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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.

Network66.2.128.0/17
Usable hosts32,766
Subnet mask255.255.128.0
Addresses32,768
Network address
66.2.128.0
Broadcast address
66.2.255.255
First usable
66.2.128.1
Last usable
66.2.255.254
Usable hosts
32,766 (32,768 less the network and broadcast addresses)
Subnet mask
255.255.128.0
Wildcard mask
0.0.127.255 (Cisco ACLs, OSPF)
Prefix length
/17
Type
Public public
Old class
A (default /8)
As numbers
Hex 42028000 · Integer 1107460096 to 1107492863
Reverse DNS zones
128.2.66.in-addr.arpa
129.2.66.in-addr.arpa
130.2.66.in-addr.arpa
131.2.66.in-addr.arpa
132.2.66.in-addr.arpa
133.2.66.in-addr.arpa
134.2.66.in-addr.arpa
135.2.66.in-addr.arpa
136.2.66.in-addr.arpa
137.2.66.in-addr.arpa
138.2.66.in-addr.arpa
139.2.66.in-addr.arpa
140.2.66.in-addr.arpa
141.2.66.in-addr.arpa
142.2.66.in-addr.arpa
143.2.66.in-addr.arpa
and 112 more
/17 is not on a 8-bit boundary, so it takes 128 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address01000010.00000010.10000000.0000000066.2.128.0
Subnet mask11111111.11111111.10000000.00000000255.255.128.0
Network01000010.00000010.10000000.0000000066.2.128.0
Broadcast01000010.00000010.11111111.1111111166.2.255.255
Split into smaller subnets/28
/18 (2)/19 (4)/20 (8)/21 (16)/22 (32)/23 (64)/24 (128)/25 (256)/26 (512)/27 (1,024)/28 (2,048)/29 (4,096)

66.2.128.0/17 makes 2,048 subnets of /28; the first 256 are listed.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
166.2.128.0/2866.2.128.1 to 66.2.128.1466.2.128.1514
266.2.128.16/2866.2.128.17 to 66.2.128.3066.2.128.3114
366.2.128.32/2866.2.128.33 to 66.2.128.4666.2.128.4714
466.2.128.48/2866.2.128.49 to 66.2.128.6266.2.128.6314
566.2.128.64/2866.2.128.65 to 66.2.128.7866.2.128.7914
666.2.128.80/2866.2.128.81 to 66.2.128.9466.2.128.9514
766.2.128.96/2866.2.128.97 to 66.2.128.11066.2.128.11114
866.2.128.112/2866.2.128.113 to 66.2.128.12666.2.128.12714
966.2.128.128/2866.2.128.129 to 66.2.128.14266.2.128.14314
1066.2.128.144/2866.2.128.145 to 66.2.128.15866.2.128.15914
1166.2.128.160/2866.2.128.161 to 66.2.128.17466.2.128.17514
1266.2.128.176/2866.2.128.177 to 66.2.128.19066.2.128.19114
1366.2.128.192/2866.2.128.193 to 66.2.128.20666.2.128.20714
1466.2.128.208/2866.2.128.209 to 66.2.128.22266.2.128.22314
1566.2.128.224/2866.2.128.225 to 66.2.128.23866.2.128.23914
1666.2.128.240/2866.2.128.241 to 66.2.128.25466.2.128.25514
1766.2.129.0/2866.2.129.1 to 66.2.129.1466.2.129.1514
1866.2.129.16/2866.2.129.17 to 66.2.129.3066.2.129.3114
1966.2.129.32/2866.2.129.33 to 66.2.129.4666.2.129.4714
2066.2.129.48/2866.2.129.49 to 66.2.129.6266.2.129.6314
2166.2.129.64/2866.2.129.65 to 66.2.129.7866.2.129.7914
2266.2.129.80/2866.2.129.81 to 66.2.129.9466.2.129.9514
2366.2.129.96/2866.2.129.97 to 66.2.129.11066.2.129.11114
2466.2.129.112/2866.2.129.113 to 66.2.129.12666.2.129.12714
2566.2.129.128/2866.2.129.129 to 66.2.129.14266.2.129.14314
2666.2.129.144/2866.2.129.145 to 66.2.129.15866.2.129.15914
2766.2.129.160/2866.2.129.161 to 66.2.129.17466.2.129.17514
2866.2.129.176/2866.2.129.177 to 66.2.129.19066.2.129.19114
2966.2.129.192/2866.2.129.193 to 66.2.129.20666.2.129.20714
3066.2.129.208/2866.2.129.209 to 66.2.129.22266.2.129.22314
3166.2.129.224/2866.2.129.225 to 66.2.129.23866.2.129.23914
3266.2.129.240/2866.2.129.241 to 66.2.129.25466.2.129.25514
3366.2.130.0/2866.2.130.1 to 66.2.130.1466.2.130.1514
3466.2.130.16/2866.2.130.17 to 66.2.130.3066.2.130.3114
3566.2.130.32/2866.2.130.33 to 66.2.130.4666.2.130.4714
3666.2.130.48/2866.2.130.49 to 66.2.130.6266.2.130.6314
3766.2.130.64/2866.2.130.65 to 66.2.130.7866.2.130.7914
3866.2.130.80/2866.2.130.81 to 66.2.130.9466.2.130.9514
3966.2.130.96/2866.2.130.97 to 66.2.130.11066.2.130.11114
4066.2.130.112/2866.2.130.113 to 66.2.130.12666.2.130.12714
4166.2.130.128/2866.2.130.129 to 66.2.130.14266.2.130.14314
4266.2.130.144/2866.2.130.145 to 66.2.130.15866.2.130.15914
4366.2.130.160/2866.2.130.161 to 66.2.130.17466.2.130.17514
4466.2.130.176/2866.2.130.177 to 66.2.130.19066.2.130.19114
4566.2.130.192/2866.2.130.193 to 66.2.130.20666.2.130.20714
4666.2.130.208/2866.2.130.209 to 66.2.130.22266.2.130.22314
4766.2.130.224/2866.2.130.225 to 66.2.130.23866.2.130.23914
4866.2.130.240/2866.2.130.241 to 66.2.130.25466.2.130.25514
4966.2.131.0/2866.2.131.1 to 66.2.131.1466.2.131.1514
5066.2.131.16/2866.2.131.17 to 66.2.131.3066.2.131.3114
5166.2.131.32/2866.2.131.33 to 66.2.131.4666.2.131.4714
5266.2.131.48/2866.2.131.49 to 66.2.131.6266.2.131.6314
5366.2.131.64/2866.2.131.65 to 66.2.131.7866.2.131.7914
5466.2.131.80/2866.2.131.81 to 66.2.131.9466.2.131.9514
5566.2.131.96/2866.2.131.97 to 66.2.131.11066.2.131.11114
5666.2.131.112/2866.2.131.113 to 66.2.131.12666.2.131.12714
5766.2.131.128/2866.2.131.129 to 66.2.131.14266.2.131.14314
5866.2.131.144/2866.2.131.145 to 66.2.131.15866.2.131.15914
5966.2.131.160/2866.2.131.161 to 66.2.131.17466.2.131.17514
6066.2.131.176/2866.2.131.177 to 66.2.131.19066.2.131.19114
6166.2.131.192/2866.2.131.193 to 66.2.131.20666.2.131.20714
6266.2.131.208/2866.2.131.209 to 66.2.131.22266.2.131.22314
6366.2.131.224/2866.2.131.225 to 66.2.131.23866.2.131.23914
6466.2.131.240/2866.2.131.241 to 66.2.131.25466.2.131.25514
6566.2.132.0/2866.2.132.1 to 66.2.132.1466.2.132.1514
6666.2.132.16/2866.2.132.17 to 66.2.132.3066.2.132.3114
6766.2.132.32/2866.2.132.33 to 66.2.132.4666.2.132.4714
6866.2.132.48/2866.2.132.49 to 66.2.132.6266.2.132.6314
6966.2.132.64/2866.2.132.65 to 66.2.132.7866.2.132.7914
7066.2.132.80/2866.2.132.81 to 66.2.132.9466.2.132.9514
7166.2.132.96/2866.2.132.97 to 66.2.132.11066.2.132.11114
7266.2.132.112/2866.2.132.113 to 66.2.132.12666.2.132.12714
7366.2.132.128/2866.2.132.129 to 66.2.132.14266.2.132.14314
7466.2.132.144/2866.2.132.145 to 66.2.132.15866.2.132.15914
7566.2.132.160/2866.2.132.161 to 66.2.132.17466.2.132.17514
7666.2.132.176/2866.2.132.177 to 66.2.132.19066.2.132.19114
7766.2.132.192/2866.2.132.193 to 66.2.132.20666.2.132.20714
7866.2.132.208/2866.2.132.209 to 66.2.132.22266.2.132.22314
7966.2.132.224/2866.2.132.225 to 66.2.132.23866.2.132.23914
8066.2.132.240/2866.2.132.241 to 66.2.132.25466.2.132.25514
8166.2.133.0/2866.2.133.1 to 66.2.133.1466.2.133.1514
8266.2.133.16/2866.2.133.17 to 66.2.133.3066.2.133.3114
8366.2.133.32/2866.2.133.33 to 66.2.133.4666.2.133.4714
8466.2.133.48/2866.2.133.49 to 66.2.133.6266.2.133.6314
8566.2.133.64/2866.2.133.65 to 66.2.133.7866.2.133.7914
8666.2.133.80/2866.2.133.81 to 66.2.133.9466.2.133.9514
8766.2.133.96/2866.2.133.97 to 66.2.133.11066.2.133.11114
8866.2.133.112/2866.2.133.113 to 66.2.133.12666.2.133.12714
8966.2.133.128/2866.2.133.129 to 66.2.133.14266.2.133.14314
9066.2.133.144/2866.2.133.145 to 66.2.133.15866.2.133.15914
9166.2.133.160/2866.2.133.161 to 66.2.133.17466.2.133.17514
9266.2.133.176/2866.2.133.177 to 66.2.133.19066.2.133.19114
9366.2.133.192/2866.2.133.193 to 66.2.133.20666.2.133.20714
9466.2.133.208/2866.2.133.209 to 66.2.133.22266.2.133.22314
9566.2.133.224/2866.2.133.225 to 66.2.133.23866.2.133.23914
9666.2.133.240/2866.2.133.241 to 66.2.133.25466.2.133.25514
9766.2.134.0/2866.2.134.1 to 66.2.134.1466.2.134.1514
9866.2.134.16/2866.2.134.17 to 66.2.134.3066.2.134.3114
9966.2.134.32/2866.2.134.33 to 66.2.134.4666.2.134.4714
10066.2.134.48/2866.2.134.49 to 66.2.134.6266.2.134.6314
10166.2.134.64/2866.2.134.65 to 66.2.134.7866.2.134.7914
10266.2.134.80/2866.2.134.81 to 66.2.134.9466.2.134.9514
10366.2.134.96/2866.2.134.97 to 66.2.134.11066.2.134.11114
10466.2.134.112/2866.2.134.113 to 66.2.134.12666.2.134.12714
10566.2.134.128/2866.2.134.129 to 66.2.134.14266.2.134.14314
10666.2.134.144/2866.2.134.145 to 66.2.134.15866.2.134.15914
10766.2.134.160/2866.2.134.161 to 66.2.134.17466.2.134.17514
10866.2.134.176/2866.2.134.177 to 66.2.134.19066.2.134.19114
10966.2.134.192/2866.2.134.193 to 66.2.134.20666.2.134.20714
11066.2.134.208/2866.2.134.209 to 66.2.134.22266.2.134.22314
11166.2.134.224/2866.2.134.225 to 66.2.134.23866.2.134.23914
11266.2.134.240/2866.2.134.241 to 66.2.134.25466.2.134.25514
11366.2.135.0/2866.2.135.1 to 66.2.135.1466.2.135.1514
11466.2.135.16/2866.2.135.17 to 66.2.135.3066.2.135.3114
11566.2.135.32/2866.2.135.33 to 66.2.135.4666.2.135.4714
11666.2.135.48/2866.2.135.49 to 66.2.135.6266.2.135.6314
11766.2.135.64/2866.2.135.65 to 66.2.135.7866.2.135.7914
11866.2.135.80/2866.2.135.81 to 66.2.135.9466.2.135.9514
11966.2.135.96/2866.2.135.97 to 66.2.135.11066.2.135.11114
12066.2.135.112/2866.2.135.113 to 66.2.135.12666.2.135.12714
12166.2.135.128/2866.2.135.129 to 66.2.135.14266.2.135.14314
12266.2.135.144/2866.2.135.145 to 66.2.135.15866.2.135.15914
12366.2.135.160/2866.2.135.161 to 66.2.135.17466.2.135.17514
12466.2.135.176/2866.2.135.177 to 66.2.135.19066.2.135.19114
12566.2.135.192/2866.2.135.193 to 66.2.135.20666.2.135.20714
12666.2.135.208/2866.2.135.209 to 66.2.135.22266.2.135.22314
12766.2.135.224/2866.2.135.225 to 66.2.135.23866.2.135.23914
12866.2.135.240/2866.2.135.241 to 66.2.135.25466.2.135.25514
12966.2.136.0/2866.2.136.1 to 66.2.136.1466.2.136.1514
13066.2.136.16/2866.2.136.17 to 66.2.136.3066.2.136.3114
13166.2.136.32/2866.2.136.33 to 66.2.136.4666.2.136.4714
13266.2.136.48/2866.2.136.49 to 66.2.136.6266.2.136.6314
13366.2.136.64/2866.2.136.65 to 66.2.136.7866.2.136.7914
13466.2.136.80/2866.2.136.81 to 66.2.136.9466.2.136.9514
13566.2.136.96/2866.2.136.97 to 66.2.136.11066.2.136.11114
13666.2.136.112/2866.2.136.113 to 66.2.136.12666.2.136.12714
13766.2.136.128/2866.2.136.129 to 66.2.136.14266.2.136.14314
13866.2.136.144/2866.2.136.145 to 66.2.136.15866.2.136.15914
13966.2.136.160/2866.2.136.161 to 66.2.136.17466.2.136.17514
14066.2.136.176/2866.2.136.177 to 66.2.136.19066.2.136.19114
14166.2.136.192/2866.2.136.193 to 66.2.136.20666.2.136.20714
14266.2.136.208/2866.2.136.209 to 66.2.136.22266.2.136.22314
14366.2.136.224/2866.2.136.225 to 66.2.136.23866.2.136.23914
14466.2.136.240/2866.2.136.241 to 66.2.136.25466.2.136.25514
14566.2.137.0/2866.2.137.1 to 66.2.137.1466.2.137.1514
14666.2.137.16/2866.2.137.17 to 66.2.137.3066.2.137.3114
14766.2.137.32/2866.2.137.33 to 66.2.137.4666.2.137.4714
14866.2.137.48/2866.2.137.49 to 66.2.137.6266.2.137.6314
14966.2.137.64/2866.2.137.65 to 66.2.137.7866.2.137.7914
15066.2.137.80/2866.2.137.81 to 66.2.137.9466.2.137.9514
15166.2.137.96/2866.2.137.97 to 66.2.137.11066.2.137.11114
15266.2.137.112/2866.2.137.113 to 66.2.137.12666.2.137.12714
15366.2.137.128/2866.2.137.129 to 66.2.137.14266.2.137.14314
15466.2.137.144/2866.2.137.145 to 66.2.137.15866.2.137.15914
15566.2.137.160/2866.2.137.161 to 66.2.137.17466.2.137.17514
15666.2.137.176/2866.2.137.177 to 66.2.137.19066.2.137.19114
15766.2.137.192/2866.2.137.193 to 66.2.137.20666.2.137.20714
15866.2.137.208/2866.2.137.209 to 66.2.137.22266.2.137.22314
15966.2.137.224/2866.2.137.225 to 66.2.137.23866.2.137.23914
16066.2.137.240/2866.2.137.241 to 66.2.137.25466.2.137.25514
16166.2.138.0/2866.2.138.1 to 66.2.138.1466.2.138.1514
16266.2.138.16/2866.2.138.17 to 66.2.138.3066.2.138.3114
16366.2.138.32/2866.2.138.33 to 66.2.138.4666.2.138.4714
16466.2.138.48/2866.2.138.49 to 66.2.138.6266.2.138.6314
16566.2.138.64/2866.2.138.65 to 66.2.138.7866.2.138.7914
16666.2.138.80/2866.2.138.81 to 66.2.138.9466.2.138.9514
16766.2.138.96/2866.2.138.97 to 66.2.138.11066.2.138.11114
16866.2.138.112/2866.2.138.113 to 66.2.138.12666.2.138.12714
16966.2.138.128/2866.2.138.129 to 66.2.138.14266.2.138.14314
17066.2.138.144/2866.2.138.145 to 66.2.138.15866.2.138.15914
17166.2.138.160/2866.2.138.161 to 66.2.138.17466.2.138.17514
17266.2.138.176/2866.2.138.177 to 66.2.138.19066.2.138.19114
17366.2.138.192/2866.2.138.193 to 66.2.138.20666.2.138.20714
17466.2.138.208/2866.2.138.209 to 66.2.138.22266.2.138.22314
17566.2.138.224/2866.2.138.225 to 66.2.138.23866.2.138.23914
17666.2.138.240/2866.2.138.241 to 66.2.138.25466.2.138.25514
17766.2.139.0/2866.2.139.1 to 66.2.139.1466.2.139.1514
17866.2.139.16/2866.2.139.17 to 66.2.139.3066.2.139.3114
17966.2.139.32/2866.2.139.33 to 66.2.139.4666.2.139.4714
18066.2.139.48/2866.2.139.49 to 66.2.139.6266.2.139.6314
18166.2.139.64/2866.2.139.65 to 66.2.139.7866.2.139.7914
18266.2.139.80/2866.2.139.81 to 66.2.139.9466.2.139.9514
18366.2.139.96/2866.2.139.97 to 66.2.139.11066.2.139.11114
18466.2.139.112/2866.2.139.113 to 66.2.139.12666.2.139.12714
18566.2.139.128/2866.2.139.129 to 66.2.139.14266.2.139.14314
18666.2.139.144/2866.2.139.145 to 66.2.139.15866.2.139.15914
18766.2.139.160/2866.2.139.161 to 66.2.139.17466.2.139.17514
18866.2.139.176/2866.2.139.177 to 66.2.139.19066.2.139.19114
18966.2.139.192/2866.2.139.193 to 66.2.139.20666.2.139.20714
19066.2.139.208/2866.2.139.209 to 66.2.139.22266.2.139.22314
19166.2.139.224/2866.2.139.225 to 66.2.139.23866.2.139.23914
19266.2.139.240/2866.2.139.241 to 66.2.139.25466.2.139.25514
19366.2.140.0/2866.2.140.1 to 66.2.140.1466.2.140.1514
19466.2.140.16/2866.2.140.17 to 66.2.140.3066.2.140.3114
19566.2.140.32/2866.2.140.33 to 66.2.140.4666.2.140.4714
19666.2.140.48/2866.2.140.49 to 66.2.140.6266.2.140.6314
19766.2.140.64/2866.2.140.65 to 66.2.140.7866.2.140.7914
19866.2.140.80/2866.2.140.81 to 66.2.140.9466.2.140.9514
19966.2.140.96/2866.2.140.97 to 66.2.140.11066.2.140.11114
20066.2.140.112/2866.2.140.113 to 66.2.140.12666.2.140.12714
20166.2.140.128/2866.2.140.129 to 66.2.140.14266.2.140.14314
20266.2.140.144/2866.2.140.145 to 66.2.140.15866.2.140.15914
20366.2.140.160/2866.2.140.161 to 66.2.140.17466.2.140.17514
20466.2.140.176/2866.2.140.177 to 66.2.140.19066.2.140.19114
20566.2.140.192/2866.2.140.193 to 66.2.140.20666.2.140.20714
20666.2.140.208/2866.2.140.209 to 66.2.140.22266.2.140.22314
20766.2.140.224/2866.2.140.225 to 66.2.140.23866.2.140.23914
20866.2.140.240/2866.2.140.241 to 66.2.140.25466.2.140.25514
20966.2.141.0/2866.2.141.1 to 66.2.141.1466.2.141.1514
21066.2.141.16/2866.2.141.17 to 66.2.141.3066.2.141.3114
21166.2.141.32/2866.2.141.33 to 66.2.141.4666.2.141.4714
21266.2.141.48/2866.2.141.49 to 66.2.141.6266.2.141.6314
21366.2.141.64/2866.2.141.65 to 66.2.141.7866.2.141.7914
21466.2.141.80/2866.2.141.81 to 66.2.141.9466.2.141.9514
21566.2.141.96/2866.2.141.97 to 66.2.141.11066.2.141.11114
21666.2.141.112/2866.2.141.113 to 66.2.141.12666.2.141.12714
21766.2.141.128/2866.2.141.129 to 66.2.141.14266.2.141.14314
21866.2.141.144/2866.2.141.145 to 66.2.141.15866.2.141.15914
21966.2.141.160/2866.2.141.161 to 66.2.141.17466.2.141.17514
22066.2.141.176/2866.2.141.177 to 66.2.141.19066.2.141.19114
22166.2.141.192/2866.2.141.193 to 66.2.141.20666.2.141.20714
22266.2.141.208/2866.2.141.209 to 66.2.141.22266.2.141.22314
22366.2.141.224/2866.2.141.225 to 66.2.141.23866.2.141.23914
22466.2.141.240/2866.2.141.241 to 66.2.141.25466.2.141.25514
22566.2.142.0/2866.2.142.1 to 66.2.142.1466.2.142.1514
22666.2.142.16/2866.2.142.17 to 66.2.142.3066.2.142.3114
22766.2.142.32/2866.2.142.33 to 66.2.142.4666.2.142.4714
22866.2.142.48/2866.2.142.49 to 66.2.142.6266.2.142.6314
22966.2.142.64/2866.2.142.65 to 66.2.142.7866.2.142.7914
23066.2.142.80/2866.2.142.81 to 66.2.142.9466.2.142.9514
23166.2.142.96/2866.2.142.97 to 66.2.142.11066.2.142.11114
23266.2.142.112/2866.2.142.113 to 66.2.142.12666.2.142.12714
23366.2.142.128/2866.2.142.129 to 66.2.142.14266.2.142.14314
23466.2.142.144/2866.2.142.145 to 66.2.142.15866.2.142.15914
23566.2.142.160/2866.2.142.161 to 66.2.142.17466.2.142.17514
23666.2.142.176/2866.2.142.177 to 66.2.142.19066.2.142.19114
23766.2.142.192/2866.2.142.193 to 66.2.142.20666.2.142.20714
23866.2.142.208/2866.2.142.209 to 66.2.142.22266.2.142.22314
23966.2.142.224/2866.2.142.225 to 66.2.142.23866.2.142.23914
24066.2.142.240/2866.2.142.241 to 66.2.142.25466.2.142.25514
24166.2.143.0/2866.2.143.1 to 66.2.143.1466.2.143.1514
24266.2.143.16/2866.2.143.17 to 66.2.143.3066.2.143.3114
24366.2.143.32/2866.2.143.33 to 66.2.143.4666.2.143.4714
24466.2.143.48/2866.2.143.49 to 66.2.143.6266.2.143.6314
24566.2.143.64/2866.2.143.65 to 66.2.143.7866.2.143.7914
24666.2.143.80/2866.2.143.81 to 66.2.143.9466.2.143.9514
24766.2.143.96/2866.2.143.97 to 66.2.143.11066.2.143.11114
24866.2.143.112/2866.2.143.113 to 66.2.143.12666.2.143.12714
24966.2.143.128/2866.2.143.129 to 66.2.143.14266.2.143.14314
25066.2.143.144/2866.2.143.145 to 66.2.143.15866.2.143.15914
25166.2.143.160/2866.2.143.161 to 66.2.143.17466.2.143.17514
25266.2.143.176/2866.2.143.177 to 66.2.143.19066.2.143.19114
25366.2.143.192/2866.2.143.193 to 66.2.143.20666.2.143.20714
25466.2.143.208/2866.2.143.209 to 66.2.143.22266.2.143.22314
25566.2.143.224/2866.2.143.225 to 66.2.143.23866.2.143.23914
25666.2.143.240/2866.2.143.241 to 66.2.143.25466.2.143.25514

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.