[Solved] Identify the error in this subnet mask: 255.255.255.250 — Ans: Subnet masks must have continuous ones; 250 is invalid | Computer Networks

Computer Networks - IP Addressing

Identify the error in this subnet mask: 255.255.255.250

ASubnet masks must have continuous ones; 250 is invalid

BSubnet masks cannot have 255 in any octet

CSubnet masks must be exactly 4 octets of zeros

DSubnet masks must always end with 128

Step-by-Step Solution

Solution:

Step 1: Understand valid subnet mask rules
Subnet masks must have continuous ones from left to right in binary.
Step 2: Check binary of 250
250 in binary is 11111010, which breaks continuity (has zero between ones).
Final Answer:
Subnet masks must have continuous ones; 250 is invalid -> Option A
Quick Check:
Subnet mask continuity = must be continuous ones [OK]

Quick Trick: Subnet mask bits must be continuous ones [OK]

Common Mistakes:

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Identify the error in this subnet mask: 255.255.255.250