350-401 Question 131
Select 2A network administrator is troubleshooting an EtherChannel issue between two switches. The EtherChannel is configured dynamically using LACP, but the interfaces are not aggregating into the bundle. Upon reviewing the configuration, the administrator finds the following settings:
-
SwitchA:
interface range Gig1/0/1 - 2channel-group 1 mode activeswitchport mode trunk
-
SwitchB:
interface range Gig1/0/1 - 2channel-group 1 mode passiveswitchport mode access
Which configurations must the administrator correct to successfully form the EtherChannel?
- A
Change SwitchB's
switchport mode accesstoswitchport mode trunk. - B
Change SwitchA's
channel-group 1 mode activetochannel-group 1 mode on. - C
Change SwitchB's
channel-group 1 mode passivetochannel-group 1 mode active. - D
Ensure that both SwitchA and SwitchB interfaces are configured with the same allowed VLANs.
- E
Change SwitchA's
channel-group 1 mode activetochannel-group 1 mode passiveto match SwitchB.
Show answer and explanation
Correct answers: A, D
Explanation
For EtherChannel using LACP to form successfully, the interfaces on both switches must have matching configurations, including the same switchport mode (e.g., trunk or access) and allowed VLANs. Additionally, at least one side must be in 'active' mode to initiate the negotiation. In this scenario, correcting the mismatch in switchport modes (trunk vs. access) and ensuring the VLAN configurations match will resolve the issue.
- A. Correct.
Correct: EtherChannel requires both switches to use the same encapsulation type on the interfaces. Since SwitchA is configured as a trunk and SwitchB as an access port, this mismatch will prevent the bundle from forming.
- B. Incorrect.
Incorrect: The
onmode forces EtherChannel without negotiation protocols (LACP or PAgP). This mode bypasses the dynamic nature of LACP and would not solve the issue in this scenario. - C. Incorrect.
Incorrect: While setting SwitchB to
mode activewould work for LACP, the EtherChannel would still fail without resolving the trunk/access mismatch. - D. Correct.
Correct: Both ends of an EtherChannel must have matching VLAN configurations. If the allowed VLANs differ, the EtherChannel will not form properly.
- E. Incorrect.
Incorrect: Configuring both sides to
mode passivewill prevent EtherChannel from forming, as neither side will initiate LACP negotiation.