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Zorluk: OrtaCommon Ports and Protocols

A network engineer is configuring access control lists on a core switch that routes traffic between an enterprise client VLAN and a server subnet hosting central network services. Endpoints on the client VLAN rely on a local DHCP relay agent embedded in their default gateway to receive IP assignments from the central DHCP server. Which of the following port and transport protocol combinations must be permitted to allow full bidirectional DHCP relay and client-server operation? (Select TWO.)

  1. UDP port 67 for communication directed to the DHCP serverCevap
  2. UDP port 68 for communication directed to the DHCP clientCevap
  3. C
    TCP port 67 for connection-oriented DHCP server requests
  4. D
    UDP port 69 for DHCP lease information transfer

Cevap

The correct port and protocol combinations are UDP port 67 for communication directed to the DHCP server and UDP port 68 for communication directed to the DHCP client.
DHCP operates over UDP using port 67 for destination servers and relay agents, and port 68 for destination clients. Allowing both UDP 67 and UDP 68 ensures that broadcast and unicast DHCP messages (DISCOVER, OFFER, REQUEST, ACK) can traverse network boundaries between client endpoints and central services.

Adım Adım Çözüm

1
Identify the transport protocol used by Dynamic Host Configuration Protocol (DHCP).
DHCP uses User Datagram Protocol (UDP) because initial bootstrapping messages are sent before hosts have configured IP addresses.
TCP requires a valid IP address to complete a three-way handshake, making UDP the necessary choice for host configuration protocols.
2
Determine the destination ports assigned to DHCP server and client roles.
UDP port 67 is utilized by the DHCP server/relay agent, while UDP port 68 is used by the DHCP client.
Both ports must be permitted on intervening firewalls and access lists to allow bidirectional messaging (DISCOVER/REQUEST to server on port 67, and OFFER/ACK to client on port 68).

Anahtar Kavram

DHCP Port and Transport Protocol Specification
Tahmini Süre:1m 30s
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Konular

Common Ports and Protocols

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