BGP neighbors fail to establish due to IPv4/IPv6 addresses missing on NSX-T edge node interfaces

Products

• VMware NSX

Issue/Introduction

• You recently rebooted an NSX edge node.
• IPv4/IPv6 addresses are missing on edge node interfaces.
• IPv4/IPv6 BGP neighbor relationships will not get established.
• In the Edge node log /var/log/frr/frr.log you see entries similar to the following:
  
  BGP: [EC 33554465] <IPv4-address-1> [FSM] Failure handling event BGP_Start in state Idle, prior events BGP_Start, BGP_Start, fd -1
BGP: [Event] Incoming BGP connection rejected from <IPv4-address-1> since it is not directly connected and TTL is 1
  
  
• In the Edge node log /var/log/syslog we see the following:

nsx-edge-1 bgpd 22005 - - [EC 33554465] <IPv6-address-1> [FSM] Failure handling event BGP_Start in state Idle, prior events BGP_Start, BGP_Start, fd -1
nsx-edge-1 bgpd 22005 - - [EC 33554465] <IPv6-address-2> [FSM] Failure handling event BGP_Start in state Idle, prior events BGP_Start, BGP_Start, fd -1
 

Note: The preceding log excerpts are only examples. Date, time, and environmental variables may vary depending on your environment.

Environment

VMware NSX-T Data Center
VMware NSX

Cause

Routing controller reads interface kernel notifications via netlink socket.
During edge reboot, netlink notifications might get dropped/missed.
This leads to missed configuration on the interfaces in comparison to the kernel.

Resolution

This is a known issue impacting VMware NSX.
In a future release on VMware NSX, as part of the automatic remediation process, the rescanning of interfaces will be implicitly triggered twice by the system.

Workaround:

To recover the missing IPv4/IPv6 addresses, the interfaces can be rescanned using the below command in the edge node CLI as admin user:

Edge> get logical-routers
Edge> vrf <vrf_id of SERVICE_ROUTER_TIER0>
Edge(tier0_sr)> set debug
Edge(tier0_sr)> start rescan interfaces
Edge(tier0_sr)> exit
 

NOTE: For VMware NSX versions prior to 4.1.2, please do not use the workaround on EVPN enabled setups.