Cisco Certified Network Associate (CCNA) 200-301 — Question 854

Refer to the exhibit. VLAN 23 is being implemented between SW1 and SW2. The command show interface ethernet0/0 switchport has been issued on SW1. Ethernet0/0 on SW1 is the uplink to SW2. Which command when entered on the uplink interface allows PC 1 and PC 2 to communicate without impact to the communication between PC 11 and PC 12?