Implementing and Operating Cisco Enterprise Network Core Technologies (ENCOR) v1.2InfrastructureMedium
A network engineer is designing a highly available data center network. The design requires that critical servers have their network interfaces connected to two different switches, and these interfaces operate as a single logical link for increased bandwidth and redundancy. If one physical link or switch fails, traffic should automatically reroute over the remaining active link without interruption. Which Layer 2 technology should be used to achieve this?
- ACisco Discovery Protocol (CDP)
- BVLAN Trunking Protocol (VTP)
- CSpanning Tree Protocol (STP)
- DLink Aggregation Control Protocol (LACP)
Show answer & explanationAnswer & explanation
Correct answer: D. Link Aggregation Control Protocol (LACP)
LACP (Link Aggregation Control Protocol) is used to bundle multiple physical links into a single logical link, providing increased bandwidth and redundancy. If one link fails, the remaining links continue to carry traffic, ensuring uninterrupted service. This is ideal for connecting critical servers to switches.
Why the other options are wrong
- A. CDP is used for discovering directly connected Cisco devices, not for link aggregation.
- B. VTP is used to manage VLAN configurations across switches, not for link redundancy/aggregation.
- C. STP prevents Layer 2 loops by blocking redundant paths, but LACP actively aggregates paths for both bandwidth and redundancy.
Link Aggregation Control Protocol (LACP)
An open-standard protocol (IEEE 802.3ad) that allows multiple physical Ethernet links to be bundled together to form a single logical channel, providing increased bandwidth and redundancy.
- Also known as EtherChannel (Cisco proprietary) or Port Channel.
- Provides load balancing across aggregated links.
- Ensures high availability; if one link fails, traffic is rerouted over others.
Memory trick: Links Unite for Strength and Safety.