Extended convergence time seen when NSX-based OSPF area border router with highest IP address is shut down or rebooted

Products

• VMware NSX

Issue/Introduction

Symptoms:

• If an NSSA area border router which does not have the highest IP address is shut down or rebooted, traffic converges rapidly to another path.
• If an NSSA area border router with the highest IP address is shut down or rebooted, a multi-minute re-convergence time is seen. The OSPF process can be cleared manually to reduce the convergence time.

Environment

VMware NSX for vSphere 6.1.x
VMware NSX for vSphere 6.0.x

Cause

VMware NSX for vSphere 6.x always assigns Type 7 to Type 5 translation to the router with the highest router ID. Generally, the ABR has the highest router ID.

NSX does not offer a configurable option to specify the translator. This diagram illustrates the routing design which leads to the issues described in the Symptom section.

Resolution

To avoid running into this convergence issue, do not configure the Edge Services Gateway (ESG) as ABR in this ECMP topology.

Additional Information