Gateoverflow

Question

https://gateoverflow.in/12913/company-granted-the-site-address-company-needs-1000-subnets

Can someone solve this question clearly.Also the division of subnet start from 0 or from 1 leaving 0 for Network Address.

Comments

As 1000 subnets needed so ceil[log(1000) ]= 10 , so u need 10 bits for this subneting 

now , Nid = 181.55.0.0 [ as its classfull so split 181 ---  10110101   as starting with 10 means this ip belongs to class B ]

we knw that class B ips are divided 16 Nid and 16 hid , so the first 16 bit of our adress is nid 

Now we have to borrow 10 bits from hid for subnetting

last subnet wil have 1000 in its subnet so [representation of 1000 = 1111101000]

a)   so adresss of last subnet  = 181.55.11111010.00000000   [last 6 bit is hid so for dba put 1 in hid part}

     thus , DBA of last subnet = 181.55.11111010.00111111 = 181.55.250.63]