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Difficulty: MediumTroubleshooting IP Addressing and DHCP Services

Users in a regional branch office report that their workstations can successfully communicate with local peers on their LAN segment but are unable to access centralized enterprise resources hosted at 10.50.0.0/2410.50.0.0/24. A network technician executes `ipconfig /all` on a affected workstation and receives the following output:

text
IPv4 Address. . . . . . . . . . . : 192.168.45.112
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.4.1
DHCP Server . . . . . . . . . . . : 192.168.45.1

Which of the following represents the root cause of the routing failure to external subnets?

  1. The configured default gateway address resides on a different IP subnet than the host address.Answer
  2. B
    The host failed to receive a DHCP lease and automatically assigned itself an APIPA address.
  3. C
    The router interface connecting the local network is missing an IP helper address to relay DHCP requests.
  4. D
    The assigned IPv4 address corresponds to the unusable network identifier of the subnet.

Answer

The configured default gateway address resides on a different IP subnet than the host address.
The correct answer identifies that the default gateway (192.168.4.1) is misconfigured on a different subnet than the host (192.168.45.112/24). A default gateway must reside within the host's local IP subnet so the host can perform ARP resolution and send non-local packets to the gateway router.

Step-by-Step Solution

1
Analyze host IP parameters from ipconfig output
Host IP is 192.168.45.112192.168.45.112 with subnet mask 255.255.255.0255.255.255.0 (/24), defining the local subnet range as 192.168.45.1192.168.45.1 to 192.168.45.254192.168.45.254.
Determines the boundaries of the local broadcast domain.
2
Evaluate the configured default gateway address
Default Gateway is set to 192.168.4.1192.168.4.1, which resides in the 192.168.4.0/24192.168.4.0/24 network range.
Identifies whether the gateway is directly reachable on the local layer 2 segment.
3
Determine the impact on traffic destined for remote networks
Because 192.168.4.1192.168.4.1 is not on the 192.168.45.0/24192.168.45.0/24 subnet, local ARP requests for the gateway's MAC address fail, rendering external subnets unreachable while local subnet traffic continues to function.
Explains why intra-subnet connectivity works but remote traffic fails.

Key Concept

Default Gateway Subnet Misconfiguration
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Topics

Troubleshooting IP Addressing and DHCP Services

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