DRDO CSE 2022 Paper 2 | Question: 20

Question

An organization is granted the $\text{IPv4}$ address block $130.56.0.0/16.$ The network administrator wants to create $1024$ subnets. Find the first and last addresses in the third subnet.

Comments

130.56.128/ 26

130.56. 191/ 26

Answer 1

$130.56.0.0/16$

NID = 16 bits , HID = 16 bits

so to divide into 1024 subnets we borrow 10 bits from HID

hence Subnet ID bits = 10(bold ones) , New HID = 6 bits

$130.56.\mathbf{00000000.00}000000/26$

First address of Subnet 3 = SID of Subnet 3 = $130.56.\mathbf{00000000.10}000000/26 = 130.56.0.128/26$

Last address of Subnet 3 = DBA of Subnet 3 = $130.56.\mathbf{00000000.10}111111/26 = 130.56.0.191/26$

Comments

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

It is useful to preserve and extend the interpretation of these special (network and broadcast) addresses in subnetted networks. This means the values of all zeros and all ones in the subnet field should not be assigned to actual (physical) subnets.

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Totally agreeing with you bro..but the thing you are talking about is the old convention

https://gateoverflow.in/1265/gate-cse-2007-question-67-isro2016-72

read the best answer in this question

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what if they ask subnet 1 or subnet 2 then what will be ans ? @thehitchh1ker @Shubhodeep