CompTIA Network+ (N10-009)Network ImplementationMedium
A network administrator is configuring a new Layer 3 switch to route traffic between VLANs 10, 20, and 30. The switch has a single physical interface connected to a router for external network access. Which of the following configuration elements is required on the Layer 3 switch to enable inter-VLAN routing?
- ACreate Switched Virtual Interfaces (SVIs) for each VLAN.
- BConfigure the physical interface as an access port for each VLAN.
- CEnable STP PortFast on all VLAN interfaces.
- DSet up a static route for each VLAN to the external router.
Show answer & explanationAnswer & explanation
Correct answer: A. Create Switched Virtual Interfaces (SVIs) for each VLAN.
To enable inter-VLAN routing on a Layer 3 switch, a Switched Virtual Interface (SVI), also known as a VLAN interface, must be created for each VLAN. The SVI acts as the default gateway for devices in that VLAN.
Why the other options are wrong
- B. Physical interfaces connected to end devices are typically access ports, but the question asks about routing between VLANs, which requires a Layer 3 interface.
- C. STP PortFast is used to bring edge ports to a forwarding state immediately, preventing STP delays, but it's not directly related to enabling inter-VLAN routing.
- D. While a default route to the external router is needed for outside access, routing between the VLANs on the switch itself is handled by the SVIs, not by static routes to an external device for internal VLAN communication.
Switched Virtual Interface (SVI)
A logical Layer 3 interface on a Layer 3 switch that is associated with a VLAN. It allows the switch to perform Layer 3 routing functions for traffic originating from or destined to that VLAN.
- Acts as the default gateway for devices within its associated VLAN.
- Requires an IP address and subnet mask.
- Enables inter-VLAN routing without needing an external router for internal VLAN traffic.
Memory trick: Think of an SVI as a 'virtual router port' for each VLAN, allowing them to talk.