350-401 · Question #634
Refer to the exhibit. An engineer must set up connectivity between a campus aggregation layer and a branch office access layer. The engineer uses dynamic trunking protocol to establish this connection
The correct answer is C. Configure the correct native VLAN on the remote interface. The issue describes a problem with management traffic on VLAN1 not passing over a DTP-established trunk link, which points to a native VLAN mismatch or a related trunking configuration problem.
Question
Exhibits
Options
- AAllow all VLANs on the trunk links
- BDisable Spanning Tree for the native VLAN.
- CConfigure the correct native VLAN on the remote interface
- DChange both interfaces to access ports.
How the community answered
(27 responses)- A4% (1)
- B11% (3)
- C67% (18)
- D19% (5)
Why each option
The issue describes a problem with management traffic on VLAN1 not passing over a DTP-established trunk link, which points to a native VLAN mismatch or a related trunking configuration problem.
Allowing all VLANs on the trunk links is generally good practice but does not directly resolve a native VLAN mismatch problem, as the issue specifically pertains to how untagged frames for the native VLAN are handled.
Disabling Spanning Tree Protocol (STP) for the native VLAN (VLAN1) is extremely dangerous as it can create Layer 2 loops and is not related to frames not passing due to native VLAN mismatch.
When trunk links have mismatched native VLANs, frames for the native VLAN are untagged on one side but expected as tagged or untagged on the other, leading to dropped frames for that VLAN. Configuring the correct (matching) native VLAN on both ends of the trunk link ensures that untagged frames from the native VLAN are correctly processed, resolving the communication issue for VLAN1.
Changing both interfaces to access ports would disable trunking, preventing communication for multiple VLANs and thus not resolving the issue of management traffic needing to pass over a trunk link.
Concept tested: Trunking native VLAN mismatch
Source: https://www.cisco.com/c/en/us/support/docs/lan-switching/ethernet-best-practices/100063-6.html
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