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Zorluk: OrtaIP Addressing and Network Configuration

A technician is configuring network settings for a desktop computer in a newly created department segment. The computer is manually assigned a static IPv4 address of 192.168.50.75192.168.50.75, a subnet mask of 255.255.255.128255.255.255.128, a default gateway of 192.168.50.150192.168.50.150, and a DNS server address of 192.168.50.2192.168.50.2. Diagnostic testing reveals that the computer can successfully communicate with local host 192.168.50.10192.168.50.10, but cannot communicate with servers on external subnets or access the internet. Which of the following is the most likely cause of this issue?

  1. The configured default gateway resides outside the local IPv4 subnet defined by the subnet mask.Cevap
  2. B
    The workstation automatically assigned itself an APIPA address because the local DHCP server failed to respond.
  3. C
    The primary DNS server is responsible for issuing dynamic IP addresses and has experienced a service failure.
  4. D
    An unmanaged Layer 2 switch must be installed to connect the workstation across differing IP subnet boundaries.

Cevap

The configured default gateway resides outside the local IPv4 subnet defined by the subnet mask.
The subnet mask 255.255.255.128255.255.255.128 (/25) creates subnets with 128 total IP addresses each. The first subnet spans from 192.168.50.0192.168.50.0 to 192.168.50.127192.168.50.127 (usable range 192.168.50.1192.168.50.1–192.168.50.126192.168.50.126). Because the host's IP address is 192.168.50.75192.168.50.75, it resides in this first subnet. However, the configured default gateway address 192.168.50.150192.168.50.150 falls into the second subnet (192.168.50.128192.168.50.128 to 192.168.50.255192.168.50.255). A host cannot send packets directly to a gateway outside its local subnet boundaries, causing off-subnet communication to fail while local intra-subnet communication succeeds.

Adım Adım Çözüm

1
Analyze the subnet mask to determine network boundaries
A subnet mask of 255.255.255.128255.255.255.128 represents a /25 prefix, dividing the octet into block sizes of 128 addresses (256−128=128256 - 128 = 128).
Subnet masks determine which portion of an IP address represents the network ID and host ID.
2
Identify the host's subnet address range
For network 192.168.50.0/25192.168.50.0/25, the first subnet range is 192.168.50.0192.168.50.0 to 192.168.50.127192.168.50.127, with usable host addresses from 192.168.50.1192.168.50.1 to 192.168.50.126192.168.50.126.
The host IP address 192.168.50.75192.168.50.75 falls within this first subnet range.
3
Evaluate the default gateway IP address against the host subnet range
The gateway address 192.168.50.150192.168.50.150 belongs to the second subnet (192.168.50.128192.168.50.128 to 192.168.50.255192.168.50.255).
A host cannot send packets directly to a default gateway that is not located on its own local subnet segment.

Anahtar Kavram

Subnet Mask Boundaries and Default Gateway Assignment
Tahmini Süre:1m 15s
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IP Addressing and Network Configuration

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