Host devices connected to an access switch on VLAN 15 () are failing to receive automatic IPv4 address assignments. Router R1 serves as the default gateway via its GigabitEthernet0/0.15 subinterface, while the enterprise DHCP server is located at across the WAN backbone. To enable successful DHCP relay operation for hosts on VLAN 15, on which interface must the `ip helper-address 10.1.1.250` command be configured on router R1?
- On subinterface GigabitEthernet0/0.15, because the DHCP relay agent must intercept broadcast DISCOVER requests on the client-facing ingress gateway interface.Cevap
- BOn the WAN interface connected towards the DHCP server, because helper commands direct egress traffic out of the router.
- COn the access switch ports connected to the hosts, because Layer 2 interfaces must rewrite DHCP broadcast frames into unicast frames before forwarding.
- DOn the global configuration mode of router R1 without an interface context, because relay addresses apply router-wide across all active subnets.
Cevap
The helper address command must be configured on subinterface GigabitEthernet0/0.15, which is the client-facing ingress interface serving VLAN 15.
The correct answer specifies configuring the command on subinterface GigabitEthernet0/0.15. A Cisco IOS router acts as a DHCP relay agent by intercepting UDP broadcast traffic (ports 67 and 68) on the incoming client-facing interface, inserting its local interface address into the gateway IP address (giaddr) field of the DHCP packet header, and forwarding the request as a unicast packet to the designated DHCP server IP address.
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Cisco IOS DHCP Relay Agent Interface Placement