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Lakshman Patel RJIT
asked
in Computer Networks
Jan 5, 2019
edited
Apr 19, 2022
by Lakshman Patel RJIT

478 views
1 vote

CIDR general notation format:$a.b.c.d/n$ where n is the number of bits that are presented in network id.

- NID+SID= n bits
- HID=(32-n) bits

Subnet mask: it is $32$ bit number in which the number of 1’s indicates network id and subnet id, number of 0’s indicates host id part.

- NID+SID=all 1’s
- HID=all 0’s

Given IP address is $172.26.17.1/25$, here /25 represents the first 25 bits are all 1’s. that is

$172.26.17.1$ can be represented in binary form:

$11111111.11111111.11111111.10000000$, last $7$ 0’s represented as HID.

Therefore SM would be: $255.255.255.128$

So option $(D)$ is correct.

Ref:CIDR