| Netmask | Binary Netmask | CIDR | Notes |
|---|---|---|---|
255.255.255.255 |
11111111.11111111.11111111.11111111 |
/32 |
Specific Host |
255.255.255.254 |
11111111.11111111.11111111.11111110 |
/31 |
Unuseable |
255.255.255.252 |
11111111.11111111.11111111.11111100 |
/30 |
2 useable |
255.255.255.248 |
11111111.11111111.11111111.11111000 |
/29 |
6 useable |
255.255.255.240 |
11111111.11111111.11111111.11110000 |
/28 |
14 useable |
255.255.255.224 |
11111111.11111111.11111111.11100000 |
/27 |
30 useable |
255.255.255.192 |
11111111.11111111.11111111.11000000 |
/26 |
62 useable |
255.255.255.128 |
11111111.11111111.11111111.10000000 |
/25 |
126 useable |
255.255.255.0 |
11111111.11111111.11111111.00000000 |
/24 |
Class C, 254 useable |
255.255.254.0 |
11111111.11111111.11111110.00000000 |
/23 |
2 Class C’s |
255.255.252.0 |
11111111.11111111.11111100.00000000 |
/22 |
4 Class C’s |
255.255.248.0 |
11111111.11111111.11111000.00000000 |
/21 |
8 Class C’s |
255.255.240.0 |
11111111.11111111.11110000.00000000 |
/20 |
16 Class C’s |
255.255.224.0 |
11111111.11111111.11100000.00000000 |
/19 |
32 Class C’s |
255.255.192.0 |
11111111.11111111.11000000.00000000 |
/18 |
64 Class C’s |
255.255.128.0 |
11111111.11111111.10000000.00000000 |
/17 |
128 Class C’s |
255.255.0.0 |
11111111.11111111.00000000.00000000 |
/16 |
Class B |
255.254.0.0 |
11111111.11111110.00000000.00000000 |
/15 |
2 Class B’s |
255.252.0.0 |
11111111.11111100.00000000.00000000 |
/14 |
4 Class B’s |
255.248.0.0 |
11111111.11111000.00000000.00000000 |
/13 |
8 Class B’s |
255.240.0.0 |
11111111.11110000.00000000.00000000 |
/12 |
16 Class B’s |
255.224.0.0 |
11111111.11100000.00000000.00000000 |
/11 |
32 Class B’s |
255.192.0.0 |
11111111.11000000.00000000.00000000 |
/10 |
64 Class B’s |
255.128.0.0 |
11111111.10000000.00000000.00000000 |
/9 |
128 Class B’s |
255.0.0.0 |
11111111.00000000.00000000.00000000 |
/8 |
Class A |
254.0.0.0 |
11111110.00000000.00000000.00000000 |
/7 |
|
252.0.0.0 |
11111100.00000000.00000000.00000000 |
/6 |
|
248.0.0.0 |
11111000.00000000.00000000.00000000 |
/5 |
|
240.0.0.0 |
11110000.00000000.00000000.00000000 |
/4 |
|
224.0.0.0 |
11100000.00000000.00000000.00000000 |
/3 |
|
192.0.0.0 |
11000000.00000000.00000000.00000000 |
/2 |
|
128.0.0.0 |
10000000.00000000.00000000.00000000 |
/1 |
|
0.0.0.0 |
00000000.00000000.00000000.00000000 |
/0 |
Entire IP space |
RFC1918 name |
IP address range |
number of addresses |
classful description |
largest CIDR block (subnet mask) |
host id size |
24-bit block |
10.0.0.0 - 10.255.255.255 |
16,777,216 |
single class A |
10.0.0.0/8 (255.0.0.0) |
24 bits |
20-bit block |
172.16.0.0 - 172.31.255.255 |
1,048,576 |
16 contiguous class Bs |
172.16.0.0/12 (255.240.0.0) |
20 bits |
16-bit block |
192.168.0.0 - 192.168.255.255 |
65,536 |
256 contiguous class Cs |
192.168.0.0/16 (255.255.0.0) |
16 bits |
169.254.0.0/24 |
169.254.0.0 - 169.254.0.255 |
256 |
Reserved |
169.254.0.0/16 |
169.254.1.0 - 169.254.254.255 |
65,536 |
APIPA Range |
169.254.255.0/24 |
169.254.255.0 - 169.254.255.255 |
256 |
Reserved |
Link-local addressing details. More details in RFC3927.
224.0.0.0 - 224.0.0.255 |
(/24) Local Network Control Block |
224.0.0.0 |
base-address.mcast.net |
224.0.0.1 |
all-systems.mcast.net |
224.0.0.2 |
all-routers.mcast.net |
224.0.0.4 |
dvmrp.mcast.net |
224.0.0.22 |
igmp.mcast.net |
224.0.1.0 - 224.0.1.255 |
(/24) Internetwork Control Block |
224.0.1.1 |
ntp.mcast.net |
224.0.1.75 |
sip.mcast.net |
224.0.2.0 - 224.0.255.255 |
(65024) AD-HOC Block I |
224.1.0.0 - 224.1.255.255 |
(/16) RESERVED |
224.3.0.0 - 224.4.255.255 |
(2 /16s) AD-HOC Block II |
224.5.0.0 - 224.255.255.255 |
(251 /16s) RESERVED |
225.0.0.0 - 231.255.255.255 |
(7 /8s) RESERVED |
232.0.0.0 - 232.255.255.255 |
(/8) Source-Specific Multicast Block |
233.0.0.0 - 233.251.255.255 |
(16515072) GLOP Block |
233.252.0.0 - 233.255.255.255 |
(/14) AD-HOC Block III |
234.0.0.0 - 238.255.255.255 |
(5 /8s) RESERVED |
239.0.0.0 - 239.255.255.255 |
(/8) Administratively Scoped Block |
More detailed list. Serious details at RFC5771.
Special Use IPv4 Addresses
A good summary of interesting reserved ranges found in RFC 5735.
Address Block |
Present Use |
Reference |
0.0.0.0/8 |
"This" Network |
RFC 1122, Section 3.2.1.3 |
10.0.0.0/8 |
Private-Use Networks |
RFC 1918 |
127.0.0.0/8 |
Loopback |
RFC 1122, Section 3.2.1.3 |
169.254.0.0/16 |
Link Local |
RFC 3927 |
172.16.0.0/12 |
Private-Use Networks |
RFC 1918 |
192.0.0.0/24 |
IETF Protocol Assignments |
RFC 5736 |
192.0.2.0/24 |
TEST-NET-1 |
RFC 5737 |
192.88.99.0/24 |
6to4 Relay Anycast |
RFC 3068 |
192.168.0.0/16 |
Private-Use Networks |
RFC 1918 |
198.18.0.0/15 |
Network Interconnect, Device Benchmark Testing |
RFC 2544 |
198.51.100.0/24 |
TEST-NET-2 |
RFC 5737 |
203.0.113.0/24 |
TEST-NET-3 |
RFC 5737 |
224.0.0.0/4 |
Multicast |
RFC 3171 |
240.0.0.0/4 |
Reserved for Future Use |
RFC 1112, Section 4 |
255.255.255.255/32 |
Limited Broadcast |
RFC 919, Section 7, RFC 922, Section 7 |
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