400-007 · Question #8
Company XYZ needs advice in redesigning their legacy Layer 2 infrastructure. Which technology should be included in the design to minimize or avoid convergence delays due to STP or FHRP and provide…
The correct answer is B. Use switch clustering in the core/distribution layer. Switch clustering at the core and distribution layer merges physical switches into a single logical device, eliminating STP blocked ports and FHRP failover requirements for a loop-free topology.
Question
Company XYZ needs advice in redesigning their legacy Layer 2 infrastructure. Which technology should be included in the design to minimize or avoid convergence delays due to STP or FHRP and provide a loop-free topology?
Options
- AUse switch clustering in the access layer.
- BUse switch clustering in the core/distribution layer.
- CUse spanning-tree PortFast.
- DUse BFD.
How the community answered
(20 responses)- A20% (4)
- B70% (14)
- C5% (1)
- D5% (1)
Why each option
Switch clustering at the core and distribution layer merges physical switches into a single logical device, eliminating STP blocked ports and FHRP failover requirements for a loop-free topology.
Clustering at the access layer does not remove STP or FHRP between the access and distribution tiers, leaving convergence delays unresolved in the most impactful part of the network.
Technologies such as Cisco VSS or StackWise at the core and distribution layer present multiple physical switches as one logical forwarding entity, meaning no Layer 2 loops can form between them and STP blocking is unnecessary. Because the cluster appears as a single device, only one default gateway address exists, removing the need for HSRP or VRRP and their associated failover timers. This design achieves both a loop-free topology and the elimination of STP and FHRP convergence delays simultaneously.
PortFast only speeds up edge port transitions from blocking to forwarding and does not eliminate STP from the overall network design or address FHRP failover delays.
BFD accelerates failure detection for routing protocols but does not remove the underlying STP topology recalculation process or FHRP switchover delays.
Concept tested: Switch clustering to eliminate STP and FHRP convergence delays
Source: https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst6500/ios/12-2SX/configuration/guide/book/vss.html
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