A systems administrator is manually assigning a static IP configuration to a new server on… — CompTIA A+ (Core 1 & Core 2)

A systems administrator is manually assigning a static IP configuration to a new server on a corporate network segment designated as $10.20.30.0/24$ . The server is configured with an IPv4 address of $10.20.30.50$ and a subnet mask of $255.255.255.0$ . The administrator enters $10.20.31.1$ into the default gateway field. During post-configuration testing, workstations on the local $10.20.30.0/24$ subnet can successfully access services on the server, but remote hosts on other corporate subnets cannot establish a connection to it. Which of the following is the most likely cause of this network issue?

The default gateway is configured with an IP address outside the host's local subnet.Answer
B
The server automatically defaulted to an APIPA IP address because the DHCP server was unreachable.
C
The network switch connecting local hosts operates at Layer 2 and cannot forward frame headers across subnets.
D
The DNS server failed to lease a valid default gateway address to the host during network startup.

Answer

The default gateway is configured with an IP address outside the host's local subnet.

For a host to communicate with remote networks, its default gateway must reside within the same local IP subnet as the host's IP address. With an IP of

10.20.30.50

and a

/24

subnet mask (

255.255.255.0

), valid local gateway addresses must fall between

10.20.30.1

and

10.20.30.254

. Because

10.20.31.1

is on a different subnet, the server cannot ARP for the gateway, rendering off-subnet destination IPs unreachable while allowing local subnet traffic to function.

Step-by-Step Solution

Analyze the subnet mask and host IP configuration.

An IP address of

10.20.30.50

with a subnet mask of

255.255.255.0

(/24) defines a local broadcast domain spanning

10.20.30.1

through

10.20.30.254

Traffic within

10.20.30.0/24

does not require a router or default gateway to communicate directly via Layer 2 ARP.

Evaluate the configured default gateway address against the local subnet boundaries.

The configured gateway

10.20.31.1

belongs to the

10.20.31.0/24

subnet, which is outside the local

10.20.30.0/24

network segment.

A host must send packets destined for outside networks to a default gateway located within its own local subnet. Because

10.20.31.1

is on a different subnet, the host cannot resolve its MAC address locally to forward traffic off-subnet.

Key Concept

Subnet Boundaries and Default Gateway Assignment

Estimated Time:1m 30s

Question

Answer

Step-by-Step Solution

Key Concept

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