A network technician is troubleshooting connectivity failures on a newly provisioned branc… — CompTIA Network+

A network technician is troubleshooting connectivity failures on a newly provisioned branch office subnet, VLAN 70 ( $10.70.0.0/23$ ). Client workstations connected to VLAN 70 fail to access corporate resources and receive autoconfigured IP addresses in the range $169.254.18.1$ to $169.254.18.254$ with a subnet mask of $255.255.0.0$ . The centralized DHCP server resides on VLAN 10 ( $10.10.0.50$ ). Inspection of the Layer 3 switch reveals that Interface VLAN 70 is configured with IP address $10.70.0.1/23$ , but no IP helper address is configured, and logging on the DHCP server indicates that the IP pool for $10.70.0.0/23$ has reached $100\%$ capacity.

Which of the following factors explain why client devices are assigned $169.254.x.x$ addresses and detail the required remediation steps? (Select TWO.)

The generation of $169.254.x.x$ IP addresses indicates that client endpoints entered Automatic Private IP Addressing (APIPA) mode after failing to receive a valid DHCP lease response.Cevap
The Layer 3 interface for VLAN 70 must be configured with `ip helper-address 10.10.0.50` and the DHCP server scope for VLAN 70 must be expanded.Cevap
C
The $169.254.x.x$ address indicates that client workstations successfully reached the default gateway but failed domain name resolution (DNS).
D
Client workstations can reach the central DHCP server directly without a relay agent if the client subnet mask is modified from $/23$ to $/16$ .

Cevap

Clients receive APIPA addresses (169.254.x.x) because DHCPDISCOVER broadcasts fail to receive a lease response across subnets. Resolving the issue requires configuring `ip helper-address 10.10.0.50` on Interface VLAN 70 to relay DHCP broadcasts to the central server and expanding the exhausted DHCP scope for VLAN 70.

Client endpoints assign themselves APIPA addresses (

169.254.x.x

) when DHCPDISCOVER broadcast requests receive no response. Because the central DHCP server resides on a different subnet (VLAN 10), the Layer 3 switch interface serving VLAN 70 requires an `ip helper-address 10.10.0.50` statement to relay broadcast DHCP packets as unicast traffic to the server. Furthermore, because the server scope for VLAN 70 is at 100% capacity, the scope pool size must be expanded to grant new leases.

Adım Adım Çözüm

Diagnose the symptom associated with the

169.254.x.x

address block.

Identify that

169.254.0.0/16

is an Automatic Private IP Addressing (APIPA) address assigned automatically when an endpoint fails to locate or receive a response from a DHCP server.

Client operating systems invoke APIPA when DHCP lease requests (DORA process) time out.

Analyze cross-subnet DHCP traffic requirements.

Recognize that DHCPDISCOVER messages are Layer 2 broadcasts that cannot cross Layer 3 router boundaries by default.

The Layer 3 switch interface serving VLAN 70 must be configured with a DHCP relay command (`ip helper-address 10.10.0.50`) to convert broadcast requests into targeted unicast traffic directed to the DHCP server on VLAN 10.

Evaluate DHCP server pool utilization.

Identify scope exhaustion on the DHCP server as a secondary blocking factor for IP address allocation.

Even if relaying is functional, an exhausted scope prevents the DHCP server from offering valid IP leases to requesting endpoints.

Anahtar Kavram

DHCP Relay (IP Helper) Configuration and APIPA Fallback Behavior

Tahmini Süre:2m 0s

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