136.6.127126
14247.136.6.128/25247.136.6.129 to 247.136.6.254247.136.6.255126
15247.136.7.0/25247.136.7.1 to 247.136.7.126247.136.7.127126
16247.136.7.128/25247.136.7.129 to 247.136.7.254247.136.7.255126
17247.136.8.0/25247.136.8.1 to 247.136.8.126247.136.8.127126
18247.136.8.128/25247.136.8.129 to 247.136.8.254247.136.8.255126
19247.136.9.0/25247.136.9.1 to 247.136.9.126247.136.9.127126
20247.136.9.128/25247.136.9.129 to 247.136.9.254247.136.9.255126
21247.136.10.0/25247.136.10.1 to 247.136.10.126247.136.10.127126
22247.136.10.128/25247.136.10.129 to 247.136.10.254247.136.10.255126
23247.136.11.0/25247.136.11.1 to 247.136.11.126247.136.11.127126
24247.136.11.128/25247.136.11.129 to 247.136.11.254247.136.11.255126
25247.136.12.0/25247.136.12.1 to 247.136.12.126247.136.12.127126
26247.136.12.128/25247.136.12.129 to 247.136.12.254247.136.12.255126
27247.136.13.0/25247.136.13.1 to 247.136.13.126247.136.13.127126
28247.136.13.128/25247.136.13.129 to 247.136.13.254247.136.13.255126
29247.136.14.0/25247.136.14.1 to 247.136.14.126247.136.14.127126
30247.136.14.128/25247.136.14.129 to 247.136.14.254247.136.14.255126
31247.136.15.0/25247.136.15.1 to 247.136.15.126247.136.15.127126
32247.136.15.128/25247.136.15.129 to 247.136.15.254247.136.15.255126
33247.136.16.0/25247.136.16.1 to 247.136.16.126247.136.16.127126
34247.136.16.128/25247.136.16.129 to 247.136.16.254247.136.16.255126
35247.136.17.0/25247.136.17.1 to 247.136.17.126247.136.17.127126
36247.136.17.128/25247.136.17.129 to 247.136.17.254247.136.17.255126
37247.136.18.0/25247.136.18.1 to 247.136.18.126247.136.18.127126
38247.136.18.128/25247.136.18.129 to 247.136.18.254247.136.18.255126
39247.136.19.0/25247.136.19.1 to 247.136.19.126247.136.19.127126
40247.136.19.128/25247.136.19.129 to 247.136.19.254247.136.19.255126
41247.136.20.0/25247.136.20.1 to 247.136.20.126247.136.20.127126
42247.136.20.128/25247.136.20.129 to 247.136.20.254247.136.20.255126
43247.136.21.0/25247.136.21.1 to 247.136.21.126247.136.21.127126
44247.136.21.128/25247.136.21.129 to 247.136.21.254247.136.21.255126
45247.136.22.0/25247.136.22.1 to 247.136.22.126247.136.22.127126
46247.136.22.128/25247.136.22.129 to 247.136.22.254247.136.22.255126
47247.136.23.0/25247.136.23.1 to 247.136.23.126247.136.23.127126
48247.136.23.128/25247.136.23.129 to 247.136.23.254247.136.23.255126
49247.136.24.0/25247.136.24.1 to 247.136.24.126247.136.24.127126
50247.136.24.128/25247.136.24.129 to 247.136.24.254247.136.24.255126
51247.136.25.0/25247.136.25.1 to 247.136.25.126247.136.25.127126
52247.136.25.128/25247.136.25.129 to 247.136.25.254247.136.25.255126
53247.136.26.0/25247.136.26.1 to 247.136.26.126247.136.26.127126
54247.136.26.128/25247.136.26.129 to 247.136.26.254247.136.26.255126
55247.136.27.0/25247.136.27.1 to 247.136.27.126247.136.27.127126
56247.136.27.128/25247.136.27.129 to 247.136.27.254247.136.27.255126
57247.136.28.0/25247.136.28.1 to 247.136.28.126247.136.28.127126
58247.136.28.128/25247.136.28.129 to 247.136.28.254247.136.28.255126
59247.136.29.0/25247.136.29.1 to 247.136.29.126247.136.29.127126
60247.136.29.128/25247.136.29.129 to 247.136.29.254247.136.29.255126
61247.136.30.0/25247.136.30.1 to 247.136.30.126247.136.30.127126
62247.136.30.128/25247.136.30.129 to 247.136.30.254247.136.30.255126
63247.136.31.0/25247.136.31.1 to 247.136.31.126247.136.31.127126
64247.136.31.128/25247.136.31.129 to 247.136.31.254247.136.31.255126
65247.136.32.0/25247.136.32.1 to 247.136.32.126247.136.32.127126
66247.136.32.128/25247.136.32.129 to 247.136.32.254247.136.32.255126
67247.136.33.0/25247.136.33.1 to 247.136.33.126247.136.33.127126
68247.136.33.128/25247.136.33.129 to 247.136.33.254247.136.33.255126
69247.136.34.0/25247.136.34.1 to 247.136.34.126247.136.34.127126
70247.136.34.128/25247.136.34.129 to 247.136.34.254247.136.34.255126
71247.136.35.0/25247.136.35.1 to 247.136.35.126247.136.35.127126
72247.136.35.128/25247.136.35.129 to 247.136.35.254247.136.35.255126
73247.136.36.0/25247.136.36.1 to 247.136.36.126247.136.36.127126
74247.136.36.128/25247.136.36.129 to 247.136.36.254247.136.36.255126
75247.136.37.0/25247.136.37.1 to 247.136.37.126247.136.37.127126
76247.136.37.128/25247.136.37.129 to 247.136.37.254247.136.37.255126
77247.136.38.0/25247.136.38.1 to 247.136.38.126247.136.38.127126
78247.136.38.128/25247.136.38.129 to 247.136.38.254247.136.38.255126
79247.136.39.0/25247.136.39.1 to 247.136.39.126247.136.39.127126
80247.136.39.128/25247.136.39.129 to 247.136.39.254247.136.39.255126
81247.136.40.0/25247.136.40.1 to 247.136.40.126247.136.40.127126
82247.136.40.128/25247.136.40.129 to 247.136.40.254247.136.40.255126
83247.136.41.0/25247.136.41.1 to 247.136.41.126247.136.41.127126
84247.136.41.128/25247.136.41.129 to 247.136.41.254247.136.41.255126
85247.136.42.0/25247.136.42.1 to 247.136.42.126247.136.42.127126
86247.136.42.128/25247.136.42.129 to 247.136.42.254247.136.42.255126
87247.136.43.0/25247.136.43.1 to 247.136.43.126247.136.43.127126
88247.136.43.128/25247.136.43.129 to 247.136.43.254247.136.43.255126
89247.136.44.0/25247.136.44.1 to 247.136.44.126247.136.44.127126
90247.136.44.128/25247.136.44.129 to 247.136.44.254247.136.44.255126
91247.136.45.0/25247.136.45.1 to 247.136.45.126247.136.45.127126
92247.136.45.128/25247.136.45.129 to 247.136.45.254247.136.45.255126
93247.136.46.0/25247.136.46.1 to 247.136.46.126247.136.46.127126
94247.136.46.128/25247.136.46.129 to 247.136.46.254247.136.46.255126
95247.136.47.0/25247.136.47.1 to 247.136.47.126247.136.47.127126
96247.136.47.128/25247.136.47.129 to 247.136.47.254247.136.47.255126
97247.136.48.0/25247.136.48.1 to 247.136.48.126247.136.48.127126
98247.136.48.128/25247.136.48.129 to 247.136.48.254247.136.48.255126
99247.136.49.0/25247.136.49.1 to 247.136.49.126247.136.49.127126
100247.136.49.128/25247.136.49.129 to 247.136.49.254247.136.49.255126
101247.136.50.0/25247.136.50.1 to 247.136.50.126247.136.50.127126
102247.136.50.128/25247.136.50.129 to 247.136.50.254247.136.50.255126
103247.136.51.0/25247.136.51.1 to 247.136.51.126247.136.51.127126
104247.136.51.128/25247.136.51.129 to 247.136.51.254247.136.51.255126
105247.136.52.0/25247.136.52.1 to 247.136.52.126247.136.52.127126
106247.136.52.128/25247.136.52.129 to 247.136.52.254247.136.52.255126
107247.136.53.0/25247.136.53.1 to 247.136.53.126247.136.53.127126
108247.136.53.128/25247.136.53.129 to 247.136.53.254247.136.53.255126
109247.136.54.0/25247.136.54.1 to 247.136.54.126247.136.54.127126
110247.136.54.128/25247.136.54.129 to 247.136.54.254247.136.54.255126
111247.136.55.0/25247.136.55.1 to 247.136.55.126247.136.55.127126
112247.136.55.128/25247.136.55.129 to 247.136.55.254247.136.55.255126
113247.136.56.0/25247.136.56.1 to 247.136.56.126247.136.56.127126
114247.136.56.128/25247.136.56.129 to 247.136.56.254247.136.56.255126
115247.136.57.0/25247.136.57.1 to 247.136.57.126247.136.57.127126
116247.136.57.128/25247.136.57.129 to 247.136.57.254247.136.57.255126
117247.136.58.0/25247.136.58.1 to 247.136.58.126247.136.58.127126
118247.136.58.128/25247.136.58.129 to 247.136.58.254247.136.58.255126
119247.136.59.0/25247.136.59.1 to 247.136.59.126247.136.59.127126
120247.136.59.128/25247.136.59.129 to 247.136.59.254247.136.59.255126
121247.136.60.0/25247.136.60.1 to 247.136.60.126247.136.60.127126
122247.136.60.128/25247.136.60.129 to 247.136.60.254247.136.60.255126
123247.136.61.0/25247.136.61.1 to 247.136.61.126247.136.61.127126
124247.136.61.128/25247.136.61.129 to 247.136.61.254247.136.61.255126
125247.136.62.0/25247.136.62.1 to 247.136.62.126247.136.62.127126
126247.136.62.128/25247.136.62.129 to 247.136.62.254247.136.62.255126
127247.136.63.0/25247.136.63.1 to 247.136.63.126247.136.63.127126
128247.136.63.128/25247.136.63.129 to 247.136.63.254247.136.63.255126
129247.136.64.0/25247.136.64.1 to 247.136.64.126247.136.64.127126
130247.136.64.128/25247.136.64.129 to 247.136.64.254247.136.64.255126
131247.136.65.0/25247.136.65.1 to 247.136.65.126247.136.65.127126
132247.136.65.128/25247.136.65.129 to 247.136.65.254247.136.65.255126
133247.136.66.0/25247.136.66.1 to 247.136.66.126247.136.66.127126
134247.136.66.128/25247.136.66.129 to 247.136.66.254247.136.66.255126
135247.136.67.0/25247.136.67.1 to 247.136.67.126247.136.67.127126
136247.136.67.128/25247.136.67.129 to 247.136.67.254247.136.67.255126
137247.136.68.0/25247.136.68.1 to 247.136.68.126247.136.68.127126
138247.136.68.128/25247.136.68.129 to 247.136.68.254247.136.68.255126
139247.136.69.0/25247.136.69.1 to 247.136.69.126247.136.69.127126
140247.136.69.128/25247.136.69.129 to 247.136.69.254247.136.69.255126
141247.136.70.0/25247.136.70.1 to 247.136.70.126247.136.70.127126
142247.136.70.128/25247.136.70.129 to 247.136.70.254247.136.70.255126
143247.136.71.0/25247.136.71.1 to 247.136.71.126247.136.71.127126
144247.136.71.128/25247.136.71.129 to 247.136.71.254247.136.71.255126
145247.136.72.0/25247.136.72.1 to 247.136.72.126247.136.72.127126
146247.136.72.128/25247.136.72.129 to 247.136.72.254247.136.72.255126
147247.136.73.0/25247.136.73.1 to 247.136.73.126247.136.73.127126
148247.136.73.128/25247.136.73.129 to 247.136.73.254247.136.73.255126
149247.136.74.0/25247.136.74.1 to 247.136.74.126247.136.74.127126
150247.136.74.128/25247.136.74.129 to 247.136.74.254247.136.74.255126
151247.136.75.0/25247.136.75.1 to 247.136.75.126247.136.75.127126
152247.136.75.128/25247.136.75.129 to 247.136.75.254247.136.75.255126
153247.136.76.0/25247.136.76.1 to 247.136.76.126247.136.76.127126
154247.136.76.128/25247.136.76.129 to 247.136.76.254247.136.76.255126
155247.136.77.0/25247.136.77.1 to 247.136.77.126247.136.77.127126
156247.136.77.128/25247.136.77.129 to 247.136.77.254247.136.77.255126
157247.136.78.0/25247.136.78.1 to 247.136.78.126247.136.78.127126
158247.136.78.128/25247.136.78.129 to 247.136.78.254247.136.78.255126
159247.136.79.0/25247.136.79.1 to 247.136.79.126247.136.79.127126
160247.136.79.128/25247.136.79.129 to 247.136.79.254247.136.79.255126
161247.136.80.0/25247.136.80.1 to 247.136.80.126247.136.80.127126
162247.136.80.128/25247.136.80.129 to 247.136.80.254247.136.80.255126
163247.136.81.0/25247.136.81.1 to 247.136.81.126247.136.81.127126
164247.136.81.128/25247.136.81.129 to 247.136.81.254247.136.81.255126
165247.136.82.0/25247.136.82.1 to 247.136.82.126247.136.82.127126
166247.136.82.128/25247.136.82.129 to 247.136.82.254247.136.82.255126
167247.136.83.0/25247.136.83.1 to 247.136.83.126247.136.83.127126
168247.136.83.128/25247.136.83.129 to 247.136.83.254247.136.83.255126
169247.136.84.0/25247.136.84.1 to 247.136.84.126247.136.84.127126
170247.136.84.128/25247.136.84.129 to 247.136.84.254247.136.84.255126
171247.136.85.0/25247.136.85.1 to 247.136.85.126247.136.85.127126
172247.136.85.128/25247.136.85.129 to 247.136.85.254247.136.85.255126
173247.136.86.0/25247.136.86.1 to 247.136.86.126247.136.86.127126
174247.136.86.128/25247.136.86.129 to 247.136.86.254247.136.86.255126
175247.136.87.0/25247.136.87.1 to 247.136.87.126247.136.87.127126
176247.136.87.128/25247.136.87.129 to 247.136.87.254247.136.87.255126
177247.136.88.0/25247.136.88.1 to 247.136.88.126247.136.88.127126
178247.136.88.128/25247.136.88.129 to 247.136.88.254247.136.88.255126
179247.136.89.0/25247.136.89.1 to 247.136.89.126247.136.89.127126
180247.136.89.128/25247.136.89.129 to 247.136.89.254247.136.89.255126
181247.136.90.0/25247.136.90.1 to 247.136.90.126247.136.90.127126
182247.136.90.128/25247.136.90.129 to 247.136.90.254247.136.90.255126
183247.136.91.0/25247.136.91.1 to 247.136.91.126247.136.91.127126
184247.136.91.128/25247.136.91.129 to 247.136.91.254247.136.91.255126
185247.136.92.0/25247.136.92.1 to 247.136.92.126247.136.92.127126
186247.136.92.128/25247.136.92.129 to 247.136.92.254247.136.92.255126
187247.136.93.0/25247.136.93.1 to 247.136.93.126247.136.93.127126
188247.136.93.128/25247.136.93.129 to 247.136.93.254247.136.93.255126
189247.136.94.0/25247.136.94.1 to 247.136.94.126247.136.94.127126
190247.136.94.128/25247.136.94.129 to 247.136.94.254247.136.94.255126
191247.136.95.0/25247.136.95.1 to 247.136.95.126247.136.95.127126
192247.136.95.128/25247.136.95.129 to 247.136.95.254247.136.95.255126
193247.136.96.0/25247.136.96.1 to 247.136.96.126247.136.96.127126
194247.136.96.128/25247.136.96.129 to 247.136.96.254247.136.96.255126
195247.136.97.0/25247.136.97.1 to 247.136.97.126247.136.97.127126
196247.136.97.128/25247.136.97.129 to 247.136.97.254247.136.97.255126
197247.136.98.0/25247.136.98.1 to 247.136.98.126247.136.98.127126
198247.136.98.128/25247.136.98.129 to 247.136.98.254247.136.98.255126
199247.136.99.0/25247.136.99.1 to 247.136.99.126247.136.99.127126
200247.136.99.128/25247.136.99.129 to 247.136.99.254247.136.99.255126
201247.136.100.0/25247.136.100.1 to 247.136.100.126247.136.100.127126
202247.136.100.128/25247.136.100.129 to 247.136.100.254247.136.100.255126
203247.136.101.0/25247.136.101.1 to 247.136.101.126247.136.101.127126
204247.136.101.128/25247.136.101.129 to 247.136.101.254247.136.101.255126
205247.136.102.0/25247.136.102.1 to 247.136.102.126247.136.102.127126
206247.136.102.128/25247.136.102.129 to 247.136.102.254247.136.102.255126
207247.136.103.0/25247.136.103.1 to 247.136.103.126247.136.103.127126
208247.136.103.128/25247.136.103.129 to 247.136.103.254247.136.103.255126
209247.136.104.0/25247.136.104.1 to 247.136.104.126247.136.104.127126
210247.136.104.128/25247.136.104.129 to 247.136.104.254247.136.104.255126
211247.136.105.0/25247.136.105.1 to 247.136.105.126247.136.105.127126
212247.136.105.128/25247.136.105.129 to 247.136.105.254247.136.105.255126
213247.136.106.0/25247.136.106.1 to 247.136.106.126247.136.106.127126
214247.136.106.128/25247.136.106.129 to 247.136.106.254247.136.106.255126
215247.136.107.0/25247.136.107.1 to 247.136.107.126247.136.107.127126
216247.136.107.128/25247.136.107.129 to 247.136.107.254247.136.107.255126
217247.136.108.0/25247.136.108.1 to 247.136.108.126247.136.108.127126
218247.136.108.128/25247.136.108.129 to 247.136.108.254247.136.108.255126
219247.136.109.0/25247.136.109.1 to 247.136.109.126247.136.109.127126
220247.136.109.128/25247.136.109.129 to 247.136.109.254247.136.109.255126
221247.136.110.0/25247.136.110.1 to 247.136.110.126247.136.110.127126
222247.136.110.128/25247.136.110.129 to 247.136.110.254247.136.110.255126
223247.136.111.0/25247.136.111.1 to 247.136.111.126247.136.111.127126
224247.136.111.128/25247.136.111.129 to 247.136.111.254247.136.111.255126
225247.136.112.0/25247.136.112.1 to 247.136.112.126247.136.112.127126
226247.136.112.128/25247.136.112.129 to 247.136.112.254247.136.112.255126
227247.136.113.0/25247.136.113.1 to 247.136.113.126247.136.113.127126
228247.136.113.128/25247.136.113.129 to 247.136.113.254247.136.113.255126
229247.136.114.0/25247.136.114.1 to 247.136.114.126247.136.114.127126
230247.136.114.128/25247.136.114.129 to 247.136.114.254247.136.114.255126
231247.136.115.0/25247.136.115.1 to 247.136.115.126247.136.115.127126
232247.136.115.128/25247.136.115.129 to 247.136.115.254247.136.115.255126
233247.136.116.0/25247.136.116.1 to 247.136.116.126247.136.116.127126
234247.136.116.128/25247.136.116.129 to 247.136.116.254247.136.116.255126
235247.136.117.0/25247.136.117.1 to 247.136.117.126247.136.117.127126
236247.136.117.128/25247.136.117.129 to 247.136.117.254247.136.117.255126
237247.136.118.0/25247.136.118.1 to 247.136.118.126247.136.118.127126
238247.136.118.128/25247.136.118.129 to 247.136.118.254247.136.118.255126
239247.136.119.0/25247.136.119.1 to 247.136.119.126247.136.119.127126
240247.136.119.128/25247.136.119.129 to 247.136.119.254247.136.119.255126
241247.136.120.0/25247.136.120.1 to 247.136.120.126247.136.120.127126
242247.136.120.128/25247.136.120.129 to 247.136.120.254247.136.120.255126
243247.136.121.0/25247.136.121.1 to 247.136.121.126247.136.121.127126
244247.136.121.128/25247.136.121.129 to 247.136.121.254247.136.121.255126
245247.136.122.0/25247.136.122.1 to 247.136.122.126247.136.122.127126
246247.136.122.128/25247.136.122.129 to 247.136.122.254247.136.122.255126
247247.136.123.0/25247.136.123.1 to 247.136.123.126247.136.123.127126
248247.136.123.128/25247.136.123.129 to 247.136.123.254247.136.123.255126
249247.136.124.0/25247.136.124.1 to 247.136.124.126247.136.124.127126
250247.136.124.128/25247.136.124.129 to 247.136.124.254247.136.124.255126
251247.136.125.0/25247.136.125.1 to 247.136.125.126247.136.125.127126
252247.136.125.128/25247.136.125.129 to 247.136.125.254247.136.125.255126
253247.136.126.0/25247.136.126.1 to 247.136.126.126247.136.126.127126
254247.136.126.128/25247.136.126.129 to 247.136.126.254247.136.126.255126
255247.136.127.0/25247.136.127.1 to 247.136.127.126247.136.127.127126
256247.136.127.128/25247.136.127.129 to 247.136.127.254247.136.127.255126

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.