SK0-005 · Question #390
A systems engineer is configuring a new VLAN for expansion of a campus network. The engineer configures a new DHCP scope on the existing Windows DHCP server cluster and activates the scope for the cli
The correct answer is C. Confirm the network has a helper address for the DHCP server.. When DHCP clients on a new VLAN cannot obtain IP addresses from a DHCP server on a different subnet, the most common issue is the lack of a DHCP relay agent (helper address) to forward broadcast requests.
Question
A systems engineer is configuring a new VLAN for expansion of a campus network. The engineer configures a new DHCP scope on the existing Windows DHCP server cluster and activates the scope for the clients. However, new clients in the area report they are not receiving any DHCP address information. Which of the following should the engineer do first?
Options
- AConfirm the client PCs are using the correct speed on the NIC.
- BConfirm the network uses the same NTP server as the clients.
- CConfirm the network has a helper address for the DHCP server.
- DConfirm the DHCP server is authorized in Active Directory.
How the community answered
(43 responses)- A9% (4)
- B5% (2)
- C84% (36)
- D2% (1)
Why each option
When DHCP clients on a new VLAN cannot obtain IP addresses from a DHCP server on a different subnet, the most common issue is the lack of a DHCP relay agent (helper address) to forward broadcast requests.
NIC speed issues might cause network connectivity problems but are unlikely to specifically prevent DHCP address assignment while other network functions might still operate.
NTP server synchronization affects timekeeping but does not prevent DHCP clients from obtaining an IP address from a DHCP server.
DHCP requests are broadcast messages and do not cross router boundaries by default. If the DHCP server is on a different VLAN/subnet than the clients, a DHCP relay agent (configured as a helper address on the router or switch interface for that VLAN) is required to forward these requests to the DHCP server. Without this helper address, clients will not receive DHCP offers.
Authorizing a DHCP server in Active Directory is necessary for a Windows DHCP server to lease addresses, but this is a server-wide authorization, and the issue here is specific to a new VLAN where inter-subnet communication is failing.
Concept tested: DHCP relay agent / helper address
Source: https://learn.microsoft.com/en-us/windows-server/networking/technologies/dhcp/dhcp-relay-agent
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