An administrator enables Layer 2 mode on a Citrix ADC SDX with multiple interfaces. Interfaces repeatedly go up and down while forwarding traffic. What action should be taken to stabilize forwarding?

• A. Disable Layer 2 mode on the Citrix ADC instance.
• B. Enable tagging on all interfaces.
• C. Enable Layer 3 mode along with Layer 2 mode.
• D. Enable MAC-based forwarding mode.

Answer: (B)

In Layer 2 mode, the SDX acts like a switch that forwards traffic across multiple interfaces, so frames must carry a VLAN context to keep traffic properly separated. If tagging isn’t enabled on all interfaces, frames from different tenants or networks can collide in the same broadcast domain, causing the switch-like forwarding state to churn as MAC addresses and VLANs are learned and relearned. Enabling tagging on every interface provides a consistent VLAN identifier for each frame, so the device can map traffic to the correct bridge domain and forward it only within the intended VLAN. This consistent VLAN tagging prevents misrouting and flooding, stabilizing forwarding across the interfaces.

Other options don’t address the underlying cause: turning off Layer 2 would remove the switching behavior but isn’t necessary here; layering in Layer 3 would change the mode of operation; MAC-based forwarding changes the forwarding decision mechanism but still relies on VLAN context for correct isolation, which tagging supplies.