Where does the configuration reside when a helper address is configured to support DHCP?
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A. B. C. D.B
When a helper address is configured to support DHCP, the configuration resides on the router closest to the
When a helper address is configured to support DHCP, the configuration resides on the router closest to the client.
In a network environment, when a DHCP client sends a DHCP request to obtain an IP address, it typically does so using a broadcast message. However, broadcasts are not forwarded across different network segments by routers. This means that if the DHCP server is located in a different network segment than the client, the client's broadcast DHCP request will not reach the server.
To overcome this limitation, Cisco devices provide a feature called DHCP Relay or IP Helper. This feature allows a router to forward DHCP broadcast messages as unicast packets to a DHCP server located in a different network segment.
When a router is configured with a helper address for DHCP, it acts as a DHCP relay agent. The router intercepts the DHCP broadcast messages from the client and encapsulates them into unicast packets. It then forwards these unicast packets to the DHCP server specified by the helper address.
In this scenario, the configuration for the DHCP relay agent (helper address) needs to be present on the router that is closest to the DHCP client. This router is responsible for intercepting the DHCP broadcast messages and forwarding them to the DHCP server. Therefore, the correct answer is B. on the router closest to the client.
The other options are incorrect:
A. The configuration does not reside on the switch trunk interface. Switches are not typically involved in DHCP relay operations. They are primarily responsible for forwarding frames within a local network segment based on MAC addresses.
C. Although the router closest to the server may have routing configurations or access control lists (ACLs) related to DHCP traffic, the actual DHCP relay configuration is not needed on this router. Its purpose is to forward IP packets to the next-hop router towards the destination network.
D. The configuration is not required on every router along the path. Only the router closest to the client needs the DHCP relay configuration to facilitate the DHCP communication between the client and the server. Routers in between do not need this configuration as they only forward IP packets based on routing tables.