A network administrator is troubleshooting DHCP lease failures for client devices on a newly established remote subnet (). The centralized DHCP server resides on a core management subnet (). Packet captures on the client-facing Layer 3 interface confirm that client broadcast DHCPDISCOVER packets are arriving at the local gateway, but no request packets are reaching the DHCP server. Which of the following statements correctly describe the required configuration and protocol behavior of the DHCP relay agent in this scenario? (Select TWO)
- The `ip helper-address 10.100.1.24` command must be applied directly to the client-facing Layer 3 interface serving as the default gateway for the subnet.Answer
- The relay agent converts the client's broadcast request into a unicast UDP packet directed to destination port 67 on the centralized DHCP server.Answer
- CThe relay agent encapsulates the DHCP payload inside a TCP segment targeted at destination port 68 to ensure reliable delivery across subnets.
- DThe `ip helper-address` command must be configured on the router's egress WAN interface facing the DHCP server rather than the client-facing gateway interface.
Answer
The correct statements are that the `ip helper-address` command must be applied to the client-facing Layer 3 interface, and that the relay agent converts the broadcast request into a unicast UDP packet directed to port 67 on the DHCP server.
DHCP relay agents (configured via `ip helper-address` on Cisco/standard network equipment) must be placed on the client-facing interface so the router intercepts client broadcast packets at the Layer 3 ingress boundary. The relay agent populates the `giaddr` (Gateway IP Address) field with its local interface address, converts the broadcast into a unicast packet, and forwards it over UDP port 67 to the DHCP server address specified in the helper configuration.
Step-by-Step Solution
Key Concept
DHCP Relay Agent Architecture and IP Helper Operations