N10-009 Question 154
Single answerVirtual Local Area Network (VLAN), VLAN database, Switch virtual interface (SVI)A network administrator creates VLAN 20 for the accounting department on a Layer 2 switch and assigns several access ports to that VLAN. The administrator also wants to manage the switch remotely from a workstation in VLAN 20. After creating interface vlan 20 and assigning it the IP address 192.168.20.2/24, the administrator still cannot ping the SVI from a host in VLAN 20. The host can ping other devices in the same VLAN. Which action is MOST likely required to make the SVI reachable?
- A
Configure at least one active switch port in VLAN 20 so the SVI can come up
- B
Set the SVI IP address as the default gateway for all VLAN 20 hosts
- C
Add VLAN 20 to the switch's VLAN database with a VTP server
- D
Enable routing on the switch so the SVI can answer ICMP requests
Show answer and explanation
Correct answer: A
Explanation
This question tests practical understanding of VLANs, the VLAN database, and switch virtual interfaces (SVIs). On a Layer 2 switch, an SVI is commonly used for management access. For the SVI to be operational, the VLAN must exist in the VLAN database and generally must have at least one active member port in an up/up state. If the VLAN exists but has no active ports, the SVI often remains down and cannot be reached. The fact that hosts in VLAN 20 can already communicate with each other confirms the VLAN is present and functioning at Layer 2, making VTP or VLAN creation issues unlikely. Also, a default gateway is not necessary for same-subnet communication, and IP routing is only needed for communication between VLANs. These behaviors align with common switch operating principles documented by major vendors such as Cisco in their guidance for VLANs and SVIs.
- A. Correct.
Correct. On most switches, an SVI remains down/down or administratively up but line protocol down until the corresponding VLAN exists and has at least one active port in that VLAN in an up state. Since the VLAN was already created and hosts in VLAN 20 can communicate with each other, the likely issue is that no active port is currently bringing VLAN 20 into an operational state for the SVI. This is a common requirement for management SVIs on Layer 2 switches.
- B. Incorrect.
Incorrect. A host does not need to use the SVI as its default gateway just to ping the SVI when both are in the same subnet and VLAN. Default gateway configuration is only needed when traffic must leave the local subnet. This option reflects a common misconception between local Layer 2 reachability and routed traffic.
- C. Incorrect.
Incorrect. The scenario already states that VLAN 20 was created and hosts in VLAN 20 can reach each other, which means the VLAN exists in the switch's VLAN database and is functioning locally. A VTP server is not required for a single switch to use a VLAN, and modern best practice is often to use transparent mode or manual VLAN creation unless VTP is specifically needed.
- D. Incorrect.
Incorrect. Enabling routing is not required for a Layer 2 switch to respond to traffic sent directly to an SVI in the same subnet. IP routing is needed for inter-VLAN routing, not for basic management access to the switch from a host in the same VLAN. This distractor targets the common confusion between SVI-based management and multilayer routing.