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.

Network181.158.0.0/15
Usable hosts131,070
Subnet mask255.254.0.0
Addresses131,072
Network address
181.158.0.0
Broadcast address
181.159.255.255
First usable
181.158.0.1
Last usable
181.159.255.254
Usable hosts
131,070 (131,072 less the network and broadcast addresses)
Subnet mask
255.254.0.0
Wildcard mask
0.1.255.255 (Cisco ACLs, OSPF)
Prefix length
/15
Type
Public public
Old class
B (default /16)
As numbers
Hex B59E0000 · Integer 3047030784 to 3047161855
Reverse DNS zones
158.181.in-addr.arpa
159.181.in-addr.arpa
/15 is not on a 8-bit boundary, so it takes 2 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10110101.10011110.00000000.00000000181.158.0.0
Subnet mask11111111.11111110.00000000.00000000255.254.0.0
Network10110101.10011110.00000000.00000000181.158.0.0
Broadcast10110101.10011111.11111111.11111111181.159.255.255
Split into smaller subnets/24
/16 (2)/17 (4)/18 (8)/19 (16)/20 (32)/21 (64)/22 (128)/23 (256)/24 (512)/25 (1,024)/26 (2,048)/27 (4,096)

181.158.0.0/15 makes 512 subnets of /24; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1181.158.0.0/24181.158.0.1 to 181.158.0.254181.158.0.255254
2181.158.1.0/24181.158.1.1 to 181.158.1.254181.158.1.255254
3181.158.2.0/24181.158.2.1 to 181.158.2.254181.158.2.255254
4181.158.3.0/24181.158.3.1 to 181.158.3.254181.158.3.255254
5181.158.4.0/24181.158.4.1 to 181.158.4.254181.158.4.255254
6181.158.5.0/24181.158.5.1 to 181.158.5.254181.158.5.255254
7181.158.6.0/24181.158.6.1 to 181.158.6.254181.158.6.255254
8181.158.7.0/24181.158.7.1 to 181.158.7.254181.158.7.255254
9181.158.8.0/24181.158.8.1 to 181.158.8.254181.158.8.255254
10181.158.9.0/24181.158.9.1 to 181.158.9.254181.158.9.255254
11181.158.10.0/24181.158.10.1 to 181.158.10.254181.158.10.255254
12181.158.11.0/24181.158.11.1 to 181.158.11.254181.158.11.255254
13181.158.12.0/24181.158.12.1 to 181.158.12.254181.158.12.255254
14181.158.13.0/24181.158.13.1 to 181.158.13.254181.158.13.255254
15181.158.14.0/24181.158.14.1 to 181.158.14.254181.158.14.255254
16181.158.15.0/24181.158.15.1 to 181.158.15.254181.158.15.255254
17181.158.16.0/24181.158.16.1 to 181.158.16.254181.158.16.255254
18181.158.17.0/24181.158.17.1 to 181.158.17.254181.158.17.255254
19181.158.18.0/24181.158.18.1 to 181.158.18.254181.158.18.255254
20181.158.19.0/24181.158.19.1 to 181.158.19.254181.158.19.255254
21181.158.20.0/24181.158.20.1 to 181.158.20.254181.158.20.255254
22181.158.21.0/24181.158.21.1 to 181.158.21.254181.158.21.255254
23181.158.22.0/24181.158.22.1 to 181.158.22.254181.158.22.255254
24181.158.23.0/24181.158.23.1 to 181.158.23.254181.158.23.255254
25181.158.24.0/24181.158.24.1 to 181.158.24.254181.158.24.255254
26181.158.25.0/24181.158.25.1 to 181.158.25.254181.158.25.255254
27181.158.26.0/24181.158.26.1 to 181.158.26.254181.158.26.255254
28181.158.27.0/24181.158.27.1 to 181.158.27.254181.158.27.255254
29181.158.28.0/24181.158.28.1 to 181.158.28.254181.158.28.255254
30181.158.29.0/24181.158.29.1 to 181.158.29.254181.158.29.255254
31181.158.30.0/24181.158.30.1 to 181.158.30.254181.158.30.255254
32181.158.31.0/24181.158.31.1 to 181.158.31.254181.158.31.255254
33181.158.32.0/24181.158.32.1 to 181.158.32.254181.158.32.255254
34181.158.33.0/24181.158.33.1 to 181.158.33.254181.158.33.255254
35181.158.34.0/24181.158.34.1 to 181.158.34.254181.158.34.255254
36181.158.35.0/24181.158.35.1 to 181.158.35.254181.158.35.255254
37181.158.36.0/24181.158.36.1 to 181.158.36.254181.158.36.255254
38181.158.37.0/24181.158.37.1 to 181.158.37.254181.158.37.255254
39181.158.38.0/24181.158.38.1 to 181.158.38.254181.158.38.255254
40181.158.39.0/24181.158.39.1 to 181.158.39.254181.158.39.255254
41181.158.40.0/24181.158.40.1 to 181.158.40.254181.158.40.255254
42181.158.41.0/24181.158.41.1 to 181.158.41.254181.158.41.255254
43181.158.42.0/24181.158.42.1 to 181.158.42.254181.158.42.255254
44181.158.43.0/24181.158.43.1 to 181.158.43.254181.158.43.255254
45181.158.44.0/24181.158.44.1 to 181.158.44.254181.158.44.255254
46181.158.45.0/24181.158.45.1 to 181.158.45.254181.158.45.255254
47181.158.46.0/24181.158.46.1 to 181.158.46.254181.158.46.255254
48181.158.47.0/24181.158.47.1 to 181.158.47.254181.158.47.255254
49181.158.48.0/24181.158.48.1 to 181.158.48.254181.158.48.255254
50181.158.49.0/24181.158.49.1 to 181.158.49.254181.158.49.255254
51181.158.50.0/24181.158.50.1 to 181.158.50.254181.158.50.255254
52181.158.51.0/24181.158.51.1 to 181.158.51.254181.158.51.255254
53181.158.52.0/24181.158.52.1 to 181.158.52.254181.158.52.255254
54181.158.53.0/24181.158.53.1 to 181.158.53.254181.158.53.255254
55181.158.54.0/24181.158.54.1 to 181.158.54.254181.158.54.255254
56181.158.55.0/24181.158.55.1 to 181.158.55.254181.158.55.255254
57181.158.56.0/24181.158.56.1 to 181.158.56.254181.158.56.255254
58181.158.57.0/24181.158.57.1 to 181.158.57.254181.158.57.255254
59181.158.58.0/24181.158.58.1 to 181.158.58.254181.158.58.255254
60181.158.59.0/24181.158.59.1 to 181.158.59.254181.158.59.255254
61181.158.60.0/24181.158.60.1 to 181.158.60.254181.158.60.255254
62181.158.61.0/24181.158.61.1 to 181.158.61.254181.158.61.255254
63181.158.62.0/24181.158.62.1 to 181.158.62.254181.158.62.255254
64181.158.63.0/24181.158.63.1 to 181.158.63.254181.158.63.255254
65181.158.64.0/24181.158.64.1 to 181.158.64.254181.158.64.255254
66181.158.65.0/24181.158.65.1 to 181.158.65.254181.158.65.255254
67181.158.66.0/24181.158.66.1 to 181.158.66.254181.158.66.255254
68181.158.67.0/24181.158.67.1 to 181.158.67.254181.158.67.255254
69181.158.68.0/24181.158.68.1 to 181.158.68.254181.158.68.255254
70181.158.69.0/24181.158.69.1 to 181.158.69.254181.158.69.255254
71181.158.70.0/24181.158.70.1 to 181.158.70.254181.158.70.255254
72181.158.71.0/24181.158.71.1 to 181.158.71.254181.158.71.255254
73181.158.72.0/24181.158.72.1 to 181.158.72.254181.158.72.255254
74181.158.73.0/24181.158.73.1 to 181.158.73.254181.158.73.255254
75181.158.74.0/24181.158.74.1 to 181.158.74.254181.158.74.255254
76181.158.75.0/24181.158.75.1 to 181.158.75.254181.158.75.255254
77181.158.76.0/24181.158.76.1 to 181.158.76.254181.158.76.255254
78181.158.77.0/24181.158.77.1 to 181.158.77.254181.158.77.255254
79181.158.78.0/24181.158.78.1 to 181.158.78.254181.158.78.255254
80181.158.79.0/24181.158.79.1 to 181.158.79.254181.158.79.255254
81181.158.80.0/24181.158.80.1 to 181.158.80.254181.158.80.255254
82181.158.81.0/24181.158.81.1 to 181.158.81.254181.158.81.255254
83181.158.82.0/24181.158.82.1 to 181.158.82.254181.158.82.255254
84181.158.83.0/24181.158.83.1 to 181.158.83.254181.158.83.255254
85181.158.84.0/24181.158.84.1 to 181.158.84.254181.158.84.255254
86181.158.85.0/24181.158.85.1 to 181.158.85.254181.158.85.255254
87181.158.86.0/24181.158.86.1 to 181.158.86.254181.158.86.255254
88181.158.87.0/24181.158.87.1 to 181.158.87.254181.158.87.255254
89181.158.88.0/24181.158.88.1 to 181.158.88.254181.158.88.255254
90181.158.89.0/24181.158.89.1 to 181.158.89.254181.158.89.255254
91181.158.90.0/24181.158.90.1 to 181.158.90.254181.158.90.255254
92181.158.91.0/24181.158.91.1 to 181.158.91.254181.158.91.255254
93181.158.92.0/24181.158.92.1 to 181.158.92.254181.158.92.255254
94181.158.93.0/24181.158.93.1 to 181.158.93.254181.158.93.255254
95181.158.94.0/24181.158.94.1 to 181.158.94.254181.158.94.255254
96181.158.95.0/24181.158.95.1 to 181.158.95.254181.158.95.255254
97181.158.96.0/24181.158.96.1 to 181.158.96.254181.158.96.255254
98181.158.97.0/24181.158.97.1 to 181.158.97.254181.158.97.255254
99181.158.98.0/24181.158.98.1 to 181.158.98.254181.158.98.255254
100181.158.99.0/24181.158.99.1 to 181.158.99.254181.158.99.255254
101181.158.100.0/24181.158.100.1 to 181.158.100.254181.158.100.255254
102181.158.101.0/24181.158.101.1 to 181.158.101.254181.158.101.255254
103181.158.102.0/24181.158.102.1 to 181.158.102.254181.158.102.255254
104181.158.103.0/24181.158.103.1 to 181.158.103.254181.158.103.255254
105181.158.104.0/24181.158.104.1 to 181.158.104.254181.158.104.255254
106181.158.105.0/24181.158.105.1 to 181.158.105.254181.158.105.255254
107181.158.106.0/24181.158.106.1 to 181.158.106.254181.158.106.255254
108181.158.107.0/24181.158.107.1 to 181.158.107.254181.158.107.255254
109181.158.108.0/24181.158.108.1 to 181.158.108.254181.158.108.255254
110181.158.109.0/24181.158.109.1 to 181.158.109.254181.158.109.255254
111181.158.110.0/24181.158.110.1 to 181.158.110.254181.158.110.255254
112181.158.111.0/24181.158.111.1 to 181.158.111.254181.158.111.255254
113181.158.112.0/24181.158.112.1 to 181.158.112.254181.158.112.255254
114181.158.113.0/24181.158.113.1 to 181.158.113.254181.158.113.255254
115181.158.114.0/24181.158.114.1 to 181.158.114.254181.158.114.255254
116181.158.115.0/24181.158.115.1 to 181.158.115.254181.158.115.255254
117181.158.116.0/24181.158.116.1 to 181.158.116.254181.158.116.255254
118181.158.117.0/24181.158.117.1 to 181.158.117.254181.158.117.255254
119181.158.118.0/24181.158.118.1 to 181.158.118.254181.158.118.255254
120181.158.119.0/24181.158.119.1 to 181.158.119.254181.158.119.255254
121181.158.120.0/24181.158.120.1 to 181.158.120.254181.158.120.255254
122181.158.121.0/24181.158.121.1 to 181.158.121.254181.158.121.255254
123181.158.122.0/24181.158.122.1 to 181.158.122.254181.158.122.255254
124181.158.123.0/24181.158.123.1 to 181.158.123.254181.158.123.255254
125181.158.124.0/24181.158.124.1 to 181.158.124.254181.158.124.255254
126181.158.125.0/24181.158.125.1 to 181.158.125.254181.158.125.255254
127181.158.126.0/24181.158.126.1 to 181.158.126.254181.158.126.255254
128181.158.127.0/24181.158.127.1 to 181.158.127.254181.158.127.255254
129181.158.128.0/24181.158.128.1 to 181.158.128.254181.158.128.255254
130181.158.129.0/24181.158.129.1 to 181.158.129.254181.158.129.255254
131181.158.130.0/24181.158.130.1 to 181.158.130.254181.158.130.255254
132181.158.131.0/24181.158.131.1 to 181.158.131.254181.158.131.255254
133181.158.132.0/24181.158.132.1 to 181.158.132.254181.158.132.255254
134181.158.133.0/24181.158.133.1 to 181.158.133.254181.158.133.255254
135181.158.134.0/24181.158.134.1 to 181.158.134.254181.158.134.255254
136181.158.135.0/24181.158.135.1 to 181.158.135.254181.158.135.255254
137181.158.136.0/24181.158.136.1 to 181.158.136.254181.158.136.255254
138181.158.137.0/24181.158.137.1 to 181.158.137.254181.158.137.255254
139181.158.138.0/24181.158.138.1 to 181.158.138.254181.158.138.255254
140181.158.139.0/24181.158.139.1 to 181.158.139.254181.158.139.255254
141181.158.140.0/24181.158.140.1 to 181.158.140.254181.158.140.255254
142181.158.141.0/24181.158.141.1 to 181.158.141.254181.158.141.255254
143181.158.142.0/24181.158.142.1 to 181.158.142.254181.158.142.255254
144181.158.143.0/24181.158.143.1 to 181.158.143.254181.158.143.255254
145181.158.144.0/24181.158.144.1 to 181.158.144.254181.158.144.255254
146181.158.145.0/24181.158.145.1 to 181.158.145.254181.158.145.255254
147181.158.146.0/24181.158.146.1 to 181.158.146.254181.158.146.255254
148181.158.147.0/24181.158.147.1 to 181.158.147.254181.158.147.255254
149181.158.148.0/24181.158.148.1 to 181.158.148.254181.158.148.255254
150181.158.149.0/24181.158.149.1 to 181.158.149.254181.158.149.255254
151181.158.150.0/24181.158.150.1 to 181.158.150.254181.158.150.255254
152181.158.151.0/24181.158.151.1 to 181.158.151.254181.158.151.255254
153181.158.152.0/24181.158.152.1 to 181.158.152.254181.158.152.255254
154181.158.153.0/24181.158.153.1 to 181.158.153.254181.158.153.255254
155181.158.154.0/24181.158.154.1 to 181.158.154.254181.158.154.255254
156181.158.155.0/24181.158.155.1 to 181.158.155.254181.158.155.255254
157181.158.156.0/24181.158.156.1 to 181.158.156.254181.158.156.255254
158181.158.157.0/24181.158.157.1 to 181.158.157.254181.158.157.255254
159181.158.158.0/24181.158.158.1 to 181.158.158.254181.158.158.255254
160181.158.159.0/24181.158.159.1 to 181.158.159.254181.158.159.255254
161181.158.160.0/24181.158.160.1 to 181.158.160.254181.158.160.255254
162181.158.161.0/24181.158.161.1 to 181.158.161.254181.158.161.255254
163181.158.162.0/24181.158.162.1 to 181.158.162.254181.158.162.255254
164181.158.163.0/24181.158.163.1 to 181.158.163.254181.158.163.255254
165181.158.164.0/24181.158.164.1 to 181.158.164.254181.158.164.255254
166181.158.165.0/24181.158.165.1 to 181.158.165.254181.158.165.255254
167181.158.166.0/24181.158.166.1 to 181.158.166.254181.158.166.255254
168181.158.167.0/24181.158.167.1 to 181.158.167.254181.158.167.255254
169181.158.168.0/24181.158.168.1 to 181.158.168.254181.158.168.255254
170181.158.169.0/24181.158.169.1 to 181.158.169.254181.158.169.255254
171181.158.170.0/24181.158.170.1 to 181.158.170.254181.158.170.255254
172181.158.171.0/24181.158.171.1 to 181.158.171.254181.158.171.255254
173181.158.172.0/24181.158.172.1 to 181.158.172.254181.158.172.255254
174181.158.173.0/24181.158.173.1 to 181.158.173.254181.158.173.255254
175181.158.174.0/24181.158.174.1 to 181.158.174.254181.158.174.255254
176181.158.175.0/24181.158.175.1 to 181.158.175.254181.158.175.255254
177181.158.176.0/24181.158.176.1 to 181.158.176.254181.158.176.255254
178181.158.177.0/24181.158.177.1 to 181.158.177.254181.158.177.255254
179181.158.178.0/24181.158.178.1 to 181.158.178.254181.158.178.255254
180181.158.179.0/24181.158.179.1 to 181.158.179.254181.158.179.255254
181181.158.180.0/24181.158.180.1 to 181.158.180.254181.158.180.255254
182181.158.181.0/24181.158.181.1 to 181.158.181.254181.158.181.255254
183181.158.182.0/24181.158.182.1 to 181.158.182.254181.158.182.255254
184181.158.183.0/24181.158.183.1 to 181.158.183.254181.158.183.255254
185181.158.184.0/24181.158.184.1 to 181.158.184.254181.158.184.255254
186181.158.185.0/24181.158.185.1 to 181.158.185.254181.158.185.255254
187181.158.186.0/24181.158.186.1 to 181.158.186.254181.158.186.255254
188181.158.187.0/24181.158.187.1 to 181.158.187.254181.158.187.255254
189181.158.188.0/24181.158.188.1 to 181.158.188.254181.158.188.255254
190181.158.189.0/24181.158.189.1 to 181.158.189.254181.158.189.255254
191181.158.190.0/24181.158.190.1 to 181.158.190.254181.158.190.255254
192181.158.191.0/24181.158.191.1 to 181.158.191.254181.158.191.255254
193181.158.192.0/24181.158.192.1 to 181.158.192.254181.158.192.255254
194181.158.193.0/24181.158.193.1 to 181.158.193.254181.158.193.255254
195181.158.194.0/24181.158.194.1 to 181.158.194.254181.158.194.255254
196181.158.195.0/24181.158.195.1 to 181.158.195.254181.158.195.255254
197181.158.196.0/24181.158.196.1 to 181.158.196.254181.158.196.255254
198181.158.197.0/24181.158.197.1 to 181.158.197.254181.158.197.255254
199181.158.198.0/24181.158.198.1 to 181.158.198.254181.158.198.255254
200181.158.199.0/24181.158.199.1 to 181.158.199.254181.158.199.255254
201181.158.200.0/24181.158.200.1 to 181.158.200.254181.158.200.255254
202181.158.201.0/24181.158.201.1 to 181.158.201.254181.158.201.255254
203181.158.202.0/24181.158.202.1 to 181.158.202.254181.158.202.255254
204181.158.203.0/24181.158.203.1 to 181.158.203.254181.158.203.255254
205181.158.204.0/24181.158.204.1 to 181.158.204.254181.158.204.255254
206181.158.205.0/24181.158.205.1 to 181.158.205.254181.158.205.255254
207181.158.206.0/24181.158.206.1 to 181.158.206.254181.158.206.255254
208181.158.207.0/24181.158.207.1 to 181.158.207.254181.158.207.255254
209181.158.208.0/24181.158.208.1 to 181.158.208.254181.158.208.255254
210181.158.209.0/24181.158.209.1 to 181.158.209.254181.158.209.255254
211181.158.210.0/24181.158.210.1 to 181.158.210.254181.158.210.255254
212181.158.211.0/24181.158.211.1 to 181.158.211.254181.158.211.255254
213181.158.212.0/24181.158.212.1 to 181.158.212.254181.158.212.255254
214181.158.213.0/24181.158.213.1 to 181.158.213.254181.158.213.255254
215181.158.214.0/24181.158.214.1 to 181.158.214.254181.158.214.255254
216181.158.215.0/24181.158.215.1 to 181.158.215.254181.158.215.255254
217181.158.216.0/24181.158.216.1 to 181.158.216.254181.158.216.255254
218181.158.217.0/24181.158.217.1 to 181.158.217.254181.158.217.255254
219181.158.218.0/24181.158.218.1 to 181.158.218.254181.158.218.255254
220181.158.219.0/24181.158.219.1 to 181.158.219.254181.158.219.255254
221181.158.220.0/24181.158.220.1 to 181.158.220.254181.158.220.255254
222181.158.221.0/24181.158.221.1 to 181.158.221.254181.158.221.255254
223181.158.222.0/24181.158.222.1 to 181.158.222.254181.158.222.255254
224181.158.223.0/24181.158.223.1 to 181.158.223.254181.158.223.255254
225181.158.224.0/24181.158.224.1 to 181.158.224.254181.158.224.255254
226181.158.225.0/24181.158.225.1 to 181.158.225.254181.158.225.255254
227181.158.226.0/24181.158.226.1 to 181.158.226.254181.158.226.255254
228181.158.227.0/24181.158.227.1 to 181.158.227.254181.158.227.255254
229181.158.228.0/24181.158.228.1 to 181.158.228.254181.158.228.255254
230181.158.229.0/24181.158.229.1 to 181.158.229.254181.158.229.255254
231181.158.230.0/24181.158.230.1 to 181.158.230.254181.158.230.255254
232181.158.231.0/24181.158.231.1 to 181.158.231.254181.158.231.255254
233181.158.232.0/24181.158.232.1 to 181.158.232.254181.158.232.255254
234181.158.233.0/24181.158.233.1 to 181.158.233.254181.158.233.255254
235181.158.234.0/24181.158.234.1 to 181.158.234.254181.158.234.255254
236181.158.235.0/24181.158.235.1 to 181.158.235.254181.158.235.255254
237181.158.236.0/24181.158.236.1 to 181.158.236.254181.158.236.255254
238181.158.237.0/24181.158.237.1 to 181.158.237.254181.158.237.255254
239181.158.238.0/24181.158.238.1 to 181.158.238.254181.158.238.255254
240181.158.239.0/24181.158.239.1 to 181.158.239.254181.158.239.255254
241181.158.240.0/24181.158.240.1 to 181.158.240.254181.158.240.255254
242181.158.241.0/24181.158.241.1 to 181.158.241.254181.158.241.255254
243181.158.242.0/24181.158.242.1 to 181.158.242.254181.158.242.255254
244181.158.243.0/24181.158.243.1 to 181.158.243.254181.158.243.255254
245181.158.244.0/24181.158.244.1 to 181.158.244.254181.158.244.255254
246181.158.245.0/24181.158.245.1 to 181.158.245.254181.158.245.255254
247181.158.246.0/24181.158.246.1 to 181.158.246.254181.158.246.255254
248181.158.247.0/24181.158.247.1 to 181.158.247.254181.158.247.255254
249181.158.248.0/24181.158.248.1 to 181.158.248.254181.158.248.255254
250181.158.249.0/24181.158.249.1 to 181.158.249.254181.158.249.255254
251181.158.250.0/24181.158.250.1 to 181.158.250.254181.158.250.255254
252181.158.251.0/24181.158.251.1 to 181.158.251.254181.158.251.255254
253181.158.252.0/24181.158.252.1 to 181.158.252.254181.158.252.255254
254181.158.253.0/24181.158.253.1 to 181.158.253.254181.158.253.255254
255181.158.254.0/24181.158.254.1 to 181.158.254.254181.158.254.255254
256181.158.255.0/24181.158.255.1 to 181.158.255.254181.158.255.255254

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.