Network – just to remenber

from here

IPv4 CIDR
Address
format
Difference
to last address
MaskAddressesRelative
to class
A, B, C
Restrictions

Typical use
Decimal2n
a.b.c.d/32+0.0.0.0255.255.255.2551201256 CHost route
a.b.c.d/31+0.0.0.1255.255.255.2542211128 Cd = 0 … (2n) … 254Point to point links (RFC 3021)
a.b.c.d/30+0.0.0.3255.255.255.252422164 Cd = 0 … (4n) … 252Point to point links (glue network)
a.b.c.d/29+0.0.0.7255.255.255.248823132 Cd = 0 … (8n) … 248Smallest multi-host network
a.b.c.d/28+0.0.0.15255.255.255.2401624116 Cd = 0 … (16n) … 240Small LAN
a.b.c.d/27+0.0.0.31255.255.255.2243225⅛ Cd = 0 … (32n) … 224
a.b.c.d/26+0.0.0.63255.255.255.1926426¼ Cd = 0, 64, 128, 192
a.b.c.d/25+0.0.0.127255.255.255.12812827½ Cd = 0, 128Large LAN
a.b.c.0/24+0.0.0.255255.255.255.0256281 C
a.b.c.0/23+0.0.1.255255.255.254.0512292 Cc = 0 … (2n) … 254
a.b.c.0/22+0.0.3.255255.255.252.01,0242104 Cc = 0 … (4n) … 252Small business
a.b.c.0/21+0.0.7.255255.255.248.02,0482118 Cc = 0 … (8n) … 248Small ISP/ large business
a.b.c.0/20+0.0.15.255255.255.240.04,09621216 Cc = 0 … (16n) … 240
a.b.c.0/19+0.0.31.255255.255.224.08,19221332 Cc = 0 … (32n) … 224ISP/ large business
a.b.c.0/18+0.0.63.255255.255.192.016,38421464 Cc = 0, 64, 128, 192
a.b.c.0/17+0.0.127.255255.255.128.032,768215128 Cc = 0, 128
a.b.0.0/16+0.0.255.255255.255.0.065,536216256 C = B
a.b.0.0/15+0.1.255.255255.254.0.0131,0722172 Bb = 0 … (2n) … 254
a.b.0.0/14+0.3.255.255255.252.0.0262,1442184 Bb = 0 … (4n) … 252
a.b.0.0/13+0.7.255.255255.248.0.0524,2882198 Bb = 0 … (8n) … 248
a.b.0.0/12+0.15.255.255255.240.0.01,048,57622016 Bb = 0 … (16n) … 240
a.b.0.0/11+0.31.255.255255.224.0.02,097,15222132 Bb = 0 … (32n) … 224
a.b.0.0/10+0.63.255.255255.192.0.04,194,30422264 Bb = 0, 64, 128, 192
a.b.0.0/9+0.127.255.255255.128.0.08,388,608223128 Bb = 0, 128
a.0.0.0/8+0.255.255.255255.0.0.016,777,216224256 B = ALargest IANA block allocation
a.0.0.0/7+1.255.255.255254.0.0.033,554,4322252 Aa = 0 … (2n) … 254
a.0.0.0/6+3.255.255.255252.0.0.067,108,8642264 Aa = 0 … (4n) … 252
a.0.0.0/5+7.255.255.255248.0.0.0134,217,7282278 Aa = 0 … (8n) … 248
a.0.0.0/4+15.255.255.255240.0.0.0268,435,45622816 Aa = 0 … (16n) … 240
a.0.0.0/3+31.255.255.255224.0.0.0536,870,91222932 Aa = 0 … (32n) … 224
a.0.0.0/2+63.255.255.255192.0.0.01,073,741,82423064 Aa = 0, 64, 128, 192
a.0.0.0/1+127.255.255.255128.0.0.02,147,483,648231128 Aa = 0, 128
0.0.0.0/0+255.255.255.2550.0.0.04,294,967,296232256 A

In common usage