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.

Network231.26.0.0/19
Usable hosts8,190
Subnet mask255.255.224.0
Addresses8,192
Network address
231.26.0.0
Broadcast address
231.26.31.255
First usable
231.26.0.1
Last usable
231.26.31.254
Usable hosts
8,190 (8,192 less the network and broadcast addresses)
Subnet mask
255.255.224.0
Wildcard mask
0.0.31.255 (Cisco ACLs, OSPF)
Prefix length
/19
Type
Multicast 224.0.0.0/4
One-to-many traffic, such as IPTV and routing protocols
Old class
D (multicast)
As numbers
Hex E71A0000 · Integer 3877240832 to 3877249023
Reverse DNS zones
0.26.231.in-addr.arpa
1.26.231.in-addr.arpa
2.26.231.in-addr.arpa
3.26.231.in-addr.arpa
4.26.231.in-addr.arpa
5.26.231.in-addr.arpa
6.26.231.in-addr.arpa
7.26.231.in-addr.arpa
8.26.231.in-addr.arpa
9.26.231.in-addr.arpa
10.26.231.in-addr.arpa
11.26.231.in-addr.arpa
12.26.231.in-addr.arpa
13.26.231.in-addr.arpa
14.26.231.in-addr.arpa
15.26.231.in-addr.arpa
and 16 more
/19 is not on a 8-bit boundary, so it takes 32 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11100111.00011010.00000000.00000000231.26.0.0
Subnet mask11111111.11111111.11100000.00000000255.255.224.0
Network11100111.00011010.00000000.00000000231.26.0.0
Broadcast11100111.00011010.00011111.11111111231.26.31.255
Split into smaller subnets/27
/20 (2)/21 (4)/22 (8)/23 (16)/24 (32)/25 (64)/26 (128)/27 (256)/28 (512)/29 (1,024)/30 (2,048)/31 (4,096)

231.26.0.0/19 makes 256 subnets of /27.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1231.26.0.0/27231.26.0.1 to 231.26.0.30231.26.0.3130
2231.26.0.32/27231.26.0.33 to 231.26.0.62231.26.0.6330
3231.26.0.64/27231.26.0.65 to 231.26.0.94231.26.0.9530
4231.26.0.96/27231.26.0.97 to 231.26.0.126231.26.0.12730
5231.26.0.128/27231.26.0.129 to 231.26.0.158231.26.0.15930
6231.26.0.160/27231.26.0.161 to 231.26.0.190231.26.0.19130
7231.26.0.192/27231.26.0.193 to 231.26.0.222231.26.0.22330
8231.26.0.224/27231.26.0.225 to 231.26.0.254231.26.0.25530
9231.26.1.0/27231.26.1.1 to 231.26.1.30231.26.1.3130
10231.26.1.32/27231.26.1.33 to 231.26.1.62231.26.1.6330
11231.26.1.64/27231.26.1.65 to 231.26.1.94231.26.1.9530
12231.26.1.96/27231.26.1.97 to 231.26.1.126231.26.1.12730
13231.26.1.128/27231.26.1.129 to 231.26.1.158231.26.1.15930
14231.26.1.160/27231.26.1.161 to 231.26.1.190231.26.1.19130
15231.26.1.192/27231.26.1.193 to 231.26.1.222231.26.1.22330
16231.26.1.224/27231.26.1.225 to 231.26.1.254231.26.1.25530
17231.26.2.0/27231.26.2.1 to 231.26.2.30231.26.2.3130
18231.26.2.32/27231.26.2.33 to 231.26.2.62231.26.2.6330
19231.26.2.64/27231.26.2.65 to 231.26.2.94231.26.2.9530
20231.26.2.96/27231.26.2.97 to 231.26.2.126231.26.2.12730
21231.26.2.128/27231.26.2.129 to 231.26.2.158231.26.2.15930
22231.26.2.160/27231.26.2.161 to 231.26.2.190231.26.2.19130
23231.26.2.192/27231.26.2.193 to 231.26.2.222231.26.2.22330
24231.26.2.224/27231.26.2.225 to 231.26.2.254231.26.2.25530
25231.26.3.0/27231.26.3.1 to 231.26.3.30231.26.3.3130
26231.26.3.32/27231.26.3.33 to 231.26.3.62231.26.3.6330
27231.26.3.64/27231.26.3.65 to 231.26.3.94231.26.3.9530
28231.26.3.96/27231.26.3.97 to 231.26.3.126231.26.3.12730
29231.26.3.128/27231.26.3.129 to 231.26.3.158231.26.3.15930
30231.26.3.160/27231.26.3.161 to 231.26.3.190231.26.3.19130
31231.26.3.192/27231.26.3.193 to 231.26.3.222231.26.3.22330
32231.26.3.224/27231.26.3.225 to 231.26.3.254231.26.3.25530
33231.26.4.0/27231.26.4.1 to 231.26.4.30231.26.4.3130
34231.26.4.32/27231.26.4.33 to 231.26.4.62231.26.4.6330
35231.26.4.64/27231.26.4.65 to 231.26.4.94231.26.4.9530
36231.26.4.96/27231.26.4.97 to 231.26.4.126231.26.4.12730
37231.26.4.128/27231.26.4.129 to 231.26.4.158231.26.4.15930
38231.26.4.160/27231.26.4.161 to 231.26.4.190231.26.4.19130
39231.26.4.192/27231.26.4.193 to 231.26.4.222231.26.4.22330
40231.26.4.224/27231.26.4.225 to 231.26.4.254231.26.4.25530
41231.26.5.0/27231.26.5.1 to 231.26.5.30231.26.5.3130
42231.26.5.32/27231.26.5.33 to 231.26.5.62231.26.5.6330
43231.26.5.64/27231.26.5.65 to 231.26.5.94231.26.5.9530
44231.26.5.96/27231.26.5.97 to 231.26.5.126231.26.5.12730
45231.26.5.128/27231.26.5.129 to 231.26.5.158231.26.5.15930
46231.26.5.160/27231.26.5.161 to 231.26.5.190231.26.5.19130
47231.26.5.192/27231.26.5.193 to 231.26.5.222231.26.5.22330
48231.26.5.224/27231.26.5.225 to 231.26.5.254231.26.5.25530
49231.26.6.0/27231.26.6.1 to 231.26.6.30231.26.6.3130
50231.26.6.32/27231.26.6.33 to 231.26.6.62231.26.6.6330
51231.26.6.64/27231.26.6.65 to 231.26.6.94231.26.6.9530
52231.26.6.96/27231.26.6.97 to 231.26.6.126231.26.6.12730
53231.26.6.128/27231.26.6.129 to 231.26.6.158231.26.6.15930
54231.26.6.160/27231.26.6.161 to 231.26.6.190231.26.6.19130
55231.26.6.192/27231.26.6.193 to 231.26.6.222231.26.6.22330
56231.26.6.224/27231.26.6.225 to 231.26.6.254231.26.6.25530
57231.26.7.0/27231.26.7.1 to 231.26.7.30231.26.7.3130
58231.26.7.32/27231.26.7.33 to 231.26.7.62231.26.7.6330
59231.26.7.64/27231.26.7.65 to 231.26.7.94231.26.7.9530
60231.26.7.96/27231.26.7.97 to 231.26.7.126231.26.7.12730
61231.26.7.128/27231.26.7.129 to 231.26.7.158231.26.7.15930
62231.26.7.160/27231.26.7.161 to 231.26.7.190231.26.7.19130
63231.26.7.192/27231.26.7.193 to 231.26.7.222231.26.7.22330
64231.26.7.224/27231.26.7.225 to 231.26.7.254231.26.7.25530
65231.26.8.0/27231.26.8.1 to 231.26.8.30231.26.8.3130
66231.26.8.32/27231.26.8.33 to 231.26.8.62231.26.8.6330
67231.26.8.64/27231.26.8.65 to 231.26.8.94231.26.8.9530
68231.26.8.96/27231.26.8.97 to 231.26.8.126231.26.8.12730
69231.26.8.128/27231.26.8.129 to 231.26.8.158231.26.8.15930
70231.26.8.160/27231.26.8.161 to 231.26.8.190231.26.8.19130
71231.26.8.192/27231.26.8.193 to 231.26.8.222231.26.8.22330
72231.26.8.224/27231.26.8.225 to 231.26.8.254231.26.8.25530
73231.26.9.0/27231.26.9.1 to 231.26.9.30231.26.9.3130
74231.26.9.32/27231.26.9.33 to 231.26.9.62231.26.9.6330
75231.26.9.64/27231.26.9.65 to 231.26.9.94231.26.9.9530
76231.26.9.96/27231.26.9.97 to 231.26.9.126231.26.9.12730
77231.26.9.128/27231.26.9.129 to 231.26.9.158231.26.9.15930
78231.26.9.160/27231.26.9.161 to 231.26.9.190231.26.9.19130
79231.26.9.192/27231.26.9.193 to 231.26.9.222231.26.9.22330
80231.26.9.224/27231.26.9.225 to 231.26.9.254231.26.9.25530
81231.26.10.0/27231.26.10.1 to 231.26.10.30231.26.10.3130
82231.26.10.32/27231.26.10.33 to 231.26.10.62231.26.10.6330
83231.26.10.64/27231.26.10.65 to 231.26.10.94231.26.10.9530
84231.26.10.96/27231.26.10.97 to 231.26.10.126231.26.10.12730
85231.26.10.128/27231.26.10.129 to 231.26.10.158231.26.10.15930
86231.26.10.160/27231.26.10.161 to 231.26.10.190231.26.10.19130
87231.26.10.192/27231.26.10.193 to 231.26.10.222231.26.10.22330
88231.26.10.224/27231.26.10.225 to 231.26.10.254231.26.10.25530
89231.26.11.0/27231.26.11.1 to 231.26.11.30231.26.11.3130
90231.26.11.32/27231.26.11.33 to 231.26.11.62231.26.11.6330
91231.26.11.64/27231.26.11.65 to 231.26.11.94231.26.11.9530
92231.26.11.96/27231.26.11.97 to 231.26.11.126231.26.11.12730
93231.26.11.128/27231.26.11.129 to 231.26.11.158231.26.11.15930
94231.26.11.160/27231.26.11.161 to 231.26.11.190231.26.11.19130
95231.26.11.192/27231.26.11.193 to 231.26.11.222231.26.11.22330
96231.26.11.224/27231.26.11.225 to 231.26.11.254231.26.11.25530
97231.26.12.0/27231.26.12.1 to 231.26.12.30231.26.12.3130
98231.26.12.32/27231.26.12.33 to 231.26.12.62231.26.12.6330
99231.26.12.64/27231.26.12.65 to 231.26.12.94231.26.12.9530
100231.26.12.96/27231.26.12.97 to 231.26.12.126231.26.12.12730
101231.26.12.128/27231.26.12.129 to 231.26.12.158231.26.12.15930
102231.26.12.160/27231.26.12.161 to 231.26.12.190231.26.12.19130
103231.26.12.192/27231.26.12.193 to 231.26.12.222231.26.12.22330
104231.26.12.224/27231.26.12.225 to 231.26.12.254231.26.12.25530
105231.26.13.0/27231.26.13.1 to 231.26.13.30231.26.13.3130
106231.26.13.32/27231.26.13.33 to 231.26.13.62231.26.13.6330
107231.26.13.64/27231.26.13.65 to 231.26.13.94231.26.13.9530
108231.26.13.96/27231.26.13.97 to 231.26.13.126231.26.13.12730
109231.26.13.128/27231.26.13.129 to 231.26.13.158231.26.13.15930
110231.26.13.160/27231.26.13.161 to 231.26.13.190231.26.13.19130
111231.26.13.192/27231.26.13.193 to 231.26.13.222231.26.13.22330
112231.26.13.224/27231.26.13.225 to 231.26.13.254231.26.13.25530
113231.26.14.0/27231.26.14.1 to 231.26.14.30231.26.14.3130
114231.26.14.32/27231.26.14.33 to 231.26.14.62231.26.14.6330
115231.26.14.64/27231.26.14.65 to 231.26.14.94231.26.14.9530
116231.26.14.96/27231.26.14.97 to 231.26.14.126231.26.14.12730
117231.26.14.128/27231.26.14.129 to 231.26.14.158231.26.14.15930
118231.26.14.160/27231.26.14.161 to 231.26.14.190231.26.14.19130
119231.26.14.192/27231.26.14.193 to 231.26.14.222231.26.14.22330
120231.26.14.224/27231.26.14.225 to 231.26.14.254231.26.14.25530
121231.26.15.0/27231.26.15.1 to 231.26.15.30231.26.15.3130
122231.26.15.32/27231.26.15.33 to 231.26.15.62231.26.15.6330
123231.26.15.64/27231.26.15.65 to 231.26.15.94231.26.15.9530
124231.26.15.96/27231.26.15.97 to 231.26.15.126231.26.15.12730
125231.26.15.128/27231.26.15.129 to 231.26.15.158231.26.15.15930
126231.26.15.160/27231.26.15.161 to 231.26.15.190231.26.15.19130
127231.26.15.192/27231.26.15.193 to 231.26.15.222231.26.15.22330
128231.26.15.224/27231.26.15.225 to 231.26.15.254231.26.15.25530
129231.26.16.0/27231.26.16.1 to 231.26.16.30231.26.16.3130
130231.26.16.32/27231.26.16.33 to 231.26.16.62231.26.16.6330
131231.26.16.64/27231.26.16.65 to 231.26.16.94231.26.16.9530
132231.26.16.96/27231.26.16.97 to 231.26.16.126231.26.16.12730
133231.26.16.128/27231.26.16.129 to 231.26.16.158231.26.16.15930
134231.26.16.160/27231.26.16.161 to 231.26.16.190231.26.16.19130
135231.26.16.192/27231.26.16.193 to 231.26.16.222231.26.16.22330
136231.26.16.224/27231.26.16.225 to 231.26.16.254231.26.16.25530
137231.26.17.0/27231.26.17.1 to 231.26.17.30231.26.17.3130
138231.26.17.32/27231.26.17.33 to 231.26.17.62231.26.17.6330
139231.26.17.64/27231.26.17.65 to 231.26.17.94231.26.17.9530
140231.26.17.96/27231.26.17.97 to 231.26.17.126231.26.17.12730
141231.26.17.128/27231.26.17.129 to 231.26.17.158231.26.17.15930
142231.26.17.160/27231.26.17.161 to 231.26.17.190231.26.17.19130
143231.26.17.192/27231.26.17.193 to 231.26.17.222231.26.17.22330
144231.26.17.224/27231.26.17.225 to 231.26.17.254231.26.17.25530
145231.26.18.0/27231.26.18.1 to 231.26.18.30231.26.18.3130
146231.26.18.32/27231.26.18.33 to 231.26.18.62231.26.18.6330
147231.26.18.64/27231.26.18.65 to 231.26.18.94231.26.18.9530
148231.26.18.96/27231.26.18.97 to 231.26.18.126231.26.18.12730
149231.26.18.128/27231.26.18.129 to 231.26.18.158231.26.18.15930
150231.26.18.160/27231.26.18.161 to 231.26.18.190231.26.18.19130
151231.26.18.192/27231.26.18.193 to 231.26.18.222231.26.18.22330
152231.26.18.224/27231.26.18.225 to 231.26.18.254231.26.18.25530
153231.26.19.0/27231.26.19.1 to 231.26.19.30231.26.19.3130
154231.26.19.32/27231.26.19.33 to 231.26.19.62231.26.19.6330
155231.26.19.64/27231.26.19.65 to 231.26.19.94231.26.19.9530
156231.26.19.96/27231.26.19.97 to 231.26.19.126231.26.19.12730
157231.26.19.128/27231.26.19.129 to 231.26.19.158231.26.19.15930
158231.26.19.160/27231.26.19.161 to 231.26.19.190231.26.19.19130
159231.26.19.192/27231.26.19.193 to 231.26.19.222231.26.19.22330
160231.26.19.224/27231.26.19.225 to 231.26.19.254231.26.19.25530
161231.26.20.0/27231.26.20.1 to 231.26.20.30231.26.20.3130
162231.26.20.32/27231.26.20.33 to 231.26.20.62231.26.20.6330
163231.26.20.64/27231.26.20.65 to 231.26.20.94231.26.20.9530
164231.26.20.96/27231.26.20.97 to 231.26.20.126231.26.20.12730
165231.26.20.128/27231.26.20.129 to 231.26.20.158231.26.20.15930
166231.26.20.160/27231.26.20.161 to 231.26.20.190231.26.20.19130
167231.26.20.192/27231.26.20.193 to 231.26.20.222231.26.20.22330
168231.26.20.224/27231.26.20.225 to 231.26.20.254231.26.20.25530
169231.26.21.0/27231.26.21.1 to 231.26.21.30231.26.21.3130
170231.26.21.32/27231.26.21.33 to 231.26.21.62231.26.21.6330
171231.26.21.64/27231.26.21.65 to 231.26.21.94231.26.21.9530
172231.26.21.96/27231.26.21.97 to 231.26.21.126231.26.21.12730
173231.26.21.128/27231.26.21.129 to 231.26.21.158231.26.21.15930
174231.26.21.160/27231.26.21.161 to 231.26.21.190231.26.21.19130
175231.26.21.192/27231.26.21.193 to 231.26.21.222231.26.21.22330
176231.26.21.224/27231.26.21.225 to 231.26.21.254231.26.21.25530
177231.26.22.0/27231.26.22.1 to 231.26.22.30231.26.22.3130
178231.26.22.32/27231.26.22.33 to 231.26.22.62231.26.22.6330
179231.26.22.64/27231.26.22.65 to 231.26.22.94231.26.22.9530
180231.26.22.96/27231.26.22.97 to 231.26.22.126231.26.22.12730
181231.26.22.128/27231.26.22.129 to 231.26.22.158231.26.22.15930
182231.26.22.160/27231.26.22.161 to 231.26.22.190231.26.22.19130
183231.26.22.192/27231.26.22.193 to 231.26.22.222231.26.22.22330
184231.26.22.224/27231.26.22.225 to 231.26.22.254231.26.22.25530
185231.26.23.0/27231.26.23.1 to 231.26.23.30231.26.23.3130
186231.26.23.32/27231.26.23.33 to 231.26.23.62231.26.23.6330
187231.26.23.64/27231.26.23.65 to 231.26.23.94231.26.23.9530
188231.26.23.96/27231.26.23.97 to 231.26.23.126231.26.23.12730
189231.26.23.128/27231.26.23.129 to 231.26.23.158231.26.23.15930
190231.26.23.160/27231.26.23.161 to 231.26.23.190231.26.23.19130
191231.26.23.192/27231.26.23.193 to 231.26.23.222231.26.23.22330
192231.26.23.224/27231.26.23.225 to 231.26.23.254231.26.23.25530
193231.26.24.0/27231.26.24.1 to 231.26.24.30231.26.24.3130
194231.26.24.32/27231.26.24.33 to 231.26.24.62231.26.24.6330
195231.26.24.64/27231.26.24.65 to 231.26.24.94231.26.24.9530
196231.26.24.96/27231.26.24.97 to 231.26.24.126231.26.24.12730
197231.26.24.128/27231.26.24.129 to 231.26.24.158231.26.24.15930
198231.26.24.160/27231.26.24.161 to 231.26.24.190231.26.24.19130
199231.26.24.192/27231.26.24.193 to 231.26.24.222231.26.24.22330
200231.26.24.224/27231.26.24.225 to 231.26.24.254231.26.24.25530
201231.26.25.0/27231.26.25.1 to 231.26.25.30231.26.25.3130
202231.26.25.32/27231.26.25.33 to 231.26.25.62231.26.25.6330
203231.26.25.64/27231.26.25.65 to 231.26.25.94231.26.25.9530
204231.26.25.96/27231.26.25.97 to 231.26.25.126231.26.25.12730
205231.26.25.128/27231.26.25.129 to 231.26.25.158231.26.25.15930
206231.26.25.160/27231.26.25.161 to 231.26.25.190231.26.25.19130
207231.26.25.192/27231.26.25.193 to 231.26.25.222231.26.25.22330
208231.26.25.224/27231.26.25.225 to 231.26.25.254231.26.25.25530
209231.26.26.0/27231.26.26.1 to 231.26.26.30231.26.26.3130
210231.26.26.32/27231.26.26.33 to 231.26.26.62231.26.26.6330
211231.26.26.64/27231.26.26.65 to 231.26.26.94231.26.26.9530
212231.26.26.96/27231.26.26.97 to 231.26.26.126231.26.26.12730
213231.26.26.128/27231.26.26.129 to 231.26.26.158231.26.26.15930
214231.26.26.160/27231.26.26.161 to 231.26.26.190231.26.26.19130
215231.26.26.192/27231.26.26.193 to 231.26.26.222231.26.26.22330
216231.26.26.224/27231.26.26.225 to 231.26.26.254231.26.26.25530
217231.26.27.0/27231.26.27.1 to 231.26.27.30231.26.27.3130
218231.26.27.32/27231.26.27.33 to 231.26.27.62231.26.27.6330
219231.26.27.64/27231.26.27.65 to 231.26.27.94231.26.27.9530
220231.26.27.96/27231.26.27.97 to 231.26.27.126231.26.27.12730
221231.26.27.128/27231.26.27.129 to 231.26.27.158231.26.27.15930
222231.26.27.160/27231.26.27.161 to 231.26.27.190231.26.27.19130
223231.26.27.192/27231.26.27.193 to 231.26.27.222231.26.27.22330
224231.26.27.224/27231.26.27.225 to 231.26.27.254231.26.27.25530
225231.26.28.0/27231.26.28.1 to 231.26.28.30231.26.28.3130
226231.26.28.32/27231.26.28.33 to 231.26.28.62231.26.28.6330
227231.26.28.64/27231.26.28.65 to 231.26.28.94231.26.28.9530
228231.26.28.96/27231.26.28.97 to 231.26.28.126231.26.28.12730
229231.26.28.128/27231.26.28.129 to 231.26.28.158231.26.28.15930
230231.26.28.160/27231.26.28.161 to 231.26.28.190231.26.28.19130
231231.26.28.192/27231.26.28.193 to 231.26.28.222231.26.28.22330
232231.26.28.224/27231.26.28.225 to 231.26.28.254231.26.28.25530
233231.26.29.0/27231.26.29.1 to 231.26.29.30231.26.29.3130
234231.26.29.32/27231.26.29.33 to 231.26.29.62231.26.29.6330
235231.26.29.64/27231.26.29.65 to 231.26.29.94231.26.29.9530
236231.26.29.96/27231.26.29.97 to 231.26.29.126231.26.29.12730
237231.26.29.128/27231.26.29.129 to 231.26.29.158231.26.29.15930
238231.26.29.160/27231.26.29.161 to 231.26.29.190231.26.29.19130
239231.26.29.192/27231.26.29.193 to 231.26.29.222231.26.29.22330
240231.26.29.224/27231.26.29.225 to 231.26.29.254231.26.29.25530
241231.26.30.0/27231.26.30.1 to 231.26.30.30231.26.30.3130
242231.26.30.32/27231.26.30.33 to 231.26.30.62231.26.30.6330
243231.26.30.64/27231.26.30.65 to 231.26.30.94231.26.30.9530
244231.26.30.96/27231.26.30.97 to 231.26.30.126231.26.30.12730
245231.26.30.128/27231.26.30.129 to 231.26.30.158231.26.30.15930
246231.26.30.160/27231.26.30.161 to 231.26.30.190231.26.30.19130
247231.26.30.192/27231.26.30.193 to 231.26.30.222231.26.30.22330
248231.26.30.224/27231.26.30.225 to 231.26.30.254231.26.30.25530
249231.26.31.0/27231.26.31.1 to 231.26.31.30231.26.31.3130
250231.26.31.32/27231.26.31.33 to 231.26.31.62231.26.31.6330
251231.26.31.64/27231.26.31.65 to 231.26.31.94231.26.31.9530
252231.26.31.96/27231.26.31.97 to 231.26.31.126231.26.31.12730
253231.26.31.128/27231.26.31.129 to 231.26.31.158231.26.31.15930
254231.26.31.160/27231.26.31.161 to 231.26.31.190231.26.31.19130
255231.26.31.192/27231.26.31.193 to 231.26.31.222231.26.31.22330
256231.26.31.224/27231.26.31.225 to 231.26.31.254231.26.31.25530

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.