The default port between S1 and S2 (Gig0/1) was just a regular port. It saw a ping from PC1 (VLAN 10, S1) and dropped it before it reached S2.
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. 3.3.12 packet tracer - vlan configuration.pka
interface gigabitEthernet 0/1 switchport mode trunk switchport trunk allowed vlan 10,20,30 Same on S2’s G0/1 and S3’s G0/2. The default port between S1 and S2 (Gig0/1)
“Wait,” Alex frowned. “That’s good. But why can’t PC1 ping PC3?” 3.3.12 packet tracer - vlan configuration.pka
The Switch that Forgot How to Listen
Professor Lasky’s note floated at the top of the instructions: “VLANs don’t just happen. You build walls where there are none.”