Ferritaas Incident Intelligence
Defect Intelligence Report Bug 0898205 Severity: High (P2)

SNMPv3 Engine ID Conflict on HA Failover Triggering Monitoring Blackout

Following FortiGate HA cluster failovers, secondary nodes retain independent hardware EngineIDs and uncoordinated boot counters, causing Network Management Systems (NMS) to drop polling sessions with RFC 3414 USM security errors.

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⏱️ Est. Triage: 6–8 mins | Automated CLI Available

Technical Root Cause Analysis

Under standard FortiOS SNMPv3 implementations, the snmpd daemon automatically derives its snmpEngineID octet string from the chassis enterprise prefix and physical hardware serial number. In an active-passive FortiGate Clustering Protocol (FGCP) cluster, the primary unit processes all SNMP traffic directed to the cluster virtual management IP. Remote NMS servers establish cryptographic USM time windows by caching the primary unit's snmpEngineID, snmpEngineBoots, and snmpEngineTime.

When an HA failover triggers (such as during link failure or planned unit restart), the standby node assumes the cluster virtual IP. However, under Bug 0898205, the FGCP heartbeat synchronization daemon fails to replicate the active SNMPv3 engine state to the secondary unit. When the NMS transmits authenticated SNMPv3 GET or WALK queries to the newly promoted primary, the secondary's snmpd rejects the packets due to an unknown EngineID or increments usmStatsNotInTimeWindows. This results in an immediate, total telemetry blackout across SolarWinds, Datadog, PRTG, and Prometheus collectors.

[snmpd] incoming SNMPv3 packet from 10.200.1.50:51844 on port1 (cluster VIP) [snmpd] usm: engineID mismatch: received 800004fb0300090f1234aa, local 800004fb0300090f5678bb [snmpd] usm: usmStatsNotInTimeWindows incremented: msgBoots=14, localBoots=2, msgTime=189423, localTime=412 [snmpd] security error: usmStatsUnknownEngineIDs: 1 [snmpd] packet dropped: authentication failure or out of sync window (RFC 3414 drop)

Affected Firmware & Blast Radius Matrix

FortiOS Branch Vulnerable Builds Confirmed Clean Build Status & Workaround
FortiOS 7.2 7.2.2 – 7.2.7 7.2.8+ Set static cluster engine-id
FortiOS 7.4 7.4.0 – 7.4.3 7.4.4+ Apply manual engine-id-type hex
FortiOS 7.0 Not Affected 7.0.x Branch Clean Legacy engine state handling prevents desync

Platform Impact: Affects enterprise HA clusters across FortiGate 100F, 200F, 400F, 600F, and 1000F models polled via SNMPv3 authPriv or authNoPriv by automated monitoring platforms.

Step 01: Free Verification CLI (Safe Read-Only)

Run these diagnostic commands to inspect your active SNMPv3 engine identity and monitor live packet rejections on the standby or newly promoted primary unit:

Diagnostic Commands

# 1. View local SNMP engine info, boot count, and uptime
diagnose snmp sysinfo

# 2. Run real-time SNMP daemon debug to catch USM authentication failures
diagnose debug application snmpd -1
diagnose debug enable

# 3. Verify HA cluster member serial numbers and failover status
diagnose sys ha status

Remediation & Workaround Steps (Teaser Preview)

Follow the complete step-by-step remediation guide in the Ferrite interactive platform:

Step 02: Identify Secondary Unit Engine ID & Boot Time Skew

Compare SNMPv3 parameters between primary and secondary members via dedicated HA management interfaces.

🔒 Interactive CLI Available in Ferrite Runbook #06

Step 03: Configure Global Static EngineID Override

Apply a cluster-wide deterministic EngineID under config system snmp sysinfo to decouple from hardware serials.

🔒 Interactive CLI Available in Ferrite Runbook #06

Step 04: Gracefully Reset snmpd Daemons without Packet Loss

Cycle the SNMP daemon to flush out-of-sync boot counters and re-establish NMS polling immediately.

🔒 Interactive CLI Available in Ferrite Runbook #06
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Frequently Asked Questions

Why does restarting the NMS service temporarily fix the polling?

Restarting the NMS clears its local USM credential and time cache. The NMS re-discovers the new primary unit's EngineID and re-negotiates boot counters from scratch, but it will break again upon the next failover.

Does setting a static EngineID require an outage or reboot?

No. Configuring set engine-id-type custom under config system snmp sysinfo takes effect immediately without interrupting firewall data plane traffic or restarting the cluster.

Are SNMPv2c communities impacted by this issue?

No. SNMPv2c uses simple community string validation without cryptographic engine IDs or boot counter time-window checks, so it is immune to Bug 0898205.