GCIH · Question #703
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?
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).
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
How the community answered
(48 responses)- A4% (2)
- B92% (44)
- C2% (1)
- D2% (1)
Why each option
Ethernet switches operate at OSI Layer 2 and forward frames by looking up the destination MAC address in their MAC address table (CAM table).
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.
A switch maintains a MAC address table that maps each learned destination MAC address to a specific port. When an Ethernet frame arrives, the switch reads the destination MAC address from the frame header and forwards the frame only to the port associated with that address, providing efficient unicast delivery across the LAN segment.
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.
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
Source: https://www.cisco.com/c/en/us/support/docs/switches/catalyst-6500-series-switches/10681-41.html
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