“Perfect isolation,” Alex said, closing Packet Tracer. “Almost as good as my weekend plans.”
Alex learned the hard lesson: deleting a VLAN from one switch doesn’t delete it from others. But it does break connectivity for any access port still assigned to that missing VLAN on that switch.
“Allowed VLANs,” Alex muttered. “Add 30.”
Alex blinked. “Why would anyone—fine.” 3.3.12 packet tracer - vlan configuration.pka
Professor Lasky walked by, glanced at the screen, and said only: “Three VLANs today. Three hundred in the real world. The logic doesn’t change.”
Then step 8: “Delete VLAN 20 from S1.”
He walked off. The switches hummed.
But Alex made a classic mistake. On S2, Alex forgot to allow VLAN 30 on the trunk to S3. Suddenly, Staff PCs on S2 couldn’t talk to Staff PCs on S3.
interface fastEthernet 0/1 switchport mode access switchport access vlan 10 exit interface fastEthernet 0/2 switchport mode access switchport access vlan 20 F0/3 → VLAN 30. F0/4 → VLAN 10. And so on.
But Professor Lasky had hidden a trap. The instructions, step 7: “Verify that PC3 cannot ping PC5.” Alex did. It couldn’t. Good. “Perfect isolation,” Alex said, closing Packet Tracer
“Right,” Alex groaned. “The switch doesn’t know which PC belongs to which VLAN. It’s like a hotel front desk that doesn’t ask for your room key.” Back on S1:
Alex cracked knuckles. Time to build walls. On Switch S1 , Alex typed:
The scenario: VLAN Configuration . Objective: Slice this single broadcast domain into three separate pieces of virtual reality. “Allowed VLANs,” Alex muttered
The basement lab of Meridian Community College. Racks of aging but reliable Cisco switches hum in the corner. On a monitor, the Packet Tracer interface glows green.
“I need a trunk,” Alex whispered.