Number of IPs

Question

For Subnet Mask 255.255.255.192 & IP 200.1.2.3, the number of IP addresses wasted are __________.

Comments

is it 61 ??

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Answer was given as 8.

Answer 1

IP: 200.1.2.3 - Class C IP

255.255.255.192: SM = (N/w ID + Subnet ID = 1's  && Host ID = 0's)

11111111.11111111.11111111.11000000 - two subnet ID

So 2² = 4 subnets.

Each subnet will eat up 2 IPs ( 1 for N/w ID and 1 for Direct Broadcasting ).

So Answer is 4×2= 8

Comments

is that right? because all 0's subnet and 1's subnet will not be used for addressing , so we need to add all 0's subnet to the wasted address i think

see this section "Problems with Subnet Zero and the All-Ones Subnet"

http://www.cisco.com/c/en/us/support/docs/ip/dynamic-address-allocation-resolution/13711-40.html

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there will be four subnets:

00000000 - 00111111  (0-63) - we can't use first and last

01000000 - 01111111  (64-127)

10000000 - 10111111  (128-191)

11000000 - 11111111 (192-255)

Host's having all 0's will become subnet Id of that subnet.

We can't use Host's having all 1's. They will be used for DBA.