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Zorluk: KolayIP Addressing and Network Configuration

A user reports that their desktop computer cannot access any network resources or the internet. A technician opens the command prompt on the computer, runs the `ipconfig` command, and receives an IP address of `169.254.45.12` with a subnet mask of `255.255.0.0`. Which of the following is the most likely cause of this network issue?

  1. The computer was unable to contact a DHCP server and automatically assigned itself an Automatic Private IP Addressing (APIPA) address.Cevap
  2. B
    The local DNS server is offline and failing to issue dynamic IP address leases to network hosts.
  3. C
    The default gateway router is actively dropping Layer 2 switch traffic within the local subnet boundary.
  4. D
    The workstation's network adapter is configured to request IP configurations using secure HTTPS port 443 instead of HTTP port 80.

Cevap

The client failed to contact a DHCP server, resulting in an automatically assigned APIPA (169.254.x.x) address.
An IP address starting with 169.254.x.x indicates Automatic Private IP Addressing (APIPA). When a network host configured for dynamic IP addressing sends out a DHCP Discover message and does not receive a response from a DHCP server, the operating system self-assigns an APIPA address to allow local Link-Local communication. Because APIPA addresses are non-routable, the workstation cannot access external subnets or the internet.

Adım Adım Çözüm

1
Analyze the IP address obtained from the ipconfig output.
The IP address is 169.254.45.12 with a subnet mask of 255.255.0.0.
Recognizing the address range identifies the mechanism responsible for assigning it.
2
Identify the standard address allocation standard for 169.254.0.0/16.
The address falls into the IPv4 Automatic Private IP Addressing (APIPA) block.
Operating systems generate an APIPA address when configured for dynamic IP discovery (DHCP) but receive no response from a DHCP server.
3
Determine the root cause of the issue.
DHCP server unreachability or network failure preventing DHCP communication.
Because APIPA is a fallback mechanism, the primary issue is the client's failure to obtain a valid lease from a functional DHCP server.

Anahtar Kavram

Automatic Private IP Addressing (APIPA)
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