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Difficulty: MediumTroubleshooting IP Addressing and DHCP Services

A network technician is troubleshooting a newly connected client workstation that cannot access local network resources or the internet. Executing `ipconfig /all` on the workstation yields the following output:

Ethernet adapter Ethernet0:
Connection-specific DNS Suffix . :
Link-local IPv6 Address . . . . . : fe80::d4a2:810f:3c21:7a9a%12
IPv4 Address. . . . . . . . . . . : 169.254.108.42
Subnet Mask . . . . . . . . . . . : 255.255.0.0
Default Gateway . . . . . . . . . :

Which of the following is the most likely cause of this workstation's IP configuration?

  1. The host was unable to obtain an IP lease from a DHCP server and self-assigned an Automatic Private IP Addressing (APIPA) address.Answer
  2. B
    The default gateway parameter was left blank in the static IPv4 configuration properties, forcing the OS to default to a link-local range.
  3. C
    The workstation's static IP address and default gateway address reside on mismatched IPv4 subnets.
  4. D
    The central DHCP server scope ran out of usable host addresses because the subnet mask was set to calculate usable hosts without subtracting network and broadcast identifiers.

Answer

The host was unable to obtain an IP lease from a DHCP server and self-assigned an Automatic Private IP Addressing (APIPA) address.
An IPv4 address beginning with 169.254.x.x indicates Automatic Private IP Addressing (APIPA). Operating systems assign an APIPA address when configured as a DHCP client but fail to receive a response (DHCPACK) from a reachable DHCP server.

Step-by-Step Solution

1
Analyze the IP address output from the client workstation command prompt.
The IPv4 address is 169.254.108.42 with a subnet mask of 255.255.0.0.
Recognizing the address range helps identify how the host acquired its network settings.
2
Identify the standard protocol associated with the 169.254.0.0/16 address space.
The range 169.254.0.1 through 169.254.255.254 is reserved for Automatic Private IP Addressing (APIPA).
Client operating systems dynamically generate an APIPA address when DHCP DORA messages fail to produce a lease.
3
Deduce the primary root cause of the issue.
The workstation failed to contact a DHCP server, resulting in local link-local address generation.
Without a valid DHCP lease or static assignment, network layer routing beyond the immediate link is unviable.

Key Concept

Automatic Private IP Addressing (APIPA) Diagnosis
Estimated Time:1m 15s
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Topics

Troubleshooting IP Addressing and DHCP Services

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