Implementing and Operating Cisco Enterprise Network Core Technologies (ENCOR) v1.2InfrastructureMedium
A network engineer is troubleshooting a connection between two Catalyst 9300 switches that are configured for an EtherChannel. The EtherChannel is not forming, and both ends are configured to actively negotiate the bundle. After checking the physical connections, the engineer suspects a mismatch in the bundling protocol. Which protocol should be configured on both switches for active negotiation?
- ACDP
- BPAGP
- CVTP
- DLACP
Show answer & explanationAnswer & explanation
Correct answer: D. LACP
Link Aggregation Control Protocol (LACP) is an open standard protocol used for actively negotiating and forming EtherChannel bundles. When both switches are configured for 'active' mode, they actively send LACP PDUs to discover and agree upon forming the EtherChannel.
Why the other options are wrong
- A. CDP (Cisco Discovery Protocol) is used for discovering neighboring Cisco devices, not for EtherChannel negotiation.
- B. PAGP (Port Aggregation Protocol) is a Cisco proprietary protocol for EtherChannel negotiation.
- C. VTP (VLAN Trunking Protocol) is used for managing VLANs across a switched network, not EtherChannels.
Link Aggregation Control Protocol (LACP)
An open standard protocol that allows network devices to dynamically bundle multiple physical links into a single logical channel (EtherChannel) for increased bandwidth and redundancy.
- Open standard protocol (IEEE 802.3ad).
- Supports active and passive negotiation modes.
- Dynamically forms EtherChannels.
- Provides link redundancy and load balancing.
Memory trick: LACP: The standard way to link up.