Routes are not being advertised from T1 to the upstream neighbors

Products

• VMware NSX

Issue/Introduction

• Downlinks connected to a Tier-1 are not getting advertised to the connected VRF/T0
• The Tier-1 was originally configured as Distributed Only and had no downlinks (either VLAN or Overlay segments) associated
• Tier-1 was created on VMware NSX 3.0.x or 3.1.x and upgraded to 3.2.x or newer
• Since Tier-1 connected downlinks are not advertised to Tier-0 or physical, north/south communication is not traversing the Tier-1/Tier-0

Full reproduction steps:

1. In VMware NSX 3.0.x or 3.1.x, create a Tier-1 DR Only (connected to VRF/T0 AA (having uplinks) and not having any downlink) 
2. Upgrade to VMware NSX 3.2.x or newer
   1. At this point, the Tier-0 router link port LIF won't have a switch port ID.
3. Enable connected routes advertisement in Tier-1.
4. Add Edge Cluster to Tier-1 (i.e. Change it from Distributed Only to Active-Standby)
5. Create a downlink (segment) and connect it to the Tier-1
6. Check the route for the downlink segment on Tier-1 DR and VRF/T0 SR on edge CLI
7. Advertised route for Tier-1 connected segment will be missing from the Tier-0 forwarding table

Environment

• VMware NSX 3.2.x
• VMware NSX 4.x
• VMware NSX 9.x

Cause

This is a known issue in VMware NSX 3.2.x, 4.x, and 9.x versions.

Resolution

Resolution requires two steps

1. Disconnect the Tier- 1 from the Tier-0.
   1. Log in to the NSX interface
   2. Navigate to Networking → Tier-1 Gateways
   3. Identify the Tier-1 with connected segments that aren't advertising
   4. Click the 3 dots beside the name and click Edit
   5. In the HA Mode ensure Distributed Only is selected
   6. In the Linked Tier-0 Gateways column and click the X beside the Tier-0 name
   7. Click the X beside the Edge Cluster name
   8. Click Save
   9. Click Close Editing
2. Reconnect the Tier- 1 to the Tier-0.
   1. Click the 3 dots beside the name and click Edit
   2. In the HA Mode ensure Active-Standby is selected
   3. In the Linked Tier-0 Gateways column, select the correct Tier-0 Gateway name
   4. Select the correct Edge Cluster name and set desired Failover and Allocation models
   5. Click Save
   6. Click Close Editing