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300-410 · Question #86

Refer the exhibit. Which action resolves intermittent connectivity observed with the SNMP trap packets?

The correct answer is B. Increase the CIR of the mgmt class map. Intermittent connectivity for SNMP trap packets, likely due to CoPP, can be resolved by increasing the allocated bandwidth.

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Question

Refer the exhibit. Which action resolves intermittent connectivity observed with the SNMP trap packets?

Exhibit

300-410 question #86 exhibit

Options

  • ADecrease the committed burst Size of the mgmt class map
  • BIncrease the CIR of the mgmt class map
  • CAdd a new class map to match TCP traffic
  • DAdd one new entry in the ACL 120 to permit the UDP port 161

How the community answered

(36 responses)
  • A
    3% (1)
  • B
    81% (29)
  • C
    6% (2)
  • D
    11% (4)

Why each option

Intermittent connectivity for SNMP trap packets, likely due to CoPP, can be resolved by increasing the allocated bandwidth.

ADecrease the committed burst Size of the mgmt class map

Decreasing the committed burst size would make the policing even stricter, causing more drops and exacerbating the intermittent connectivity issue.

BIncrease the CIR of the mgmt class mapCorrect

Intermittent connectivity for SNMP trap packets suggests that the Committed Information Rate (CIR) for the 'mgmt' class map, which likely handles SNMP traffic, is set too low. Increasing the CIR allows the router to process a higher volume of legitimate SNMP trap packets without dropping them due to policing, thus resolving the intermittent connectivity issue.

CAdd a new class map to match TCP traffic

SNMP traps use UDP, not TCP, so adding a class map for TCP traffic would have no effect on SNMP trap packets.

DAdd one new entry in the ACL 120 to permit the UDP port 161

SNMP traps typically use UDP port 162 for sending traps, not 161 (which is for SNMP queries); even if the port were correct, an ACL blocking would cause consistent, not intermittent, connectivity issues, and this is a CoPP-style question.

Concept tested: Control Plane Policing (CoPP) rate limiting

Source: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/sec_data_copp/configuration/xe-16/sec-data-copp-xe-16-book/sec-copp-policer-data-plane.html

Topics

#QoS#SNMP#Traffic Policing#Troubleshooting

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