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Zorluk: Çok zorTroubleshooting IP Addressing and DHCP Services

Following a network resegmentation, a workstation on VLAN 30 (192.168.30.0/24192.168.30.0/24) is unable to communicate with network resources. The workstation's network adapter is set to acquire an IP address automatically. Running `ipconfig /all` on the workstation yields the following output:

IPv4 Address. . . . . . . . . . . . : 169.254.48.19
Subnet Mask . . . . . . . . . . . . : 255.255.0.0
Default Gateway . . . . . . . . . . :
DHCP Server . . . . . . . . . . . . :

The central DHCP server resides on VLAN 10 (192.168.10.15192.168.10.15). The network administrator inspects the router's configuration for the subinterface corresponding to VLAN 30 and notes that the interface is operational with IP 192.168.30.1/24192.168.30.1/24, but no relay commands are present.

Which of the following statements accurately diagnose this issue and identify the necessary corrective action? (Select TWO.)

  1. The workstation has self-assigned an APIPA address because its DHCPDISCOVER broadcast failed to receive a DHCPOFFER from the central DHCP server.Cevap
  2. An IP helper address pointing to 192.168.10.15 must be configured on the router's VLAN 30 interface to forward DHCP broadcast requests to the central server across subnets.Cevap
  3. C
    The workstation's default gateway address was statically misconfigured, preventing the client from contacting the DHCP server on VLAN 10.
  4. D
    The DHCP scope for VLAN 30 must be expanded because a 169.254.x.x address indicates that all usable host addresses in the 192.168.30.0/24 subnet have been exhausted.

Cevap

The workstation self-assigned an APIPA address due to an unfulfilled DHCP request, and an IP helper address pointing to 192.168.10.15 must be configured on the router's VLAN 30 interface.
The workstation's assignment of a 169.254.48.19 address confirms APIPA auto-configuration after failing to receive a response to its broadcast DHCPDISCOVER request. Because the DHCP server resides on a different VLAN/subnet (VLAN 10), the router interface for VLAN 30 requires a DHCP relay agent (IP helper address) to convert local broadcasts into unicast traffic directed to 192.168.10.15.

Adım Adım Çözüm

1
Analyze the client IP address from the output snippet.
The IP address 169.254.48.19 falls within the 169.254.0.0/16 range, confirming the client generated an APIPA address after receiving no response to dynamic IP addressing requests.
APIPA is activated automatically by host OSs when DHCP discovery times out.
2
Analyze the network topology and router configuration.
The client is on VLAN 30 (192.168.30.0/24) while the DHCP server is on VLAN 10 (192.168.10.15). Routers do not forward Layer 2 broadcasts between subnets by default.
DHCPDISCOVER packets use broadcast address 255.255.255.255, which is blocked at Layer 3 boundaries.
3
Determine the necessary remediation on the gateway router.
Configure `ip helper-address 192.168.10.15` under the VLAN 30 interface.
The IP helper agent converts broadcast DHCP requests into unicast packets directed to the DHCP server's IP address.

Anahtar Kavram

DHCP Relay and APIPA Troubleshooting
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