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Difficulty: Very hardIP Addressing and Network Configuration

A network administrator is assigning a static IPv4 configuration to a server interface intended to host internal services. The interface is configured with the IP address 192.168.4.150 and a subnet mask of 255.255.255.192. The default gateway setting is entered as 192.168.4.194, and the primary DNS server is set to 192.168.4.2.

After saving the configuration, local network tests reveal that the server can successfully communicate with hosts in the range 192.168.4.129 through 192.168.4.190, but packets destined for off-subnet remote networks fail to reach their destination. Meanwhile, a junior technician suggests changing the primary DNS setting because they believe DNS servers lease IP addresses and update router gateways.

Which of the following correctly identifies why the server cannot reach remote networks?

  1. The default gateway IP address resides outside the subnet boundary of the server's interface address, preventing off-subnet traffic forwarding.Answer
  2. B
    The primary DNS server IP address must be changed to the DHCP server address because DNS is responsible for assigning IP leases and gateway routes.
  3. C
    The server automatically reverted to an APIPA address because the gateway address failed to validate dynamic address lease requests.
  4. D
    An unmanaged Layer 2 switch connected to the server is failing to perform inter-VLAN routing across subnet boundaries.

Answer

The default gateway IP address resides outside the subnet boundary of the server's interface address, preventing off-subnet traffic forwarding.
The correct answer identifies that the default gateway address (192.168.4.194) is outside the host's subnet (192.168.4.128/26, usable range .129 to .190). A node must be on the same IPv4 subnet as its default gateway to resolve the gateway's MAC address via ARP.

Step-by-Step Solution

1
Determine the subnet subnetting parameters based on the network mask.
A subnet mask of 255.255.255.192 represents a /26 prefix length. The subnet increment (block size) in the fourth octet is 256−192=64256 - 192 = 64.
Calculating block size establishes the boundary markers for each subnet.
2
Identify the specific subnet range for the host IP address 192.168.4.150.
The host IP 192.168.4.150 falls within the fourth octet block starting at 128: Subnet ID: 192.168.4.128/26, Usable Range: 192.168.4.129 – 192.168.4.190, Broadcast: 192.168.4.191.
This establishes which IP addresses belong to the host's local broadcast domain.
3
Evaluate the location of the configured default gateway address 192.168.4.194.
The IP address 192.168.4.194 falls into the next subnet (192.168.4.192/26, range 192.168.4.193 – 192.168.4.254).
A host must be able to resolve the default gateway's MAC address directly on its local subnet via ARP. Since 192.168.4.194 is on a different subnet, the host cannot ARP for it directly, causing off-subnet packet transmission to fail.

Key Concept

IPv4 Subnet Boundaries & Default Gateway Placement
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Topics

IP Addressing and Network Configuration

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