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SK0-004 · Question #27

A new DHCP server is placed on a network segment during off hours. When work resumes, users on a different network segment report connectivity issues. Users on the same network segment report no…

The correct answer is C. The DHCP relay agent was not configured on the adjacent network segment. DHCP broadcast packets do not cross router boundaries, so clients on a remote segment require a DHCP relay agent configured on that segment's router interface to forward requests to the new DHCP server.

Troubleshooting

Question

A new DHCP server is placed on a network segment during off hours. When work resumes, users on a different network segment report connectivity issues. Users on the same network segment report no connectivity issues. Which of the following is the MOST likely reason for the connectivity issues?

Options

  • AThe DHCP server was configured without specifying a WINS server address for the users.
  • BThe DHCP server was configured without specifying a DNS server address for the users.
  • CThe DHCP relay agent was not configured on the adjacent network segment.
  • DThe DHCP server was configured to use private IP addressing to all network segments.

How the community answered

(20 responses)
  • A
    15% (3)
  • B
    20% (4)
  • C
    60% (12)
  • D
    5% (1)

Why each option

DHCP broadcast packets do not cross router boundaries, so clients on a remote segment require a DHCP relay agent configured on that segment's router interface to forward requests to the new DHCP server.

AThe DHCP server was configured without specifying a WINS server address for the users.

WINS provides NetBIOS name resolution and its absence affects name lookup only; it would not cause IP-layer connectivity failures for an entire network segment.

BThe DHCP server was configured without specifying a DNS server address for the users.

A missing DNS server address would cause name resolution failures across all segments served by the DHCP server, not selectively on only the remote segment.

CThe DHCP relay agent was not configured on the adjacent network segment.Correct

DHCP uses Layer 2 broadcasts that are blocked at router interfaces by default. A DHCP relay agent (IP helper) must be configured on the router interface facing the adjacent segment to intercept those broadcasts and forward them as unicast packets to the DHCP server. Without this relay, clients on the remote segment never receive DHCP offers, causing them to fall back to APIPA addresses or lose connectivity entirely.

DThe DHCP server was configured to use private IP addressing to all network segments.

Using private IP addressing for all segments is standard practice and does not inherently cause connectivity problems for any specific segment.

Concept tested: DHCP relay agent enabling cross-segment address assignment

Source: https://learn.microsoft.com/en-us/windows-server/networking/technologies/dhcp/dhcp-relay-agent

Topics

#DHCP relay agent#network segments#DHCP configuration#IP addressing

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