The issue is that VLAN 10 has propagated to SW3, which is against the company policy. The company policy allows only VLAN 10 on SW1 and SW2. To correct this issue, the allowed VLANs on the trunk link connecting to SW3 should be configured to exclude VLAN 10. Option C accomplishes this by configuring the trunk link on SW2 (int gi1/2) to allow all VLANs except VLAN 10 (switchport trunk allowed vlan 1-9,11-4094). References: * Implementing and Operating Cisco Service Provider Network Core Technologies * On-Demand E-Learning