Traffic to T1 Segments Drops when Static Route Redistribution is Enabled in NSX

Products

• VMware NSX

Issue/Introduction

In specific NSX environments, enabling the "Static Routes" advertisement/redistribution setting on a Tier-1 (T1) Gateway causes immediate traffic loss to segments attached to that T1. This occurs even if no static routes are currently defined, or if a previously entered static route was invalid. The issue is often isolated to a single T1 while others in the same cluster function normally.

Symptoms:

• Traffic impact for valid static routes on a specific T1 Gateway.
• Log patterns in /var/log/proton/nsxapi.log showing Direction : UNKNOWN for affected networks.

Example log:
Affected networks from route graph are : [{ Network : <IP_ADDRESS>/32, Direction : UNKNOWN, nhToRealExitNextHopMap : ... }]

Environment

VMware NSX-T / NSX 3.x, 4.x, 9.0

Cause

This is caused by stale entry in NSX

Resolution

This issue is resolved in NSX 9.1.

Workaround

If an upgrade is not immediately possible, invoke the Reprocess API for the affected Tier-1 Gateway. This forces the Manager to recompute the route graph from scratch and clear stale in-memory nodes.

API Call:

POST https://<nsx-manager-ip>/policy/api/v1/infra/tier-1s/<tier-1-id>?action=reprocess

Note: This action can be performed without a maintenance window as it triggers a background re-calculation of the routing state.