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Zorluk: ZorCommon Ports and Protocols

A network technician is troubleshooting an enterprise Network Management System (NMS). The NMS can successfully poll managed routers and switches for status metrics, but it fails to receive automated event notifications, such as link-down alerts, generated directly by the network devices across an internal firewall. Network documentation confirms that outbound traffic from the NMS to managed devices on UDP port 161 is permitted. Which of the following firewall rule modifications will resolve the issue?

  1. Permit inbound traffic from the managed devices to the NMS on UDP port 162.Cevap
  2. B
    Permit inbound traffic from the managed devices to the NMS on TCP port 162.
  3. C
    Permit inbound traffic from the managed devices to the NMS on TCP port 161.
  4. D
    Permit inbound traffic from the managed devices to the NMS on UDP port 514.

Cevap

Permit inbound traffic from the managed devices to the NMS on UDP port 162.
Simple Network Management Protocol (SNMP) uses two separate port numbers: UDP port 161 for agent polling (GET/SET requests initiated by the NMS) and UDP port 162 for trap notifications (spontaneous alerts initiated by managed agent devices to the NMS). Because the NMS can poll but cannot receive alerts, the firewall is blocking agent-initiated traffic destined for UDP port 162 on the management server.

Adım Adım Çözüm

1
Analyze the operational traffic flow described in the scenario.
The NMS polls devices successfully using SNMP GET/SET requests, but spontaneous alert messages (traps/informs) originating from the devices are blocked.
SNMP operates using two distinct communication channels and default port assignments depending on whether the manager or agent initiates communication.
2
Identify the standard protocol and port assigned to SNMP manager polling versus agent traps.
Manager-to-agent polling uses UDP port 161, whereas agent-to-manager asynchronous trap notifications use UDP port 162.
Firewalls must be configured to permit traffic initiated by remote agents destined for the monitoring server's trap receiver service.
3
Select the access list modification that permits asynchronous alerts.
Permitting UDP port 162 inbound from managed network equipment to the management server restores trap logging.
UDP port 162 specifically handles incoming SNMP alert notifications.

Anahtar Kavram

SNMP Ports (UDP 161 for Polling/Agent vs UDP 162 for Traps/NMS Manager)
Tahmini Süre:2m 0s
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Common Ports and Protocols

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