300-320 · Question #388
When designing layer 2 STP based LAN with FHRP, what design recommendation should be followed?
The correct answer is A. Assign STP root with active FHRP device. The STP root bridge and the active FHRP gateway (e.g., HSRP active or VRRP master) should always reside on the same physical switch. If they are on different devices, end-host traffic destined for the default gateway must first traverse STP topology toward the FHRP active…
Question
When designing layer 2 STP based LAN with FHRP, what design recommendation should be followed?
Options
- AAssign STP root with active FHRP device
- BAssign native VLAN to lowest number in use
- CAvoid configuring router preempt
- DAvoid modifying STP & FHRP default timers
How the community answered
(23 responses)- A83% (19)
- B4% (1)
- C4% (1)
- D9% (2)
Explanation
The STP root bridge and the active FHRP gateway (e.g., HSRP active or VRRP master) should always reside on the same physical switch. If they are on different devices, end-host traffic destined for the default gateway must first traverse STP topology toward the FHRP active device, while STP's own topology is optimized toward a different root-creating suboptimal, asymmetric traffic paths and potentially hairpinning traffic unnecessarily. Aligning the STP root with the active FHRP device ensures that the traffic flows follow the most efficient path through the network. Preempt is generally recommended for FHRP to restore the primary device; native VLANs and timer modifications are separate concerns not directly related to this alignment principle.
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