Courseiva
CCNA lab 18

Troubleshooting: a broken trunk between two switches

PCs in the same VLAN on two switches cannot talk. Find the trunk, native VLAN, allowed-list and VLAN database faults, and fix them.

About 25 minutes 6 devices 4 tasksAdvanced

Scenario

SW1 and SW2 should share VLAN 10 (SALES) and VLAN 20 (HR) over one trunk on Gi0/1, using VLAN 99 as the native VLAN as company policy requires. Neither VLAN works across the switches. Several faults are hiding in the two configurations. Use `show interfaces trunk`, `show interfaces g0/1 switchport`, `show vlan brief` and the running configs to find them. The trunk should allow exactly VLANs 10, 20 and 99.

Gi0/1Gi0/1Fa0/1eth0Fa0/2eth0Fa0/1eth0Fa0/2eth0SW1SW1 — Switch (Catalyst 2960-24)SW2SW2 — Switch (Catalyst 2960-24)PC1PC1 — PCPC2PC2 — PCPC3PC3 — PCPC4PC4 — PC

Your tasks

  1. Gi0/1 is trunking on both switches with native VLAN 99.
  2. Both ends allow exactly VLANs 10, 20 and 99.
  3. PC1 can ping PC3 (VLAN 10).
  4. PC2 can ping PC4 (VLAN 20).

The lab checks the result, not the exact commands. For example, a ping task passes only when the ping really succeeds through the network you built.

Start the lab