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101 · Question #585

A BIG IP Administrator is trying to reach the internal web server from a workstation: The workstation has a MAC address of 00:00:00:00:00:01and an IP address or 192.168.0.1 An internal web server has

The correct answer is C. 00:00:00:00:00:03. When a workstation sends a packet to a destination on a different IP subnet, it encapsulates the packet with the default gateway's MAC address as the Layer 2 destination.

Section 1: OSI Model, Network, and Application Delivery Basics

Question

A BIG IP Administrator is trying to reach the internal web server from a workstation:

  • The workstation has a MAC address of 00:00:00:00:00:01and an IP address or 192.168.0.1
  • An internal web server has a MAC address of 00:00:00:00:00:02 and an IP address of 10.10.1.1
  • The workstations default gateway has a MAC address of 00:00:00:00:00:03and IP address of

192.168.0.254 What is the destination hardware address of the outbound packet when it leaves the workstation?

Options

  • A00:00:00:00:00:01
  • B00:00:00:00:00:00
  • C00:00:00:00:00:03
  • D00:00:00:00:00:02

How the community answered

(35 responses)
  • A
    6% (2)
  • B
    17% (6)
  • C
    71% (25)
  • D
    6% (2)

Why each option

When a workstation sends a packet to a destination on a different IP subnet, it encapsulates the packet with the default gateway's MAC address as the Layer 2 destination.

A00:00:00:00:00:01

00:00:00:00:00:01 is the workstation's own MAC address and would only appear as the source hardware address, never the destination in an outbound packet.

B00:00:00:00:00:00

00:00:00:00:00:00 is the all-zeros broadcast placeholder and is not a valid unicast destination MAC address for a routed packet.

C00:00:00:00:00:03Correct

The workstation's destination IP (10.10.1.1) is in a different subnet than its own (192.168.0.0/24). Per IP routing rules, the workstation recognizes the destination is not local and forwards the packet to its default gateway (192.168.0.254). The Ethernet frame is addressed to the gateway's MAC address 00:00:00:00:00:03 so the gateway can receive and route the packet onward.

D00:00:00:00:00:02

00:00:00:00:00:02 is the web server's MAC address, but the workstation has no ARP entry for a host on a remote subnet - it can only address devices on its local segment at Layer 2.

Concept tested: Layer 2 destination MAC for inter-subnet routing

Source: https://www.rfc-editor.org/rfc/rfc826

Topics

#MAC address#default gateway#ARP#Layer 2 forwarding

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