200-301 Question 169
Single answerA network administrator is configuring a switch with VLANs to segment traffic between different departments in the organization. After assigning the appropriate ports to VLANs and verifying connectivity, the administrator notices that devices in one VLAN cannot communicate with devices in another VLAN. What could be the most likely reason for this issue?
- A
The switch does not have inter-VLAN routing configured.
- B
The ports assigned to the VLANs are in access mode rather than trunk mode.
- C
The VLANs are not configured with the same VLAN ID on all switches.
- D
The spanning tree protocol (STP) is blocking the VLAN traffic.
Show answer and explanation
Correct answer: A
Explanation
In a VLAN configuration, devices within the same VLAN can communicate directly. However, for communication between different VLANs, inter-VLAN routing (usually configured on a Layer 3 device such as a router or Layer 3 switch) is necessary to enable traffic to pass between VLANs. Without inter-VLAN routing, VLANs remain isolated and cannot communicate.
- A. Correct.
Inter-VLAN routing is required for devices in different VLANs to communicate. Without it, VLANs remain isolated, which is likely the cause of the issue.
- B. Incorrect.
Access mode is used to assign ports to a single VLAN and does not affect inter-VLAN communication. Trunk mode is not necessary for communication within a single switch.
- C. Incorrect.
Having consistent VLAN IDs on all switches is important for multi-switch VLAN communication, but it does not explain the inability to communicate between VLANs on the same switch.
- D. Incorrect.
STP is used to prevent loops in the network and does not specifically block VLAN traffic unless there is a loop or misconfiguration.