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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.

Prefix/108
Addresses1,048,576
/64 networksPart of one
Network
::ffff:8.0.0.0/108
First address
::ffff:8.0.0.0
Last address
::ffff:8.15.255.255
Addresses
1,048,576
/64 networks (LANs)
None: smaller than one /64 LAN
Full form
0000:0000:0000:0000:0000:ffff:0800:0000
Type
IPv4-mapped ::ffff:0:0/96
An IPv4 address written as IPv6
IPv4 address inside
8.0.0.0
Reverse DNS zone
0.8.0.f.f.f.f.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa
Split into smaller subnets/124
/109 (2)/110 (4)/111 (8)/112 (16)/116 (256)/120 (4,096)/124 (65,536)

::ffff:8.0.0.0/108 makes 65,536 subnets of /124; the first 256 are listed.

Subnets
#SubnetLast address
1::ffff:8.0.0.0/124::ffff:8.0.0.15
2::ffff:8.0.0.16/124::ffff:8.0.0.31
3::ffff:8.0.0.32/124::ffff:8.0.0.47
4::ffff:8.0.0.48/124::ffff:8.0.0.63
5::ffff:8.0.0.64/124::ffff:8.0.0.79
6::ffff:8.0.0.80/124::ffff:8.0.0.95
7::ffff:8.0.0.96/124::ffff:8.0.0.111
8::ffff:8.0.0.112/124::ffff:8.0.0.127
9::ffff:8.0.0.128/124::ffff:8.0.0.143
10::ffff:8.0.0.144/124::ffff:8.0.0.159
11::ffff:8.0.0.160/124::ffff:8.0.0.175
12::ffff:8.0.0.176/124::ffff:8.0.0.191
13::ffff:8.0.0.192/124::ffff:8.0.0.207
14::ffff:8.0.0.208/124::ffff:8.0.0.223
15::ffff:8.0.0.224/124::ffff:8.0.0.239
16::ffff:8.0.0.240/124::ffff:8.0.0.255
17::ffff:8.0.1.0/124::ffff:8.0.1.15
18::ffff:8.0.1.16/124::ffff:8.0.1.31
19::ffff:8.0.1.32/124::ffff:8.0.1.47
20::ffff:8.0.1.48/124::ffff:8.0.1.63
21::ffff:8.0.1.64/124::ffff:8.0.1.79
22::ffff:8.0.1.80/124::ffff:8.0.1.95
23::ffff:8.0.1.96/124::ffff:8.0.1.111
24::ffff:8.0.1.112/124::ffff:8.0.1.127
25::ffff:8.0.1.128/124::ffff:8.0.1.143
26::ffff:8.0.1.144/124::ffff:8.0.1.159
27::ffff:8.0.1.160/124::ffff:8.0.1.175
28::ffff:8.0.1.176/124::ffff:8.0.1.191
29::ffff:8.0.1.192/124::ffff:8.0.1.207
30::ffff:8.0.1.208/124::ffff:8.0.1.223
31::ffff:8.0.1.224/124::ffff:8.0.1.239
32::ffff:8.0.1.240/124::ffff:8.0.1.255
33::ffff:8.0.2.0/124::ffff:8.0.2.15
34::ffff:8.0.2.16/124::ffff:8.0.2.31
35::ffff:8.0.2.32/124::ffff:8.0.2.47
36::ffff:8.0.2.48/124::ffff:8.0.2.63
37::ffff:8.0.2.64/124::ffff:8.0.2.79
38::ffff:8.0.2.80/124::ffff:8.0.2.95
39::ffff:8.0.2.96/124::ffff:8.0.2.111
40::ffff:8.0.2.112/124::ffff:8.0.2.127
41::ffff:8.0.2.128/124::ffff:8.0.2.143
42::ffff:8.0.2.144/124::ffff:8.0.2.159
43::ffff:8.0.2.160/124::ffff:8.0.2.175
44::ffff:8.0.2.176/124::ffff:8.0.2.191
45::ffff:8.0.2.192/124::ffff:8.0.2.207
46::ffff:8.0.2.208/124::ffff:8.0.2.223
47::ffff:8.0.2.224/124::ffff:8.0.2.239
48::ffff:8.0.2.240/124::ffff:8.0.2.255
49::ffff:8.0.3.0/124::ffff:8.0.3.15
50::ffff:8.0.3.16/124::ffff:8.0.3.31
51::ffff:8.0.3.32/124::ffff:8.0.3.47
52::ffff:8.0.3.48/124::ffff:8.0.3.63
53::ffff:8.0.3.64/124::ffff:8.0.3.79
54::ffff:8.0.3.80/124::ffff:8.0.3.95
55::ffff:8.0.3.96/124::ffff:8.0.3.111
56::ffff:8.0.3.112/124::ffff:8.0.3.127
57::ffff:8.0.3.128/124::ffff:8.0.3.143
58::ffff:8.0.3.144/124::ffff:8.0.3.159
59::ffff:8.0.3.160/124::ffff:8.0.3.175
60::ffff:8.0.3.176/124::ffff:8.0.3.191
61::ffff:8.0.3.192/124::ffff:8.0.3.207
62::ffff:8.0.3.208/124::ffff:8.0.3.223
63::ffff:8.0.3.224/124::ffff:8.0.3.239
64::ffff:8.0.3.240/124::ffff:8.0.3.255
65::ffff:8.0.4.0/124::ffff:8.0.4.15
66::ffff:8.0.4.16/124::ffff:8.0.4.31
67::ffff:8.0.4.32/124::ffff:8.0.4.47
68::ffff:8.0.4.48/124::ffff:8.0.4.63
69::ffff:8.0.4.64/124::ffff:8.0.4.79
70::ffff:8.0.4.80/124::ffff:8.0.4.95
71::ffff:8.0.4.96/124::ffff:8.0.4.111
72::ffff:8.0.4.112/124::ffff:8.0.4.127
73::ffff:8.0.4.128/124::ffff:8.0.4.143
74::ffff:8.0.4.144/124::ffff:8.0.4.159
75::ffff:8.0.4.160/124::ffff:8.0.4.175
76::ffff:8.0.4.176/124::ffff:8.0.4.191
77::ffff:8.0.4.192/124::ffff:8.0.4.207
78::ffff:8.0.4.208/124::ffff:8.0.4.223
79::ffff:8.0.4.224/124::ffff:8.0.4.239
80::ffff:8.0.4.240/124::ffff:8.0.4.255
81::ffff:8.0.5.0/124::ffff:8.0.5.15
82::ffff:8.0.5.16/124::ffff:8.0.5.31
83::ffff:8.0.5.32/124::ffff:8.0.5.47
84::ffff:8.0.5.48/124::ffff:8.0.5.63
85::ffff:8.0.5.64/124::ffff:8.0.5.79
86::ffff:8.0.5.80/124::ffff:8.0.5.95
87::ffff:8.0.5.96/124::ffff:8.0.5.111
88::ffff:8.0.5.112/124::ffff:8.0.5.127
89::ffff:8.0.5.128/124::ffff:8.0.5.143
90::ffff:8.0.5.144/124::ffff:8.0.5.159
91::ffff:8.0.5.160/124::ffff:8.0.5.175
92::ffff:8.0.5.176/124::ffff:8.0.5.191
93::ffff:8.0.5.192/124::ffff:8.0.5.207
94::ffff:8.0.5.208/124::ffff:8.0.5.223
95::ffff:8.0.5.224/124::ffff:8.0.5.239
96::ffff:8.0.5.240/124::ffff:8.0.5.255
97::ffff:8.0.6.0/124::ffff:8.0.6.15
98::ffff:8.0.6.16/124::ffff:8.0.6.31
99::ffff:8.0.6.32/124::ffff:8.0.6.47
100::ffff:8.0.6.48/124::ffff:8.0.6.63
101::ffff:8.0.6.64/124::ffff:8.0.6.79
102::ffff:8.0.6.80/124::ffff:8.0.6.95
103::ffff:8.0.6.96/124::ffff:8.0.6.111
104::ffff:8.0.6.112/124::ffff:8.0.6.127
105::ffff:8.0.6.128/124::ffff:8.0.6.143
106::ffff:8.0.6.144/124::ffff:8.0.6.159
107::ffff:8.0.6.160/124::ffff:8.0.6.175
108::ffff:8.0.6.176/124::ffff:8.0.6.191
109::ffff:8.0.6.192/124::ffff:8.0.6.207
110::ffff:8.0.6.208/124::ffff:8.0.6.223
111::ffff:8.0.6.224/124::ffff:8.0.6.239
112::ffff:8.0.6.240/124::ffff:8.0.6.255
113::ffff:8.0.7.0/124::ffff:8.0.7.15
114::ffff:8.0.7.16/124::ffff:8.0.7.31
115::ffff:8.0.7.32/124::ffff:8.0.7.47
116::ffff:8.0.7.48/124::ffff:8.0.7.63
117::ffff:8.0.7.64/124::ffff:8.0.7.79
118::ffff:8.0.7.80/124::ffff:8.0.7.95
119::ffff:8.0.7.96/124::ffff:8.0.7.111
120::ffff:8.0.7.112/124::ffff:8.0.7.127
121::ffff:8.0.7.128/124::ffff:8.0.7.143
122::ffff:8.0.7.144/124::ffff:8.0.7.159
123::ffff:8.0.7.160/124::ffff:8.0.7.175
124::ffff:8.0.7.176/124::ffff:8.0.7.191
125::ffff:8.0.7.192/124::ffff:8.0.7.207
126::ffff:8.0.7.208/124::ffff:8.0.7.223
127::ffff:8.0.7.224/124::ffff:8.0.7.239
128::ffff:8.0.7.240/124::ffff:8.0.7.255
129::ffff:8.0.8.0/124::ffff:8.0.8.15
130::ffff:8.0.8.16/124::ffff:8.0.8.31
131::ffff:8.0.8.32/124::ffff:8.0.8.47
132::ffff:8.0.8.48/124::ffff:8.0.8.63
133::ffff:8.0.8.64/124::ffff:8.0.8.79
134::ffff:8.0.8.80/124::ffff:8.0.8.95
135::ffff:8.0.8.96/124::ffff:8.0.8.111
136::ffff:8.0.8.112/124::ffff:8.0.8.127
137::ffff:8.0.8.128/124::ffff:8.0.8.143
138::ffff:8.0.8.144/124::ffff:8.0.8.159
139::ffff:8.0.8.160/124::ffff:8.0.8.175
140::ffff:8.0.8.176/124::ffff:8.0.8.191
141::ffff:8.0.8.192/124::ffff:8.0.8.207
142::ffff:8.0.8.208/124::ffff:8.0.8.223
143::ffff:8.0.8.224/124::ffff:8.0.8.239
144::ffff:8.0.8.240/124::ffff:8.0.8.255
145::ffff:8.0.9.0/124::ffff:8.0.9.15
146::ffff:8.0.9.16/124::ffff:8.0.9.31
147::ffff:8.0.9.32/124::ffff:8.0.9.47
148::ffff:8.0.9.48/124::ffff:8.0.9.63
149::ffff:8.0.9.64/124::ffff:8.0.9.79
150::ffff:8.0.9.80/124::ffff:8.0.9.95
151::ffff:8.0.9.96/124::ffff:8.0.9.111
152::ffff:8.0.9.112/124::ffff:8.0.9.127
153::ffff:8.0.9.128/124::ffff:8.0.9.143
154::ffff:8.0.9.144/124::ffff:8.0.9.159
155::ffff:8.0.9.160/124::ffff:8.0.9.175
156::ffff:8.0.9.176/124::ffff:8.0.9.191
157::ffff:8.0.9.192/124::ffff:8.0.9.207
158::ffff:8.0.9.208/124::ffff:8.0.9.223
159::ffff:8.0.9.224/124::ffff:8.0.9.239
160::ffff:8.0.9.240/124::ffff:8.0.9.255
161::ffff:8.0.10.0/124::ffff:8.0.10.15
162::ffff:8.0.10.16/124::ffff:8.0.10.31
163::ffff:8.0.10.32/124::ffff:8.0.10.47
164::ffff:8.0.10.48/124::ffff:8.0.10.63
165::ffff:8.0.10.64/124::ffff:8.0.10.79
166::ffff:8.0.10.80/124::ffff:8.0.10.95
167::ffff:8.0.10.96/124::ffff:8.0.10.111
168::ffff:8.0.10.112/124::ffff:8.0.10.127
169::ffff:8.0.10.128/124::ffff:8.0.10.143
170::ffff:8.0.10.144/124::ffff:8.0.10.159
171::ffff:8.0.10.160/124::ffff:8.0.10.175
172::ffff:8.0.10.176/124::ffff:8.0.10.191
173::ffff:8.0.10.192/124::ffff:8.0.10.207
174::ffff:8.0.10.208/124::ffff:8.0.10.223
175::ffff:8.0.10.224/124::ffff:8.0.10.239
176::ffff:8.0.10.240/124::ffff:8.0.10.255
177::ffff:8.0.11.0/124::ffff:8.0.11.15
178::ffff:8.0.11.16/124::ffff:8.0.11.31
179::ffff:8.0.11.32/124::ffff:8.0.11.47
180::ffff:8.0.11.48/124::ffff:8.0.11.63
181::ffff:8.0.11.64/124::ffff:8.0.11.79
182::ffff:8.0.11.80/124::ffff:8.0.11.95
183::ffff:8.0.11.96/124::ffff:8.0.11.111
184::ffff:8.0.11.112/124::ffff:8.0.11.127
185::ffff:8.0.11.128/124::ffff:8.0.11.143
186::ffff:8.0.11.144/124::ffff:8.0.11.159
187::ffff:8.0.11.160/124::ffff:8.0.11.175
188::ffff:8.0.11.176/124::ffff:8.0.11.191
189::ffff:8.0.11.192/124::ffff:8.0.11.207
190::ffff:8.0.11.208/124::ffff:8.0.11.223
191::ffff:8.0.11.224/124::ffff:8.0.11.239
192::ffff:8.0.11.240/124::ffff:8.0.11.255
193::ffff:8.0.12.0/124::ffff:8.0.12.15
194::ffff:8.0.12.16/124::ffff:8.0.12.31
195::ffff:8.0.12.32/124::ffff:8.0.12.47
196::ffff:8.0.12.48/124::ffff:8.0.12.63
197::ffff:8.0.12.64/124::ffff:8.0.12.79
198::ffff:8.0.12.80/124::ffff:8.0.12.95
199::ffff:8.0.12.96/124::ffff:8.0.12.111
200::ffff:8.0.12.112/124::ffff:8.0.12.127
201::ffff:8.0.12.128/124::ffff:8.0.12.143
202::ffff:8.0.12.144/124::ffff:8.0.12.159
203::ffff:8.0.12.160/124::ffff:8.0.12.175
204::ffff:8.0.12.176/124::ffff:8.0.12.191
205::ffff:8.0.12.192/124::ffff:8.0.12.207
206::ffff:8.0.12.208/124::ffff:8.0.12.223
207::ffff:8.0.12.224/124::ffff:8.0.12.239
208::ffff:8.0.12.240/124::ffff:8.0.12.255
209::ffff:8.0.13.0/124::ffff:8.0.13.15
210::ffff:8.0.13.16/124::ffff:8.0.13.31
211::ffff:8.0.13.32/124::ffff:8.0.13.47
212::ffff:8.0.13.48/124::ffff:8.0.13.63
213::ffff:8.0.13.64/124::ffff:8.0.13.79
214::ffff:8.0.13.80/124::ffff:8.0.13.95
215::ffff:8.0.13.96/124::ffff:8.0.13.111
216::ffff:8.0.13.112/124::ffff:8.0.13.127
217::ffff:8.0.13.128/124::ffff:8.0.13.143
218::ffff:8.0.13.144/124::ffff:8.0.13.159
219::ffff:8.0.13.160/124::ffff:8.0.13.175
220::ffff:8.0.13.176/124::ffff:8.0.13.191
221::ffff:8.0.13.192/124::ffff:8.0.13.207
222::ffff:8.0.13.208/124::ffff:8.0.13.223
223::ffff:8.0.13.224/124::ffff:8.0.13.239
224::ffff:8.0.13.240/124::ffff:8.0.13.255
225::ffff:8.0.14.0/124::ffff:8.0.14.15
226::ffff:8.0.14.16/124::ffff:8.0.14.31
227::ffff:8.0.14.32/124::ffff:8.0.14.47
228::ffff:8.0.14.48/124::ffff:8.0.14.63
229::ffff:8.0.14.64/124::ffff:8.0.14.79
230::ffff:8.0.14.80/124::ffff:8.0.14.95
231::ffff:8.0.14.96/124::ffff:8.0.14.111
232::ffff:8.0.14.112/124::ffff:8.0.14.127
233::ffff:8.0.14.128/124::ffff:8.0.14.143
234::ffff:8.0.14.144/124::ffff:8.0.14.159
235::ffff:8.0.14.160/124::ffff:8.0.14.175
236::ffff:8.0.14.176/124::ffff:8.0.14.191
237::ffff:8.0.14.192/124::ffff:8.0.14.207
238::ffff:8.0.14.208/124::ffff:8.0.14.223
239::ffff:8.0.14.224/124::ffff:8.0.14.239
240::ffff:8.0.14.240/124::ffff:8.0.14.255
241::ffff:8.0.15.0/124::ffff:8.0.15.15
242::ffff:8.0.15.16/124::ffff:8.0.15.31
243::ffff:8.0.15.32/124::ffff:8.0.15.47
244::ffff:8.0.15.48/124::ffff:8.0.15.63
245::ffff:8.0.15.64/124::ffff:8.0.15.79
246::ffff:8.0.15.80/124::ffff:8.0.15.95
247::ffff:8.0.15.96/124::ffff:8.0.15.111
248::ffff:8.0.15.112/124::ffff:8.0.15.127
249::ffff:8.0.15.128/124::ffff:8.0.15.143
250::ffff:8.0.15.144/124::ffff:8.0.15.159
251::ffff:8.0.15.160/124::ffff:8.0.15.175
252::ffff:8.0.15.176/124::ffff:8.0.15.191
253::ffff:8.0.15.192/124::ffff:8.0.15.207
254::ffff:8.0.15.208/124::ffff:8.0.15.223
255::ffff:8.0.15.224/124::ffff:8.0.15.239
256::ffff:8.0.15.240/124::ffff:8.0.15.255

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.