North-South traffic not working through NSX Edge

Products

• VMware NSX

Issue/Introduction

Pings from a VLAN-connected VM to an overlay connected VM fail consistently. Additionally the following conditions are met:
- there are no firewall rules blocking pings (ICMP)
- performing packet captures reveals that pings from the overlay-connected VM reach the Edge and are successfully forwarded by the NSX Edge (specifically the T0 gateway) towards the physical underlay network
- packet captures also reveal that no ICMP replies are sent from the physical underlay back to the Edge (specifically to the T0 gateway) 

Environment

VMware NSX

Cause

This issue is caused by a misconfiguration in the physical underlay network. 

Resolution

Examine the routing configuration in the physical underlay network directly connected to the NSX Edges (T0 routers). Additionally, examine whether ECMP is correctly configured in the physical routers.

Additional Information

For information on performing packet captures, please see:
How to perform rolling packet captures for vSphere and NSX Analysis