subnet woes.

hexemhexem Posts: 177Member
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..
ICND1 - Passed 25/01/10
ICND2 - Passed 9/03/10

Studying CCNA:S

Comments

  • miller811miller811 Posts: 897Member
    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
    I don't claim to be an expert, but I sure would like to become one someday.

    Quest for 11K pages read in 2011
    Page Count total to date - 1283
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