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Difficulty: EasyTroubleshooting IP Addressing and DHCP Services

A workstation on a corporate network is unable to connect to local network resources or access the internet. A technician executes `ipconfig /all` on the workstation and observes an IPv4 address of 169.254.45.12169.254.45.12 with a subnet mask of 255.255.0.0255.255.0.0. Which of the following is the most likely cause of this connectivity issue?

  1. The workstation failed to obtain an IP lease from a DHCP server and assigned itself an Automatic Private IP Addressing (APIPA) address.Answer
  2. B
    The workstation's default gateway IP address resides on an incorrect subnet, blocking external communication.
  3. C
    The network administrator configured a subnet mask that includes the network broadcast address as a usable host address.
  4. D
    The local DHCP relay agent was improperly enabled on the central server interface rather than the client gateway subinterface.

Answer

The workstation failed to contact a DHCP server to acquire an IP address lease, resulting in the self-assignment of an Automatic Private IP Addressing (APIPA) address.
An IP address starting with 169.254.x.x169.254.x.x (specifically in the 169.254.0.0/16169.254.0.0/16 range) is an Automatic Private IP Address (APIPA). Operating systems assign an APIPA address when a DHCP client is unable to contact a DHCP server to obtain an IP address lease. Because APIPA addresses are non-routable, the host cannot communicate beyond its local layer 2 segment.

Step-by-Step Solution

1
Analyze the reported IPv4 address snippet from ipconfig output.
The workstation reports 169.254.45.12169.254.45.12 with subnet mask 255.255.0.0255.255.0.0.
The address range 169.254.0.0/16169.254.0.0/16 is reserved by IANA for IPv4 link-local addressing (APIPA).
2
Identify the mechanism that generates addresses in the 169.254.0.0/16 range.
Host OS automatically generates an APIPA address when dynamic configuration (DHCP) fails.
When a client sends a DHCPDISCOVER broadcast and receives no DHCPOFFER within the timeout period, it defaults to APIPA to allow limited local link communication.
3
Select the option describing failed DHCP acquisition and APIPA generation.
Confirm that failing to reach a DHCP server and assigning an APIPA address is the root symptom.
This directly explains both the specific IP address assigned and the inability to route to external or non-link-local network resources.

Key Concept

Automatic Private IP Addressing (APIPA) Diagnosis
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Topics

Troubleshooting IP Addressing and DHCP Services

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