Unable to apply Tier-0 Active-Standby configurations to an Edge for set-ups not running BGP with Route-Maps configured

Products

• VMware NSX

Issue/Introduction

Symptoms:
This issue applies to the following scenario:
- Tier-0 Active-Standby configurations
- not running BGP, with static routes only
- with Route-Maps configured
- Customer upgrading to 2.4.x or greenfield deployments running 2.4.x with above configuration will be impacted


During the failed state:
- Tier-0 static routes are not present in the Tier-0 vrf routing table (including the default route)
- what should be Tier-1 learned routes are not present in the Tier-0 vrf routing table
- only connected routes are present in the Tier-0 vrf routing table
- frr errors appear in the Edge /var/log/syslog, including the following:
INFO "Coverting routing proto to frrcfg and pushing it to FRR"
ERROR "No file /config/vmware/edge/frr/frr-additional-config.txt"
ERROR "Unable to push the config to FRR"
- the following file is present: /config/vmware/edge/frr/frrfailedcfg.txt

Environment

VMware NSX-T Data Center
VMware NSX-T Data Center 2.x

Cause

In NSX-T, route maps are configured with several criterion and one of the criteria is called "as-prepend". When no BGP AS is configured, the MP tries to send a config to the Edge with command "set as-path prepend" without specifying the AS numbers. When the Edge Node tries to apply this configuration to the Routing Daemon, it fails resulting in no routes being applied.

Resolution

This is a known issue impacting NSX-T 2.4, 2.4.1, and 2.4.2. 
This issue is resolved in NSX-T 2.5.

Workaround:
One of the following workarounds can be used to workaround the issue:

1. Edit the Tier-0 BGP configuration and add a dummy AS number. (There is no need to enable BGP)
  or
2. Delete the Route-MAP if it's not required or used by the route-redistribution.