300-440 Question 274
Single answerA network administrator is troubleshooting a DHCP issue in an IPv4 and IPv6 dual-stack network. The administrator observes that IPv4 clients are not receiving IP addresses from the DHCP server, while IPv6 clients are functioning correctly. Upon reviewing the router configuration, the administrator notices that the DHCP server is configured, but the clients are still not getting addresses. What could be the most likely cause of the issue?
- A
The DHCP relay is not configured on the router for IPv4 traffic.
- B
The DHCP pool for IPv4 is exhausted on the DHCP server.
- C
The incorrect DHCP option is configured for IPv4 clients.
- D
The IPv6 DHCP pool is misconfigured and interfering with IPv4 DHCP operations.
Show answer and explanation
Correct answer: A
Explanation
In this scenario, the issue is isolated to IPv4 clients not receiving IP addresses. Since the DHCP server is configured, the most likely cause is that the DHCP requests from IPv4 clients are not reaching the server. This happens when the DHCP relay is not configured on the router for IPv4 traffic, as DHCP messages are broadcast and do not cross Layer 3 boundaries without a relay agent configured.
- A. Correct.
If the router is not configured as a DHCP relay for IPv4 traffic, the DHCP requests from clients may not reach the DHCP server, causing IPv4 address assignment to fail.
- B. Incorrect.
If the DHCP pool were exhausted, the administrator would see log messages indicating the pool is out of addresses. This is not mentioned in the scenario.
- C. Incorrect.
Misconfigured DHCP options would not prevent clients from obtaining an IP address altogether; it would typically cause misbehavior for specific features like PXE boot or domain name resolution.
- D. Incorrect.
IPv6 and IPv4 DHCP pools operate independently, so a misconfiguration in the IPv6 DHCP pool will not interfere with IPv4 DHCP operations.