NSX Route Logging causes significant syslog bloat -errorCode="EDG0400418" Failed to add neigh route for next-hop.

Products

• VMware NSX

Issue/Introduction

- The system fails to add a neighbor route for a next-hop in the routing table when a specific IP address is simultaneously defined as both a next-hop and a prefix.
- This is indicated by the following log in syslog:
tname="dp-learning3" level="ERROR" errorCode="EDG0400418" Failed to add neigh route for next-hop
tname="dp-learning3" level="ERROR" errorCode="EDG0400422" Failed to add neigh route (): route of type 0 already exists
- The primary impact is significant syslog bloat, which can consume storage and make log analysis difficult. Continuous > logging of this error at high frequency may also lead to degraded data path performance due to increased CPU cycles spent on log processing.

Environment

NSX 4.2.x

Cause

The syslog repeatedly generates the error errorCode="EDG0400418" Failed to add neigh route for next-hop. This occurs when the Datapath attempts to resolve an ARP entry for an IP address that exists as a /32 prefix in the routing table. This situation typically arises when Fabric Top-of-Rack (TOR) routers advertise directly connected /32 routes (where Edge T0-SR uplinks reside) into BGP while Inter-SR routing is enabled.

Resolution

WORKAROUND STEPS: Modify the Fabric/TOR BGP configuration to prevent the advertisement of directly connected routes for the VLANs where the Edge nodes are connected. Ensure these specific /32 host routes are filtered from BGP updates.

RECOVERY STEPS: Modify the Fabric/TOR BGP configuration to prevent the advertisement of directly connected routes for the VLANs where the Edge nodes are connected. Ensure these specific /32 host routes are filtered from BGP updates.