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Zorluk: ZorDHCP Server, Client, and Relay Agent Operation and Configuration

A network engineer is configuring a Cisco IOS router to relay DHCP requests from clients residing in VLAN 10 (192.168.10.0/24192.168.10.0/24) and VLAN 20 (192.168.20.0/24192.168.20.0/24) to a centralized DHCP server at 10.10.10.1010.10.10.10 located off uplink interface GigabitEthernet 0/1. Which two statements correctly describe the required interface configuration and relay agent behavior on the router?

  1. The ip helper-address 10.10.10.10 command must be applied directly under subinterfaces GigabitEthernet 0/0.10 and GigabitEthernet 0/0.20.Cevap
  2. The router replaces the incoming DHCP Discover broadcast with a unicast packet to 10.10.10.10 and inserts the subinterface IP address into the Gateway IP Address (giaddr) field.Cevap
  3. C
    The ip helper-address 10.10.10.10 command must be applied on the egress interface GigabitEthernet 0/1 facing the centralized server.
  4. D
    The router floods the original Layer 2 broadcast DHCP Discover frame unchanged across all active router interfaces to reach the server.

Cevap

The ip helper-address command must be configured on the incoming client-facing interfaces (GigabitEthernet 0/0.10 and GigabitEthernet 0/0.20), and the router converts the incoming DHCP broadcast into a unicast frame while inserting its local interface IP into the gateway IP address (giaddr) field.
DHCP relay agents must be configured on the interface receiving the client DHCP broadcast requests (the incoming subinterfaces for VLAN 10 and VLAN 20). When the router intercepts the broadcast DHCP Discover packet, it encapsulates the payload into a unicast IP packet destined for the configured helper address (10.10.10.10) and places the receiving interface IP address into the Relay Agent IP Address (giaddr) field so the DHCP server can identify the correct subnet pool.

Adım Adım Çözüm

1
Identify client ingress interfaces
DHCP clients broadcast on their local subinterfaces (GigabitEthernet 0/0.10 and GigabitEthernet 0/0.20).
The router must listen for UDP port 67 broadcast messages on the interfaces connected to the clients.
2
Apply helper address configuration
Configure 'ip helper-address 10.10.10.10' under GigabitEthernet 0/0.10 and GigabitEthernet 0/0.20.
This instructs Cisco IOS to intercept incoming DHCP broadcasts on those specific client segments.
3
Analyze Relay Agent packet transformation
Broadcast Discover packets are unicast to 10.10.10.10, and the giaddr field is populated with the subinterface's IP address.
The giaddr field tells the remote DHCP server which IP address pool scope to select from for lease assignment.

Anahtar Kavram

DHCP Relay Agent Operation and Configuration
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Konular

DHCP Server, Client, and Relay Agent Operation and Configuration

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