T0-Gateway BGP down under excessive testing traffic

Products

• VMware NSX

Issue/Introduction

Symptom:

BGP alarm seen in NSX UI:
In Router xxxx-xxxx-xxxx-xxxx, BGP neighbor xxxx-xxxx-xxxx-xxxx(ip_address) is down.

Traffic originates from a single virtual machine (VM) generating testingTCP SYN packets with a payload size of 1090 bytes.

Heavy traffic (3-4 Gbps) seen in vCenter UI > Edge VM > Monitor > Performance > Advanced > Network

Environment

VMware NSX-T Data Center

Cause

The BGP session instability is triggered by testing traffic exceeding the edge node’s processing capacity.
The high volume of TCP SYN packets (1090-byte payload) floods the edge, causing resource contention and BGP process disruptions.

Resolution

1. Terminate the testing workload on the identified VM.

2.  Confirm BGP neighbor status stabilizes post that.