IP adresser

Class 1st Octet Decimal Range 1st Octet High Order Bits Network/Host ID (N=Network, H=Host) Default Subnet Mask Number of Networks Hosts per Network (Usable Addresses)
A 1 – 126* 0 N.H.H.H 255.0.0.0 126 (27 – 2) 16,777,214 (224 – 2)
B 128 – 191 10 N.N.H.H 255.255.0.0 16,382 (214 – 2) 65,534 (216 – 2)
C 192 – 223 110 N.N.N.H 255.255.255.0 2,097,150 (221 – 2) 254 (28 – 2)
D 224 – 239 1110 Reserved for Multicasting
E 240 – 254 1111 Experimental; used for research

Note: Class A addresses 127.0.0.0 to 127.255.255.255 cannot be used and is reserved for loopback and diagnostic functions.

Private IP Addresses

Class Private Networks Subnet Mask Address Range
A 10.0.0.0 255.0.0.0 10.0.0.0 – 10.255.255.255
B 172.16.0.0 255.240.0.0 172.16.0.0 – 172.31.255.255
C 192.168.0.0 255.255.0.0 192.168.0.0 – 192.168.255.255
Note: 
There is another range of IP addresses  reserved for private networks:-
Type Private Networks Subnet Mask Address Range
APIPA 169.254.0.0 255.255.0.0 169.254.0.0 – 169.254.255.255
Test 192.0.2.0 255.255.255.0 192.0.2.0 – 192.0.2.255
APIPA range (Ah-peep-ah) – Automatic Private IP Addressing.
Microsoft has incorporated this into all versions of Windows.
The APIPA system gives nothing but trouble!