subnet woes.

hexem

Ok so iv'e checked out the easy subnetting guide on here, seem's pretty easy to follow but when it come's to class a/b addresses, i get confused slightly.

take this for example.

105.254.219.251/15

Ok so following the guide,

16 - 15 = 2 ^ 1 = 2 (block size?)

Addresses like this confuse me..

miller811

hexem wrote: »

Ok so iv'e checked out the easy subnetting guide on here, seem's pretty easy to follow but when it come's to class a/b addresses, i get confused slightly.

take this for example.

105.254.219.251/15

Ok so following the guide,

16 - 15 = 2 ^ 1 = 2 (block size?)

Addresses like this confuse me..

always use the following

There are 3 main classes of IP address that we are concerned with.

Class A Range 0 - 127 in the first octet (0 and 127 are reserved)
Class B Range 128 - 191 in the first octet
Class C Range 192 - 223 in the first octet

Below shows you how, for each class, the address is split in terms of network (N) and host (H) portions.

NNNNNNNN . HHHHHHHH . HHHHHHHH . HHHHHHHH Class A
NNNNNNNN . NNNNNNNN . HHHHHHHH . HHHHHHHH Class B
NNNNNNNN . NNNNNNNN . NNNNNNNN . HHHHHHHH Class C


so it is a class A address

105.254.219.251/15

7 bits are being borrowed so it is a 2 bit range, as you stated

subnet 105.254.0.0
first host 105.254.0.1
last host 105.255.255.254
broadcast 105.255.255.255

17 bits are used for the host addresses = 131072 (-2) hosts

practice here
IP Subnet Practice