3 Ethernet Switching and VLANs Free Online FlashCards

How does a switch learn which port leads to a MAC address?

A switch learns the source MAC address of each frame and associates it with a VLAN and port in its forwarding table.

What does a switch do with a frame whose destination MAC address is unknown?

It floods the frame to ports within the same VLAN, excluding the port on which it arrived.

What does a VLAN define on a switched network?

A VLAN is a logical Layer 2 network that creates a separate broadcast domain.

What is needed for communication between different VLANs?

Devices in different VLANs need a router or Layer 3 switch to communicate; VLANs alone do not provide inter-VLAN routing.

What traffic does an access port carry?

An access port carries one data VLAN and normally sends and receives untagged frames.

How does a trunk distinguish traffic from multiple VLANs?

A trunk carries multiple VLANs, usually identifying frames with IEEE 802.1Q tags. Native VLAN traffic is typically untagged.

Which VLAN settings should match at both ends of a trunk?

Both ends must agree on the native VLAN and allowed VLANs for the trunk.

What is a good practice for a trunk’s allowed VLAN list?

Allow only the VLANs required on each trunk instead of relying on a broad default.

How does STP prevent loops while retaining redundancy?

STP prevents Layer 2 loops by placing redundant paths into a non-forwarding state while preserving an alternate path.

What roles do the root bridge and alternate paths play in STP?

STP exchanges BPDUs and elects a root bridge; redundant paths can be blocked, and an alternate path can activate if an active path fails.

Where should PortFast be enabled?

Enable PortFast only on ports connected to end devices; it lets an edge port reach forwarding promptly.

What does BPDU Guard do when an edge port receives a BPDU?

BPDU Guard shuts an edge port if it receives a BPDU, helping protect the spanning-tree topology from an unexpected bridge or switch.