2 Switching, VLANs, and Wireless Networks Free Online FlashCards

What does a Layer 2 switch learn from an arriving frame?

A switch records the source MAC address and the ingress port in its MAC address table. Dynamically learned entries age out after a period without traffic.

How does a switch handle known and unknown destination MAC addresses?

A known destination is forwarded only through its associated port, unless that is the ingress port. An unknown destination is flooded out eligible ports in the same VLAN, except the ingress port.

What broadcast-domain effect does a VLAN have?

A VLAN is a separate Layer 2 broadcast domain. VLANs help contain broadcasts and organize devices, but do not alone provide a complete security boundary.

How does an access port carry VLAN traffic?

An access port normally carries one VLAN. Frames to and from the end device are untagged, and the switch associates incoming frames with the port’s configured access VLAN.

What does the native VLAN do on an 802.1Q trunk?

An 802.1Q trunk carries multiple VLANs and tags frames to identify their VLAN. The native VLAN carries untagged traffic, so its setting should match at both ends.

What is required for hosts in different VLANs to communicate?

Hosts in different VLANs need a router or Layer 3 switch to communicate. Each host uses the IP address of its VLAN’s router interface as its default gateway.

How does router-on-a-stick provide gateways for multiple VLANs?

A router connects to the switch through one trunk, and router subinterfaces provide gateways for multiple VLANs.

How does STP manage redundant Layer 2 links?

STP prevents Layer 2 loops by placing redundant paths in a nonforwarding state while retaining a backup path that can be activated if the active path fails.

How does STP elect the root bridge?

The root bridge is the switch with the lowest bridge ID. Configured priority is compared first, and MAC address breaks a tie.

How do PortFast and BPDU Guard work together?

PortFast lets a host-facing edge port transition rapidly to forwarding. BPDU Guard disables a PortFast-enabled port if it receives a BPDU.

How does EtherChannel appear to STP, and how may one flow use the bundle?

EtherChannel bundles physical links into one logical link. STP treats a correctly formed bundle as one logical port, and a single conversation may use only one member link.

What LACP modes are needed for two sides to negotiate a channel?

LACP active initiates negotiation, while passive responds. At least one side must be active for LACP to form the channel.