East-West connectivity between VMs connected to two different overlay segments and Tier-1 gateways is down

Products

• VMware NSX

Issue/Introduction

Consider the diagram below -

• VMs are connected to two different overlay segments.
• Each segment is connected to a separate Tier-1 router.
• VM-A and VM-B are unable to connect to each other.

Environment

VMware NSX

Cause

Tier-1 router does not have route advertisement allowed for 'All Connected Segments and Service ports' so Tier-0 routing table does not have route to destination VM network.

Here is an example of Tier-1 connected route learnt in Tier-0. This can be verified from edge CLI.

• Login to edge CLI using 'admin' account and check for logical-routers.
  edge01> get logical-routers
 
• Connect to Tier-0 SR VRF
  edge01> vrf 2
 
• Check all the routes, t1c indicates Tier1-Connected. In non-working state this route would be missing for the destination network.
  
  edge(tier0_sr[2])> get route
Flags: t0c - Tier0-Connected, t0s - Tier0-Static, b - BGP, o - OSPF
t0n - Tier0-NAT, t1s - Tier1-Static, t1c - Tier1-Connected,
t1n: Tier1-NAT, t1l: Tier1-LB VIP, t1ls: Tier1-LB SNAT,
t1d: Tier1-DNS FORWARDER, t1ipsec: Tier1-IPSec, isr: Inter-SR,
ivs: Inter-VRF-Static, > - selected route, * - FIB route

Total number of routes: #

  <snip>
  t1c> * 172.16.#.#/24 [3/0] via 100.64.#.#, linked-297, 6d20h25m

Resolution

Edit Tier-1 configuration and enable route advertisement for 'All Connected Segments and Service ports'.

Additional Information

If you don't want to advertise all connected routes, you can specify which routes to advertise.

Configure Route Advertisement on a Tier-1 Logical Router in Manager Mode