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Difficulty: MediumCommon Ports and Protocols

A network administrator is setting up a network management system (NMS) to poll status and performance metrics from managed routers and switches across an internal firewall. Which port and transport layer protocol combination must be permitted on the firewall to allow the NMS to issue these polling requests to the managed devices?

  1. UDP port 161Answer
  2. B
    TCP port 161
  3. C
    UDP port 162
  4. D
    TCP port 162

Answer

UDP port 161 must be allowed through the firewall to enable SNMP polling requests from the NMS to managed devices.
Simple Network Management Protocol (SNMP) polling requests initiated by a Network Management System (NMS) target managed agents listening on UDP port 161. Opening UDP port 161 outbound from the NMS to managed devices allows polling traffic to traverse the firewall successfully.

Step-by-Step Solution

1
Identify the protocol required for network device monitoring and polling.
Simple Network Management Protocol (SNMP) is used by an NMS to poll managed devices for status metrics.
SNMP is the standard protocol for centralized network hardware monitoring and metrics collection.
2
Determine the transport protocol and port number for SNMP polling.
SNMP polling requests are sent to managed devices listening on UDP port 161.
UDP is chosen for lower overhead, and well-known port 161 handles request/response agent communications.
3
Differentiate polling operations from asynchronous event notifications.
UDP port 161 receives polling requests, whereas UDP port 162 receives unsolicited SNMP trap/notification events.
Distinguishing between polling (port 161) and traps (port 162) ensures correct directional firewall rule configuration.

Key Concept

SNMP Port and Transport Protocol Differentiation
Estimated Time:1m 0s
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Topics

Common Ports and Protocols

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