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Zorluk: OrtaDHCP Architecture and Relay Services

An enterprise network contains multiple subnets connected through a core Layer 3 switch. Hosts on VLAN 50 (10.50.0.0/2310.50.0.0/23) fail to acquire IPv4 address leases from the centralized DHCP server located on VLAN 10 (192.168.1.100192.168.1.100). A network technician verifies that the DHCP server is operational and reachable via ICMP from the core switch. Where must the `ip helper-address 192.168.1.100` command be configured on the Layer 3 switch to enable DHCP relay functionality for the client hosts?

  1. On the Switch Virtual Interface (SVI) for VLAN 50Cevap
  2. B
    On the Switch Virtual Interface (SVI) for VLAN 10
  3. C
    In global configuration mode to enable TCP port 67 relaying across all switch interfaces
  4. D
    On the trunk port interface connecting the switch directly to the remote DHCP server

Cevap

The helper address command must be configured on the Switch Virtual Interface (SVI) for VLAN 50.
DHCP relay agents must be configured on the ingress Layer 3 interface (default gateway) of the subnet where client hosts reside. In this scenario, hosts on VLAN 50 send broadcast DHCP requests to their gateway (VLAN 50 SVI). Placing `ip helper-address 192.168.1.100` on the VLAN 50 SVI instructs the switch to convert those broadcast UDP port 67 packets into unicast traffic directed to the remote DHCP server at 192.168.1.100192.168.1.100.

Adım Adım Çözüm

1
Identify the ingress layer 3 boundary for client broadcast traffic.
Client hosts on VLAN 50 transmit DHCPDISCOVER packets as layer 2 broadcasts (255.255.255.255255.255.255.255), which are restricted to VLAN 50.
Layer 3 boundaries block broadcast traffic by default.
2
Determine the interface requiring DHCP relay agent capabilities.
The gateway interface for VLAN 50 (SVI for VLAN 50) must receive the broadcast and convert it to a unicast DHCPDISCOVER packet sent to 192.168.1.100192.168.1.100.
The IP helper address must be enabled on the specific interface receiving the client's local broadcast.
3
Verify protocol and port operation.
The relay agent listens for UDP port 67 client requests on VLAN 50 SVI and populates the `giaddr` field with 10.50.0.110.50.0.1 before unicasting the packet to the server.
The server uses `giaddr` to assign an IP address from the correct pool (10.50.0.0/2310.50.0.0/23).

Anahtar Kavram

DHCP Relay Agent Interface Placement
Tahmini Süre:1m 30s
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Konular

DHCP Architecture and Relay Services

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