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Difficulty: MediumSNMP Operations, MIBs, Traps, Informs, and Version Differences

A network engineer observes that periodic bandwidth statistics collected from a 10-GigabitEthernet interface on a Cisco router display inaccurate, negative, or wrapping byte counts during peak traffic hours. The Network Management System (NMS) currently uses SNMPv1 to poll standard 32-bit interface counters (`ifInOctets` and `ifOutOctets`). Which SNMP version capability and MIB object group should be deployed to resolve this counter rollover issue?

  1. Migrate to SNMPv2c or SNMPv3 to poll 64-bit High Capacity (HC) counters (`ifHCInOctets` and `ifHCOutOctets`).Answer
  2. B
    Retain SNMPv1 but increase the NMS polling frequency to poll 32-bit counters every 2 seconds.
  3. C
    Configure SNMP Traps on the router to automatically push 32-bit counter values whenever threshold limits are exceeded.
  4. D
    Enable SNMPv3 authPriv security level to automatically encrypt and expand 32-bit counter fields into 64-bit values.

Answer

Migrate to SNMPv2c or SNMPv3 to poll 64-bit High Capacity (HC) counters (`ifHCInOctets` and `ifHCOutOctets`).
High-speed interfaces (such as GigabitEthernet and 10-GigabitEthernet) rapidly roll over standard 32-bit MIB counters (`ifInOctets`/`ifOutOctets`) supported by SNMPv1. SNMPv2c and SNMPv3 introduce IF-MIB 64-bit High Capacity (HC) counters (`ifHCInOctets`/`ifHCOutOctets`), which allow accurate traffic monitoring without counter wrapping.

Step-by-Step Solution

1
Analyze interface speed and counter limits
A 10 Gbps interface transmits up to 1.25×1091.25 \times 10^9 bytes per second. A 32-bit counter caps at 232−1≈4.29×1092^{32} - 1 \approx 4.29 \times 10^9 bytes.
At maximum capacity, a 32-bit counter rolls over approximately every 3.4 seconds (4.29×109/1.25×1094.29 \times 10^9 / 1.25 \times 10^9).
2
Evaluate SNMP version features regarding MIB counter capacity
SNMPv1 is restricted to 32-bit counter objects. SNMPv2c and SNMPv3 introduced 64-bit High Capacity (HC) MIB objects in IF-MIB.
64-bit counters (264−1≈1.84×10192^{64} - 1 \approx 1.84 \times 10^{19}) take hundreds of years to roll over even on 10 Gbps interfaces.
3
Select the correct SNMP configuration update
Upgrading to SNMPv2c or SNMPv3 and requesting `ifHCInOctets` / `ifHCOutOctets` provides accurate bandwidth metrics.
This directly resolves high-speed link counter rollover issues.

Key Concept

64-bit MIB High Capacity (HC) counters introduced in SNMPv2c/SNMPv3 for high-speed interface monitoring
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Topics

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

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