An engineer is designing a network for a customer running a wireless network with a common VLAN for all APs. The customer is experiencing unicast flooding in the Layer 2 network between the aggregation and access layers. The customer wants to reduce the flooding and improve convergence time. Which solution meets these requirements?
Migrating to a Layer 3 access campus design, if the APs can run on separate VLANs, is the best solution to reduce unicast flooding and improve convergence time. Layer 3 designs significantly minimize Layer 2 broadcast domains by implementing routing at the access layer. This reduces the risk of unicast flooding caused by aging out entries in the CAM table. Furthermore, Layer 3 designs enhance the network's convergence time by eliminating the complexities associated with Spanning Tree Protocol.
I think B The default ARP table aging time is 4 hours while the CAM holds the entries for only 5 minutes. The switch sends out a frame to all forwarding ports within the respective VLAN when the destination MAC address is aged out from the CAM table. You need a CAM aging timer greater or equal to the ARP timeout in order to prevent unicast flooding. https://www.cisco.com/c/en/us/support/docs/switches/catalyst-6500-series-switches/71079-arp-cam-tableissues.html#:~:text=The%20default%20ARP%20table%20aging%20time%20is%204,ARP%20timeout%20in%20order%20to%20prevent%20unicast%20flooding.
But B says "reduce ARP timers to match CAM timers". The flooding will still happen at same interval.
L3 Access Layer design will eliminate STP along with providing better convergence times than traditional L2 design.
Answer is B
Spanning-tree protocol looping behavior, including blocked links, slow convergence, asymmetric forwarding, and switch CAM and ARP table tuning to address unicast flooding https://www.cisco.com/c/en/us/td/docs/solutions/CVD/Campus/cisco-campus-lan-wlan-design-guide.html
Answer B is correct based on explanations provided by Hope66