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Zorluk: ZorSNMP Operations, MIBs, Traps, Informs, and Version Differences

A network engineer is troubleshooting event notifications on a Cisco IOS XE router. During periods of heavy WAN link congestion, critical interface state notifications sent to the Network Management System (NMS) are occasionally dropped and lost. The organization mandates that all management notifications must require an explicit application-layer acknowledgment from the NMS to trigger retransmissions if unacknowledged, while ensuring message integrity, authentication, and payload encryption. Which SNMP configuration change satisfies both the operational delivery guarantee and security requirements?

  1. Configure the router to send SNMP Informs rather than Traps, and define the SNMPv3 host with the authPriv security level.Cevap
  2. B
    Reconfigure SNMP notification transport from UDP port 162 to TCP port 161 so that transport-layer windowing and retransmissions automatically guarantee packet delivery.
  3. C
    Maintain SNMP Traps on UDP port 162 and configure an inbound Access Control List on the WAN interface to permit incoming TCP ACK packets from the NMS.
  4. D
    Apply the ip helper-address command on the local router interface pointing to the NMS IP address to relay SNMP trap broadcasts across the WAN.

Cevap

Configure the router to send SNMP Informs rather than Traps, and define the SNMPv3 host with the authPriv security level.
SNMP Traps are unidirectional, unacknowledged UDP messages sent to port 162. Under congested network conditions, lost Traps are never retransmitted. In contrast, SNMP Informs require the receiving Network Management System (NMS) to return an SNMP response back to the agent; if an acknowledgment is not received within a timeout period, the router retransmits the notification. Additionally, SNMPv3 authPriv provides both HMAC authentication and payload encryption (privacy), satisfying the strict security policy.

Adım Adım Çözüm

1
Analyze notification delivery requirements.
Identified that SNMP Traps are unacknowledged UDP messages (fire-and-forget), whereas SNMP Informs require an application-layer SNMP response (acknowledgment) from the NMS and will retransmit if no response is received.
To survive packet drops during WAN congestion, application-layer acknowledgments provided by SNMP Informs are required.
2
Analyze security model requirements.
Identified that authentication (integrity/hashing) plus payload encryption (privacy) corresponds strictly to the SNMPv3 authPriv security level.
authNoPriv provides authentication without encryption, and noAuthNoPriv provides neither authentication nor encryption.
3
Combine operational mechanics and security configuration.
Selected SNMP Informs combined with SNMPv3 authPriv as the correct solution.
This combination satisfies both reliable delivery via retransmissions and strict data confidentiality/integrity.

Anahtar Kavram

SNMP Informs vs Traps operational mechanics and SNMPv3 Security Levels (authPriv)
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Konular

SNMP Operations, MIBs, Traps, Informs, and Version Differences

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