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.

Network232.112.0.0/12
Usable hosts1,048,574
Subnet mask255.240.0.0
Addresses1,048,576
Network address
232.112.0.0
Broadcast address
232.127.255.255
First usable
232.112.0.1
Last usable
232.127.255.254
Usable hosts
1,048,574 (1,048,576 less the network and broadcast addresses)
Subnet mask
255.240.0.0
Wildcard mask
0.15.255.255 (Cisco ACLs, OSPF)
Prefix length
/12
Type
Multicast 224.0.0.0/4
One-to-many traffic, such as IPTV and routing protocols
Old class
D (multicast)
As numbers
Hex E8700000 · Integer 3899654144 to 3900702719
Reverse DNS zones
112.232.in-addr.arpa
113.232.in-addr.arpa
114.232.in-addr.arpa
115.232.in-addr.arpa
116.232.in-addr.arpa
117.232.in-addr.arpa
118.232.in-addr.arpa
119.232.in-addr.arpa
120.232.in-addr.arpa
121.232.in-addr.arpa
122.232.in-addr.arpa
123.232.in-addr.arpa
124.232.in-addr.arpa
125.232.in-addr.arpa
126.232.in-addr.arpa
127.232.in-addr.arpa
/12 is not on a 8-bit boundary, so it takes 16 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11101000.01110000.00000000.00000000232.112.0.0
Subnet mask11111111.11110000.00000000.00000000255.240.0.0
Network11101000.01110000.00000000.00000000232.112.0.0
Broadcast11101000.01111111.11111111.11111111232.127.255.255
Split into smaller subnets/23
/13 (2)/14 (4)/15 (8)/16 (16)/17 (32)/18 (64)/19 (128)/20 (256)/21 (512)/22 (1,024)/23 (2,048)/24 (4,096)

232.112.0.0/12 makes 2,048 subnets of /23; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1232.112.0.0/23232.112.0.1 to 232.112.1.254232.112.1.255510
2232.112.2.0/23232.112.2.1 to 232.112.3.254232.112.3.255510
3232.112.4.0/23232.112.4.1 to 232.112.5.254232.112.5.255510
4232.112.6.0/23232.112.6.1 to 232.112.7.254232.112.7.255510
5232.112.8.0/23232.112.8.1 to 232.112.9.254232.112.9.255510
6232.112.10.0/23232.112.10.1 to 232.112.11.254232.112.11.255510
7232.112.12.0/23232.112.12.1 to 232.112.13.254232.112.13.255510
8232.112.14.0/23232.112.14.1 to 232.112.15.254232.112.15.255510
9232.112.16.0/23232.112.16.1 to 232.112.17.254232.112.17.255510
10232.112.18.0/23232.112.18.1 to 232.112.19.254232.112.19.255510
11232.112.20.0/23232.112.20.1 to 232.112.21.254232.112.21.255510
12232.112.22.0/23232.112.22.1 to 232.112.23.254232.112.23.255510
13232.112.24.0/23232.112.24.1 to 232.112.25.254232.112.25.255510
14232.112.26.0/23232.112.26.1 to 232.112.27.254232.112.27.255510
15232.112.28.0/23232.112.28.1 to 232.112.29.254232.112.29.255510
16232.112.30.0/23232.112.30.1 to 232.112.31.254232.112.31.255510
17232.112.32.0/23232.112.32.1 to 232.112.33.254232.112.33.255510
18232.112.34.0/23232.112.34.1 to 232.112.35.254232.112.35.255510
19232.112.36.0/23232.112.36.1 to 232.112.37.254232.112.37.255510
20232.112.38.0/23232.112.38.1 to 232.112.39.254232.112.39.255510
21232.112.40.0/23232.112.40.1 to 232.112.41.254232.112.41.255510
22232.112.42.0/23232.112.42.1 to 232.112.43.254232.112.43.255510
23232.112.44.0/23232.112.44.1 to 232.112.45.254232.112.45.255510
24232.112.46.0/23232.112.46.1 to 232.112.47.254232.112.47.255510
25232.112.48.0/23232.112.48.1 to 232.112.49.254232.112.49.255510
26232.112.50.0/23232.112.50.1 to 232.112.51.254232.112.51.255510
27232.112.52.0/23232.112.52.1 to 232.112.53.254232.112.53.255510
28232.112.54.0/23232.112.54.1 to 232.112.55.254232.112.55.255510
29232.112.56.0/23232.112.56.1 to 232.112.57.254232.112.57.255510
30232.112.58.0/23232.112.58.1 to 232.112.59.254232.112.59.255510
31232.112.60.0/23232.112.60.1 to 232.112.61.254232.112.61.255510
32232.112.62.0/23232.112.62.1 to 232.112.63.254232.112.63.255510
33232.112.64.0/23232.112.64.1 to 232.112.65.254232.112.65.255510
34232.112.66.0/23232.112.66.1 to 232.112.67.254232.112.67.255510
35232.112.68.0/23232.112.68.1 to 232.112.69.254232.112.69.255510
36232.112.70.0/23232.112.70.1 to 232.112.71.254232.112.71.255510
37232.112.72.0/23232.112.72.1 to 232.112.73.254232.112.73.255510
38232.112.74.0/23232.112.74.1 to 232.112.75.254232.112.75.255510
39232.112.76.0/23232.112.76.1 to 232.112.77.254232.112.77.255510
40232.112.78.0/23232.112.78.1 to 232.112.79.254232.112.79.255510
41232.112.80.0/23232.112.80.1 to 232.112.81.254232.112.81.255510
42232.112.82.0/23232.112.82.1 to 232.112.83.254232.112.83.255510
43232.112.84.0/23232.112.84.1 to 232.112.85.254232.112.85.255510
44232.112.86.0/23232.112.86.1 to 232.112.87.254232.112.87.255510
45232.112.88.0/23232.112.88.1 to 232.112.89.254232.112.89.255510
46232.112.90.0/23232.112.90.1 to 232.112.91.254232.112.91.255510
47232.112.92.0/23232.112.92.1 to 232.112.93.254232.112.93.255510
48232.112.94.0/23232.112.94.1 to 232.112.95.254232.112.95.255510
49232.112.96.0/23232.112.96.1 to 232.112.97.254232.112.97.255510
50232.112.98.0/23232.112.98.1 to 232.112.99.254232.112.99.255510
51232.112.100.0/23232.112.100.1 to 232.112.101.254232.112.101.255510
52232.112.102.0/23232.112.102.1 to 232.112.103.254232.112.103.255510
53232.112.104.0/23232.112.104.1 to 232.112.105.254232.112.105.255510
54232.112.106.0/23232.112.106.1 to 232.112.107.254232.112.107.255510
55232.112.108.0/23232.112.108.1 to 232.112.109.254232.112.109.255510
56232.112.110.0/23232.112.110.1 to 232.112.111.254232.112.111.255510
57232.112.112.0/23232.112.112.1 to 232.112.113.254232.112.113.255510
58232.112.114.0/23232.112.114.1 to 232.112.115.254232.112.115.255510
59232.112.116.0/23232.112.116.1 to 232.112.117.254232.112.117.255510
60232.112.118.0/23232.112.118.1 to 232.112.119.254232.112.119.255510
61232.112.120.0/23232.112.120.1 to 232.112.121.254232.112.121.255510
62232.112.122.0/23232.112.122.1 to 232.112.123.254232.112.123.255510
63232.112.124.0/23232.112.124.1 to 232.112.125.254232.112.125.255510
64232.112.126.0/23232.112.126.1 to 232.112.127.254232.112.127.255510
65232.112.128.0/23232.112.128.1 to 232.112.129.254232.112.129.255510
66232.112.130.0/23232.112.130.1 to 232.112.131.254232.112.131.255510
67232.112.132.0/23232.112.132.1 to 232.112.133.254232.112.133.255510
68232.112.134.0/23232.112.134.1 to 232.112.135.254232.112.135.255510
69232.112.136.0/23232.112.136.1 to 232.112.137.254232.112.137.255510
70232.112.138.0/23232.112.138.1 to 232.112.139.254232.112.139.255510
71232.112.140.0/23232.112.140.1 to 232.112.141.254232.112.141.255510
72232.112.142.0/23232.112.142.1 to 232.112.143.254232.112.143.255510
73232.112.144.0/23232.112.144.1 to 232.112.145.254232.112.145.255510
74232.112.146.0/23232.112.146.1 to 232.112.147.254232.112.147.255510
75232.112.148.0/23232.112.148.1 to 232.112.149.254232.112.149.255510
76232.112.150.0/23232.112.150.1 to 232.112.151.254232.112.151.255510
77232.112.152.0/23232.112.152.1 to 232.112.153.254232.112.153.255510
78232.112.154.0/23232.112.154.1 to 232.112.155.254232.112.155.255510
79232.112.156.0/23232.112.156.1 to 232.112.157.254232.112.157.255510
80232.112.158.0/23232.112.158.1 to 232.112.159.254232.112.159.255510
81232.112.160.0/23232.112.160.1 to 232.112.161.254232.112.161.255510
82232.112.162.0/23232.112.162.1 to 232.112.163.254232.112.163.255510
83232.112.164.0/23232.112.164.1 to 232.112.165.254232.112.165.255510
84232.112.166.0/23232.112.166.1 to 232.112.167.254232.112.167.255510
85232.112.168.0/23232.112.168.1 to 232.112.169.254232.112.169.255510
86232.112.170.0/23232.112.170.1 to 232.112.171.254232.112.171.255510
87232.112.172.0/23232.112.172.1 to 232.112.173.254232.112.173.255510
88232.112.174.0/23232.112.174.1 to 232.112.175.254232.112.175.255510
89232.112.176.0/23232.112.176.1 to 232.112.177.254232.112.177.255510
90232.112.178.0/23232.112.178.1 to 232.112.179.254232.112.179.255510
91232.112.180.0/23232.112.180.1 to 232.112.181.254232.112.181.255510
92232.112.182.0/23232.112.182.1 to 232.112.183.254232.112.183.255510
93232.112.184.0/23232.112.184.1 to 232.112.185.254232.112.185.255510
94232.112.186.0/23232.112.186.1 to 232.112.187.254232.112.187.255510
95232.112.188.0/23232.112.188.1 to 232.112.189.254232.112.189.255510
96232.112.190.0/23232.112.190.1 to 232.112.191.254232.112.191.255510
97232.112.192.0/23232.112.192.1 to 232.112.193.254232.112.193.255510
98232.112.194.0/23232.112.194.1 to 232.112.195.254232.112.195.255510
99232.112.196.0/23232.112.196.1 to 232.112.197.254232.112.197.255510
100232.112.198.0/23232.112.198.1 to 232.112.199.254232.112.199.255510
101232.112.200.0/23232.112.200.1 to 232.112.201.254232.112.201.255510
102232.112.202.0/23232.112.202.1 to 232.112.203.254232.112.203.255510
103232.112.204.0/23232.112.204.1 to 232.112.205.254232.112.205.255510
104232.112.206.0/23232.112.206.1 to 232.112.207.254232.112.207.255510
105232.112.208.0/23232.112.208.1 to 232.112.209.254232.112.209.255510
106232.112.210.0/23232.112.210.1 to 232.112.211.254232.112.211.255510
107232.112.212.0/23232.112.212.1 to 232.112.213.254232.112.213.255510
108232.112.214.0/23232.112.214.1 to 232.112.215.254232.112.215.255510
109232.112.216.0/23232.112.216.1 to 232.112.217.254232.112.217.255510
110232.112.218.0/23232.112.218.1 to 232.112.219.254232.112.219.255510
111232.112.220.0/23232.112.220.1 to 232.112.221.254232.112.221.255510
112232.112.222.0/23232.112.222.1 to 232.112.223.254232.112.223.255510
113232.112.224.0/23232.112.224.1 to 232.112.225.254232.112.225.255510
114232.112.226.0/23232.112.226.1 to 232.112.227.254232.112.227.255510
115232.112.228.0/23232.112.228.1 to 232.112.229.254232.112.229.255510
116232.112.230.0/23232.112.230.1 to 232.112.231.254232.112.231.255510
117232.112.232.0/23232.112.232.1 to 232.112.233.254232.112.233.255510
118232.112.234.0/23232.112.234.1 to 232.112.235.254232.112.235.255510
119232.112.236.0/23232.112.236.1 to 232.112.237.254232.112.237.255510
120232.112.238.0/23232.112.238.1 to 232.112.239.254232.112.239.255510
121232.112.240.0/23232.112.240.1 to 232.112.241.254232.112.241.255510
122232.112.242.0/23232.112.242.1 to 232.112.243.254232.112.243.255510
123232.112.244.0/23232.112.244.1 to 232.112.245.254232.112.245.255510
124232.112.246.0/23232.112.246.1 to 232.112.247.254232.112.247.255510
125232.112.248.0/23232.112.248.1 to 232.112.249.254232.112.249.255510
126232.112.250.0/23232.112.250.1 to 232.112.251.254232.112.251.255510
127232.112.252.0/23232.112.252.1 to 232.112.253.254232.112.253.255510
128232.112.254.0/23232.112.254.1 to 232.112.255.254232.112.255.255510
129232.113.0.0/23232.113.0.1 to 232.113.1.254232.113.1.255510
130232.113.2.0/23232.113.2.1 to 232.113.3.254232.113.3.255510
131232.113.4.0/23232.113.4.1 to 232.113.5.254232.113.5.255510
132232.113.6.0/23232.113.6.1 to 232.113.7.254232.113.7.255510
133232.113.8.0/23232.113.8.1 to 232.113.9.254232.113.9.255510
134232.113.10.0/23232.113.10.1 to 232.113.11.254232.113.11.255510
135232.113.12.0/23232.113.12.1 to 232.113.13.254232.113.13.255510
136232.113.14.0/23232.113.14.1 to 232.113.15.254232.113.15.255510
137232.113.16.0/23232.113.16.1 to 232.113.17.254232.113.17.255510
138232.113.18.0/23232.113.18.1 to 232.113.19.254232.113.19.255510
139232.113.20.0/23232.113.20.1 to 232.113.21.254232.113.21.255510
140232.113.22.0/23232.113.22.1 to 232.113.23.254232.113.23.255510
141232.113.24.0/23232.113.24.1 to 232.113.25.254232.113.25.255510
142232.113.26.0/23232.113.26.1 to 232.113.27.254232.113.27.255510
143232.113.28.0/23232.113.28.1 to 232.113.29.254232.113.29.255510
144232.113.30.0/23232.113.30.1 to 232.113.31.254232.113.31.255510
145232.113.32.0/23232.113.32.1 to 232.113.33.254232.113.33.255510
146232.113.34.0/23232.113.34.1 to 232.113.35.254232.113.35.255510
147232.113.36.0/23232.113.36.1 to 232.113.37.254232.113.37.255510
148232.113.38.0/23232.113.38.1 to 232.113.39.254232.113.39.255510
149232.113.40.0/23232.113.40.1 to 232.113.41.254232.113.41.255510
150232.113.42.0/23232.113.42.1 to 232.113.43.254232.113.43.255510
151232.113.44.0/23232.113.44.1 to 232.113.45.254232.113.45.255510
152232.113.46.0/23232.113.46.1 to 232.113.47.254232.113.47.255510
153232.113.48.0/23232.113.48.1 to 232.113.49.254232.113.49.255510
154232.113.50.0/23232.113.50.1 to 232.113.51.254232.113.51.255510
155232.113.52.0/23232.113.52.1 to 232.113.53.254232.113.53.255510
156232.113.54.0/23232.113.54.1 to 232.113.55.254232.113.55.255510
157232.113.56.0/23232.113.56.1 to 232.113.57.254232.113.57.255510
158232.113.58.0/23232.113.58.1 to 232.113.59.254232.113.59.255510
159232.113.60.0/23232.113.60.1 to 232.113.61.254232.113.61.255510
160232.113.62.0/23232.113.62.1 to 232.113.63.254232.113.63.255510
161232.113.64.0/23232.113.64.1 to 232.113.65.254232.113.65.255510
162232.113.66.0/23232.113.66.1 to 232.113.67.254232.113.67.255510
163232.113.68.0/23232.113.68.1 to 232.113.69.254232.113.69.255510
164232.113.70.0/23232.113.70.1 to 232.113.71.254232.113.71.255510
165232.113.72.0/23232.113.72.1 to 232.113.73.254232.113.73.255510
166232.113.74.0/23232.113.74.1 to 232.113.75.254232.113.75.255510
167232.113.76.0/23232.113.76.1 to 232.113.77.254232.113.77.255510
168232.113.78.0/23232.113.78.1 to 232.113.79.254232.113.79.255510
169232.113.80.0/23232.113.80.1 to 232.113.81.254232.113.81.255510
170232.113.82.0/23232.113.82.1 to 232.113.83.254232.113.83.255510
171232.113.84.0/23232.113.84.1 to 232.113.85.254232.113.85.255510
172232.113.86.0/23232.113.86.1 to 232.113.87.254232.113.87.255510
173232.113.88.0/23232.113.88.1 to 232.113.89.254232.113.89.255510
174232.113.90.0/23232.113.90.1 to 232.113.91.254232.113.91.255510
175232.113.92.0/23232.113.92.1 to 232.113.93.254232.113.93.255510
176232.113.94.0/23232.113.94.1 to 232.113.95.254232.113.95.255510
177232.113.96.0/23232.113.96.1 to 232.113.97.254232.113.97.255510
178232.113.98.0/23232.113.98.1 to 232.113.99.254232.113.99.255510
179232.113.100.0/23232.113.100.1 to 232.113.101.254232.113.101.255510
180232.113.102.0/23232.113.102.1 to 232.113.103.254232.113.103.255510
181232.113.104.0/23232.113.104.1 to 232.113.105.254232.113.105.255510
182232.113.106.0/23232.113.106.1 to 232.113.107.254232.113.107.255510
183232.113.108.0/23232.113.108.1 to 232.113.109.254232.113.109.255510
184232.113.110.0/23232.113.110.1 to 232.113.111.254232.113.111.255510
185232.113.112.0/23232.113.112.1 to 232.113.113.254232.113.113.255510
186232.113.114.0/23232.113.114.1 to 232.113.115.254232.113.115.255510
187232.113.116.0/23232.113.116.1 to 232.113.117.254232.113.117.255510
188232.113.118.0/23232.113.118.1 to 232.113.119.254232.113.119.255510
189232.113.120.0/23232.113.120.1 to 232.113.121.254232.113.121.255510
190232.113.122.0/23232.113.122.1 to 232.113.123.254232.113.123.255510
191232.113.124.0/23232.113.124.1 to 232.113.125.254232.113.125.255510
192232.113.126.0/23232.113.126.1 to 232.113.127.254232.113.127.255510
193232.113.128.0/23232.113.128.1 to 232.113.129.254232.113.129.255510
194232.113.130.0/23232.113.130.1 to 232.113.131.254232.113.131.255510
195232.113.132.0/23232.113.132.1 to 232.113.133.254232.113.133.255510
196232.113.134.0/23232.113.134.1 to 232.113.135.254232.113.135.255510
197232.113.136.0/23232.113.136.1 to 232.113.137.254232.113.137.255510
198232.113.138.0/23232.113.138.1 to 232.113.139.254232.113.139.255510
199232.113.140.0/23232.113.140.1 to 232.113.141.254232.113.141.255510
200232.113.142.0/23232.113.142.1 to 232.113.143.254232.113.143.255510
201232.113.144.0/23232.113.144.1 to 232.113.145.254232.113.145.255510
202232.113.146.0/23232.113.146.1 to 232.113.147.254232.113.147.255510
203232.113.148.0/23232.113.148.1 to 232.113.149.254232.113.149.255510
204232.113.150.0/23232.113.150.1 to 232.113.151.254232.113.151.255510
205232.113.152.0/23232.113.152.1 to 232.113.153.254232.113.153.255510
206232.113.154.0/23232.113.154.1 to 232.113.155.254232.113.155.255510
207232.113.156.0/23232.113.156.1 to 232.113.157.254232.113.157.255510
208232.113.158.0/23232.113.158.1 to 232.113.159.254232.113.159.255510
209232.113.160.0/23232.113.160.1 to 232.113.161.254232.113.161.255510
210232.113.162.0/23232.113.162.1 to 232.113.163.254232.113.163.255510
211232.113.164.0/23232.113.164.1 to 232.113.165.254232.113.165.255510
212232.113.166.0/23232.113.166.1 to 232.113.167.254232.113.167.255510
213232.113.168.0/23232.113.168.1 to 232.113.169.254232.113.169.255510
214232.113.170.0/23232.113.170.1 to 232.113.171.254232.113.171.255510
215232.113.172.0/23232.113.172.1 to 232.113.173.254232.113.173.255510
216232.113.174.0/23232.113.174.1 to 232.113.175.254232.113.175.255510
217232.113.176.0/23232.113.176.1 to 232.113.177.254232.113.177.255510
218232.113.178.0/23232.113.178.1 to 232.113.179.254232.113.179.255510
219232.113.180.0/23232.113.180.1 to 232.113.181.254232.113.181.255510
220232.113.182.0/23232.113.182.1 to 232.113.183.254232.113.183.255510
221232.113.184.0/23232.113.184.1 to 232.113.185.254232.113.185.255510
222232.113.186.0/23232.113.186.1 to 232.113.187.254232.113.187.255510
223232.113.188.0/23232.113.188.1 to 232.113.189.254232.113.189.255510
224232.113.190.0/23232.113.190.1 to 232.113.191.254232.113.191.255510
225232.113.192.0/23232.113.192.1 to 232.113.193.254232.113.193.255510
226232.113.194.0/23232.113.194.1 to 232.113.195.254232.113.195.255510
227232.113.196.0/23232.113.196.1 to 232.113.197.254232.113.197.255510
228232.113.198.0/23232.113.198.1 to 232.113.199.254232.113.199.255510
229232.113.200.0/23232.113.200.1 to 232.113.201.254232.113.201.255510
230232.113.202.0/23232.113.202.1 to 232.113.203.254232.113.203.255510
231232.113.204.0/23232.113.204.1 to 232.113.205.254232.113.205.255510
232232.113.206.0/23232.113.206.1 to 232.113.207.254232.113.207.255510
233232.113.208.0/23232.113.208.1 to 232.113.209.254232.113.209.255510
234232.113.210.0/23232.113.210.1 to 232.113.211.254232.113.211.255510
235232.113.212.0/23232.113.212.1 to 232.113.213.254232.113.213.255510
236232.113.214.0/23232.113.214.1 to 232.113.215.254232.113.215.255510
237232.113.216.0/23232.113.216.1 to 232.113.217.254232.113.217.255510
238232.113.218.0/23232.113.218.1 to 232.113.219.254232.113.219.255510
239232.113.220.0/23232.113.220.1 to 232.113.221.254232.113.221.255510
240232.113.222.0/23232.113.222.1 to 232.113.223.254232.113.223.255510
241232.113.224.0/23232.113.224.1 to 232.113.225.254232.113.225.255510
242232.113.226.0/23232.113.226.1 to 232.113.227.254232.113.227.255510
243232.113.228.0/23232.113.228.1 to 232.113.229.254232.113.229.255510
244232.113.230.0/23232.113.230.1 to 232.113.231.254232.113.231.255510
245232.113.232.0/23232.113.232.1 to 232.113.233.254232.113.233.255510
246232.113.234.0/23232.113.234.1 to 232.113.235.254232.113.235.255510
247232.113.236.0/23232.113.236.1 to 232.113.237.254232.113.237.255510
248232.113.238.0/23232.113.238.1 to 232.113.239.254232.113.239.255510
249232.113.240.0/23232.113.240.1 to 232.113.241.254232.113.241.255510
250232.113.242.0/23232.113.242.1 to 232.113.243.254232.113.243.255510
251232.113.244.0/23232.113.244.1 to 232.113.245.254232.113.245.255510
252232.113.246.0/23232.113.246.1 to 232.113.247.254232.113.247.255510
253232.113.248.0/23232.113.248.1 to 232.113.249.254232.113.249.255510
254232.113.250.0/23232.113.250.1 to 232.113.251.254232.113.251.255510
255232.113.252.0/23232.113.252.1 to 232.113.253.254232.113.253.255510
256232.113.254.0/23232.113.254.1 to 232.113.255.254232.113.255.255510

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.