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300-420 · Question #200

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…

The correct answer is B. Align HSRP primary and STP root bridges and reduce ARP timers to match CAM timers on the. 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…

Advanced Enterprise Campus Networks

Question

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?

Options

  • AMigrate all APs to a common Layer 2 access layer switch and run Layer 3 from the aggregation
  • BAlign HSRP primary and STP root bridges and reduce ARP timers to match CAM timers on the
  • CMigrate to a Layer 3 access campus design if the APs can run on separate VLANs.
  • DAlign HSRP primary and STP root bridges if the APs cannot run on separate VLANs.

How the community answered

(60 responses)
  • A
    25% (15)
  • B
    57% (34)
  • C
    7% (4)
  • D
    12% (7)

Explanation

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. tableissues.html#:~:text=The%20default%20ARP%20table%20aging%20time%20is%204,ARP% 20timeout%20in%20order%20to%20prevent%20unicast%20flooding.

Topics

#Unicast Flooding Mitigation#Layer 2/3 Convergence#HSRP/STP Optimization#ARP/CAM Timers

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