Question

Difficulty: EasyTroubleshooting Routing, Default Gateways, and ACLs

A network technician is configuring a workstation with the IP address 192.168.1.45 and a subnet mask of 255.255.255.0. The technician manually sets the workstation's default gateway address to 192.168.2.1. The workstation can communicate with other hosts on the 192.168.1.0/24 subnet but cannot reach any internet destinations. Which of the following is the most likely cause of this issue?

  1. The default gateway address is configured on a different IP subnet than the workstation.Answer
  2. B
    The workstation was assigned a network address instead of a usable host IP address.
  3. C
    The workstation's outbound traffic is being blocked by an implicit deny rule on a firewall.
  4. D
    The workstation requires 802.1Q VLAN tagging to communicate across separate broadcast domains.

Answer

The default gateway address is configured on a different IP subnet than the workstation.
For a workstation to send traffic to external networks, its default gateway must be on the same local IP subnet. With an IP of 192.168.1.45/24, the gateway must be an address within 192.168.1.0/24 (such as 192.168.1.1). Configuring 192.168.2.1 makes the gateway unreachable at Layer 2.

Step-by-Step Solution

1
Determine the host subnet boundaries.
An IP of 192.168.1.45 with mask 255.255.255.0 (/24) belongs to the 192.168.1.0/24 subnet with usable host IPs from 192.168.1.1 through 192.168.1.254.
Host IP configuration determines which addresses are considered local (on-link).
2
Compare the default gateway IP to the host subnet.
The IP address 192.168.2.1 belongs to the 192.168.2.0/24 subnet.
To route off-subnet traffic, the host must be able to send Ethernet frames directly to the gateway's IP address on the local segment.
3
Identify the connectivity impact.
Because 192.168.2.1 is off-link, the workstation cannot send ARP requests directly to resolve the gateway's MAC address, preventing remote communication.
Default gateways must be local host neighbors on the same IP subnet.

Key Concept

Default Gateway Subnet Alignment
Estimated Time:45s
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