nerdexam
Cisco

200-301 · Question #811

Which two of these functions do routers perform on packets? (Choose two.)

The correct answer is B. update the Layer 2 headers of outbound packets with the MAC addresses of the next hops D. examine the Layer 3 headers of inbound packets and use that information to determine the next. Routers examine the Layer 3 header of incoming packets to determine the next hop and then update the Layer 2 header of outgoing packets with the MAC address of that next hop.

Submitted by haruto_sh· Mar 5, 2026

Question

Which two of these functions do routers perform on packets? (Choose two.)

Options

  • Aupdate the Layer 3 headers of outbound packets so that the packets are properly directed to valid
  • Bupdate the Layer 2 headers of outbound packets with the MAC addresses of the next hops
  • Cexamine the Layer 3 headers of inbound packets and use that information to determine the
  • Dexamine the Layer 3 headers of inbound packets and use that information to determine the next
  • Eexamine the Layer 2 headers of inbound packets and use that information to determine the next
  • Fupdate the Layer 3 headers of outbound packets so that the packets are properly directed to their

How the community answered

(51 responses)
  • A
    6% (3)
  • B
    88% (45)
  • E
    4% (2)
  • F
    2% (1)

Why each option

Routers examine the Layer 3 header of incoming packets to determine the next hop and then update the Layer 2 header of outgoing packets with the MAC address of that next hop.

Aupdate the Layer 3 headers of outbound packets so that the packets are properly directed to valid

Routers do not typically change the Layer 3 destination IP address of a packet; they primarily decrement the Time-To-Live (TTL) field and recompute the header checksum.

Bupdate the Layer 2 headers of outbound packets with the MAC addresses of the next hopsCorrect

After a router determines the next hop for a packet based on its routing table, it reconstructs the Layer 2 frame for the outgoing interface, inserting the MAC address of the next-hop device or the final destination if directly connected, and its own MAC address as the source.

Cexamine the Layer 3 headers of inbound packets and use that information to determine the

This option is incomplete and does not fully describe a router's function, as it doesn't specify what information is determined from examining the Layer 3 headers.

Dexamine the Layer 3 headers of inbound packets and use that information to determine the nextCorrect

Upon receiving an inbound packet, a router examines the Layer 3 (IP) destination address in the packet header. It then uses this information to look up the best path in its routing table and determine the appropriate next-hop router or destination host.

Eexamine the Layer 2 headers of inbound packets and use that information to determine the next

While routers process Layer 2 headers to accept a frame, the decision for routing (determining the next hop) is based on the Layer 3 (IP) destination address, not Layer 2 information.

Fupdate the Layer 3 headers of outbound packets so that the packets are properly directed to their

Similar to option A, routers do not modify the Layer 3 destination IP address to direct packets; they forward based on the existing destination IP and their routing table.

Concept tested: Router packet forwarding process (Layer 2 and Layer 3)

Source: https://www.cisco.com/c/en/us/td/docs/ios/dial/configuration/guide/dia_cft.html

Topics

#Router functions#Packet forwarding#Layer 2 headers#Layer 3 headers

Community Discussion

No community discussion yet for this question.

Sign up to join the discussion
Full 200-301 Practice