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An enterprise network architect is designing a multi-VRF network infrastructure where clients in remote subnets must receive IP leases from a centralized DHCP server cluster while maintaining accurate physical switch-port tracking and automated domain name registration. Which TWO of the following configurations or mechanisms must be implemented to fulfill these requirements?

  1. Enable DHCP Relay (IP Helper) on the remote subnet default gateway interfaces to append Option 82 sub-options (Circuit ID and Remote ID) before forwarding requests to the central DHCP server.Cevap
  2. Configure Client FQDN (Option 81) or secure Dynamic DNS (DDNS) updates on the DHCP server to automatically register forward (A/AAAA) and reverse (PTR) records with authoritative DNS servers.Cevap
  3. C
    Replace the standard A/AAAA resource records on the central DNS server with CNAME alias records that point directly to the subnet broadcast address of each remote relay agent.
  4. D
    Position the DHCP Relay Agent service exclusively on the centralized DHCP server host interface rather than on the remote default gateway interfaces.
  5. E
    Reconfigure the DHCP relay agents and central DHCP server to establish communication using TCP port 67 to encrypt packet headers across intermediate routers.

Cevap

The two correct requirements are configuring DHCP Relay on default gateway interfaces to insert Option 82 relay information, and enabling DHCP Option 81 (Client FQDN) / secure Dynamic DNS updates on the DHCP server.
Enabling DHCP Relay with Option 82 on remote subnet gateway interfaces allows the network to relay client requests across Layer 3 boundaries while attaching switch port and circuit metadata. In addition, using Option 81 (Client FQDN) / DDNS on the DHCP server ensures seamless, automated updating of A, AAAA, and PTR records in authoritative DNS zones whenever leases are granted.

Adım Adım Çözüm

1
Analyze the requirement for tracking physical location/switch-port details across Layer 3 boundaries.
Identified that DHCP Relay Agent Information (Option 82) must be inserted at the Layer 3 boundary interface (default gateway) to provide Circuit ID and Remote ID metadata to the DHCP server.
Broadcast DHCP requests cannot cross routers without a relay agent, and Option 82 supplies switch port and agent identity to the centralized server.
2
Analyze the requirement for automated domain name registration across IP addressing services.
Identified DHCP Option 81 (Client FQDN) and secure Dynamic DNS (DDNS) integration between DHCP and DNS infrastructure.
Option 81 allows the DHCP server to negotiate and execute dynamic updates for forward (A/AAAA) and reverse (PTR) lookup records upon issuing an IP address lease.
3
Evaluate and discard distractor options based on architectural error taxonomy.
Eliminated incorrect relay placement (must be on remote gateway, not central server host), incorrect protocol/port (DHCP uses UDP 67/68, not TCP 67), and invalid DNS record usage (CNAME pointing to broadcast address).
Ensures architectural compliance with CompTIA Network+ standards for IP services.

Anahtar Kavram

DHCP Relay Architecture, Option 82 (Relay Agent Information), and Option 81 / DDNS Integration
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