An architect has just deployed a new NSX Edge cluster in a VMware Cloud Foundation (VCF) fleet. The BGP peer between the NSX Tier-0 gateway and the…

The scenario describes a stable BGP session between the NSX Tier-0 gateway and the Top-of-Rack (ToR) router, which confirms that network connectivity and basic BGP parameters are correct. However, the Tier-0 is not receiving a default route (0.0.0.0/0), which is essential for routing traffic to external networks like the internet.

For the Tier-0 gateway to learn the default route via BGP, the peer router (the ToR) must be explicitly configured to advertise it. If the ToR router does not have a default route in its own routing table or is not configured with a policy to originate and advertise one to the NSX Tier-0 BGP neighbor, the route will not be sent, directly causing the issue described.

A. Missing BGP communities on the ToR would affect route filtering or policy application but would not inherently prevent the advertisement of a default route.

B. This describes the reverse traffic flow. The ToR receiving a default route from the Tier-0 is for inbound traffic, not for workload outbound internet access.

C. A route limit issue is improbable because the BGP session is described as "up and stable." Hitting a route limit typically causes the session to flap or reset.

1. VMware NSX-T Data Center Design Guide: In the section "Tier-0 Gateway Design

" the guide details the BGP peering relationship with physical routers. It establishes that for north-south connectivity

the physical network infrastructure is responsible for advertising external network reachability (such as a default route) to the NSX Tier-0 gateways. The absence of this advertisement from the physical router is a common configuration error. (Reference: VMware NSX-T Data Center Product Documentation

NSX-T Data Center Design Guide

Chapter 5: Tier-0 Gateway Design).

2. VMware Cloud Foundation Architecture and Design Guide: This guide specifies the physical network requirements for a VCF deployment. In the "NSX Network Design" section

it mandates that upstream physical routers (ToRs) must be configured for BGP peering with the NSX Edge nodes to exchange routing information. This explicitly includes the advertisement of a default route from the physical network to the NSX Tier-0 for external access. (Reference: VMware Cloud Foundation Documentation

Architecture and Design Guide

Section: NSX-T Data Center Design for VMware Cloud Foundation).

3. VMware NSX Administration Guide: The guide's section on "Configure BGP on a Tier-0 Gateway" explains the process of setting up BGP neighbors and route filters. It implicitly relies on the BGP peer (the ToR) being correctly configured to send the desired routes. Verifying received routes is a standard troubleshooting step

and an empty or incomplete list of received routes points to a configuration issue on the advertising peer. (Reference: VMware NSX Product Documentation

NSX Administration Guide

Chapter: Tier-0 Gateways

Section: Configure BGP).