A network technician provisions a new database server on VLAN 50 (10.50.0.0/24). Upon boot… — CompTIA Network+

A network technician provisions a new database server on VLAN 50 ( $10.50.0.0/24$ ). Upon booting up, running `ip addr show` reveals that the host interface has acquired an IP address of $169.254.88.12/16$ . The technician manually assigns a static address of $10.50.0.50/24$ to the interface and verifies that the host can successfully ping its default gateway at $10.50.0.1$ . The centralized DHCP server resides on VLAN 10 ( $10.10.0.5/24$ ).

Which of the following are the MOST likely causes of the host initially receiving an APIPA address? (Select TWO.)

The router interface serving VLAN 50 is missing an IP helper address pointing to the DHCP server at $10.10.0.5$ .Cevap
B
The server's default gateway address was incorrectly set to $10.10.0.5$ instead of $10.50.0.1$ .
The centralized DHCP server does not have an active IP scope configured for the $10.50.0.0/24$ network segment.Cevap
D
The $10.50.0.0/24$ subnet mask on the client blocks Layer 2 broadcast transmission of the initial DHCP DISCOVER frame.

Cevap

The host received an APIPA address because the router interface for VLAN 50 lacks an IP helper address pointing to the remote DHCP server, or the DHCP server lacks an active scope for the 10.50.0.0/24 subnet.

An APIPA address (169.254.x.x) confirms that the client failed to receive a response from a DHCP server. Since static IP configuration proves local VLAN 50 Layer 2 and Layer 3 connectivity to the default gateway is operational, the failure stems from cross-VLAN DHCP transport or pool availability. First, routers block broadcast traffic by default; thus, the router interface on VLAN 50 must have an IP helper address configured to forward DHCP broadcasts as unicast traffic to the DHCP server on VLAN 10. Second, the DHCP server must have an active address scope for the 10.50.0.0/24 network segment to lease addresses to clients on that relay pool.

Adım Adım Çözüm

Analyze the client IP address symptom

The host obtained 169.254.88.12/16, which is an APIPA address indicating that the client sent DHCP DISCOVER frames but never received a valid DHCP OFFER/ACK.

Identifying APIPA establishes that DHCP negotiation failed completely rather than succeeding with bad option settings.

Evaluate local Layer 2 connectivity

Static configuration of 10.50.0.50/24 successfully pings the gateway at 10.50.0.1.

This rules out physical cable failure, switch port VLAN misassignment, or default gateway interface shutdown.

Diagnose cross-subnet DHCP forwarding and scope availability

Because the DHCP server is located on VLAN 10 (10.10.0.5) while the host is on VLAN 50 (10.50.0.0/24), the router interface for VLAN 50 must act as a DHCP relay agent using `ip helper-address 10.10.0.5`. Furthermore, the DHCP server must hold an active pool matching the 10.50.0.0/24 network.

Without the relay agent, broadcast DISCOVER messages cannot cross Layer 3 boundaries. Without an active scope, the server cannot offer an address for that subnet.

Anahtar Kavram

DHCP Relay and Scope Configuration in Multi-VLAN Environments

Soru

Cevap

Adım Adım Çözüm

Anahtar Kavram

Sık Yapılan Hatalar

Konular

Bu konudan daha fazla soru