A network technician is setting up network connectivity for a newly created department on a separate floor. All workstations are connected to a newly installed Layer 2 switch, which connects directly to a port on the building's core router serving as the default gateway. However, none of the departmental workstations can access network resources or the internet. Running `ipconfig` on the workstations reveals IP addresses in the network range. The enterprise DHCP server is located on a different IP subnet across the network core. Which device configuration or feature must be enabled on the router interface to resolve this issue?
- A DHCP relay agent (IP helper) enabled on the gateway router interfaceAnswer
- BAn unmanaged Layer 2 switch feature to forward broadcast frames across routed subnet boundaries
- CA local DNS server installation on the switch port to assign dynamic IP addresses using domain names
- DReplacement of all workstation network interface cards to address physical APIPA detection faults
Answer
Enabling a DHCP relay agent (also known as an IP helper address) on the gateway router interface allows Layer 2 DHCP broadcast requests from the local subnet to be forwarded as unicast traffic across subnet boundaries to the centralized DHCP server.
Workstations receiving addresses are utilizing Automatic Private IP Addressing (APIPA), indicating that client NICs are functional but cannot reach a DHCP server. Because DHCP discovery frames are Layer 2 broadcasts, the router separating the subnets drops these frames by default. Enabling a DHCP relay agent (IP helper) on the router's incoming interface allows the router to accept these broadcasts and forward them as unicast packets across subnets to the central DHCP server.
Step-by-Step Solution
Key Concept
DHCP Relay / IP Helper Agent on Layer 3 Devices
Estimated Time:2m 0s