Cisco CCNA (200-301)Network AccessMedium
A network technician is configuring an EtherChannel using LACP between two Cisco Catalyst 2960 switches. On SW1, the interfaces Gi0/1 and Gi0/2 are configured with 'channel-group 1 mode active'. On SW2, the interfaces Gi0/1 and Gi0/2 are configured with 'channel-group 1 mode passive'. What is the operational status of the EtherChannel?
- AThe EtherChannel will form successfully.
- BThe EtherChannel will not form because both sides must be 'active'.
- CThe EtherChannel will not form because both sides must be 'passive'.
- DThe EtherChannel will form, but only for traffic from SW1 to SW2.
Show answer & explanationAnswer & explanation
Correct answer: A. The EtherChannel will form successfully.
LACP 'active' mode initiates LACP negotiations and sends LACP PDUs. LACP 'passive' mode responds to LACP PDUs but does not initiate them. When 'active' connects to 'passive', the active side initiates, and the passive side responds, successfully forming an EtherChannel.
Why the other options are wrong
- B. This statement is incorrect; active/passive is a valid combination.
- C. This statement is incorrect; passive/passive will not form an EtherChannel.
- D. EtherChannel is bidirectional; if it forms, it carries traffic in both directions.
LACP Active/Passive Interaction
An EtherChannel using LACP will form successfully when one side is configured in 'active' mode and the other in 'passive' mode, as 'active' initiates negotiations and 'passive' responds.
- LACP Active: Actively sends LACP PDUs and tries to negotiate an EtherChannel.
- LACP Passive: Responds to LACP PDUs but does not initiate them.
- A successful LACP EtherChannel requires at least one side to be in 'active' mode.
Memory trick: Active Asks, Passive Partners: Channel Connects.