A network administrator is configuring IP addressing services for a newly created client subnet (VLAN 30) across a routed enterprise network. The centralized DHCP server is located on a different subnet (VLAN 10). Users on VLAN 30 report that their workstations fail to acquire dynamic IP addresses and instead receive APIPA addresses in the range . Which configuration change must be implemented on the default gateway router interface for VLAN 30 to resolve this issue?
- Configure an IP helper address (DHCP relay agent) on the VLAN 30 gateway interface pointing to the DHCP server IP addressAnswer
- BConfigure a DHCP relay agent on the central DHCP server interface on VLAN 10 pointing back to the client subnet
- CCreate an AAAA resource record on the DNS server for the VLAN 30 default gateway interface
- DReconfigure the central DHCP server to listen for client lease requests over TCP port 67 instead of UDP port 67
Answer
Configure an IP helper address (DHCP relay agent) on the VLAN 30 gateway interface pointing to the DHCP server IP address
DHCP clients discover servers using local broadcasts. Because Layer 3 routers drop broadcast traffic by default, a DHCP relay agent (configured via an IP helper address on the router interface local to the client subnet) is required to translate client broadcast requests into unicast packets sent directly to the central DHCP server.
Step-by-Step Solution
Key Concept
DHCP Relay Agent and IP Helper Functionality across Layer 3 Subnet Boundaries