GCIH Question #703: Real Exam Question with Answer & Explanation

The correct answer is B: Destination MAC address. Ethernet switches operate at OSI Layer 2 and forward frames by looking up the destination MAC address in their MAC address table (CAM table).

Reconnaissance, Scanning, and Enumeration

Question

When switching traffic on a LAN, what element of the Ethernet frame does a switch use to make its decision on where to send the data?

Options

ADestination IP address
BDestination MAC address
CDestination ARP response
DSource DHCP packet

Explanation

Ethernet switches operate at OSI Layer 2 and forward frames by looking up the destination MAC address in their MAC address table (CAM table).

Common mistakes.

A. Destination IP addresses are Layer 3 identifiers processed by routers, not switches; standard Layer 2 switches do not inspect the IP header for forwarding decisions.
C. ARP responses are used to resolve an IP address to a MAC address at the network level, but ARP is not a field within an Ethernet frame that a switch uses for its forwarding decision.
D. DHCP packets are application-layer messages that dynamically assign IP addresses and are not elements of the Ethernet frame used by a switch to determine where to send traffic.

Concept tested. Layer 2 switch forwarding using destination MAC address

Reference. https://www.cisco.com/c/en/us/support/docs/switches/catalyst-6500-series-switches/10681-41.html

Topics

#Ethernet#MAC address#switching#networking fundamentals

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