SDN Desynchronization Due to Edge Router ASIC Reconfiguration

Summary

On January 26, 2026, AS214503 experienced a network outage caused by Software-Defined Networking (SDN) desynchronization following an ASIC firmware reconfiguration on an edge router. The incident began at 19:00 UTC and was fully resolved at 19:50 UTC, lasting 50 minutes.

The ASIC reconfiguration problem caused portions of the Forwarding Information Base (FIB) to be dropped, resulting in widespread packet loss and network interruptions. Due to the affected ASIC being located on an edge router, the blast radius was significant, impacting North/South traffic flows including Transit and Peering services. Internal East/West traffic and hybrid workloads remained unaffected throughout the incident.

Impact

Primary Cause: ASIC firmware reconfiguration causing FIB desynchronization on edge router
Affected Services: Transit Services, Peering Services (North/South traffic)
Unaffected Services: Internal traffic (East/West), Hybrid workloads
Symptoms:
- Widespread packet loss across external network paths
- Network interruptions affecting Transit and Peering traffic
- Routing anomalies due to missing FIB entries
Customer Impact: External connectivity degradation, packet loss for traffic traversing affected edge router
Geographic Scope: All traffic flows through affected edge router infrastructure

Timeline (All times UTC)

19:00 - ASIC on edge router flashed with new firmware and configuration
19:20 - Network anomalies detected, monitoring systems alert on elevated packet loss and routing irregularities
19:30 - Investigation initiated, FIB desynchronization identified as root cause, mitigation efforts begin
19:40 - Initial recovery achieved, routes successfully re-added to FIB and propagating correctly across the network
19:50 - Incident resolved, network confirmed stable, all Transit and Peering services operating normally

Root Cause

Primary Cause: The ASIC firmware reconfiguration process on the edge router caused a desynchronization between the SDN controller state and the hardware FIB. During the firmware flash operation, portions of the FIB were dropped, resulting in missing forwarding entries for critical network routes.

Contributing Factors:

ASIC firmware update process did not preserve FIB state during reconfiguration
Lack of pre-flash FIB validation and backup procedures
Missing automated FIB synchronization verification after firmware operations
Edge router location amplified impact due to high traffic volume and critical network position

Technical Details: When the ASIC was flashed with new firmware and configuration, the hardware FIB entries were partially cleared. The SDN controller maintained its route state, but the edge router ASIC no longer had the corresponding forwarding entries, causing packets destined for those routes to be dropped. This desynchronization persisted until routes were manually re-added and properly propagated to the hardware FIB.

Resolution

Immediate Actions:

Identified FIB desynchronization as root cause at 19:30 UTC
Initiated route re-injection from SDN controller to affected ASIC
Verified route propagation and FIB table consistency
Monitored packet loss metrics for recovery confirmation

Recovery Actions:

Routes successfully re-added to FIB at 19:40 UTC
Verified proper route propagation across network infrastructure
Confirmed Transit and Peering services restored to normal operation
Monitored network stability through 19:50 UTC before declaring incident resolved

Prevention Measures

Firmware Baking Process: Added FIB validation steps to firmware baking process to verify FIB integrity before and after ASIC reconfiguration
Pre-Flash Validation: Implemented FIB state backup and validation procedures prior to any ASIC firmware operations
Post-Flash Verification: Added automated FIB synchronization checks following firmware updates to detect desynchronization immediately
Change Management: Updated ASIC firmware update procedures to include FIB preservation requirements
Monitoring Enhancement: Implemented real-time FIB consistency monitoring between SDN controller state and hardware tables
Rollback Procedures: Established rapid FIB restoration procedures for future firmware-related incidents

Incident resolved. All Transit and Peering services operating normally with enhanced FIB validation in firmware baking process.