How to Fix Static Route Failover Issues in NSX-T Tier-0 Gateway with Active-Standby Edge Nodes

Products

• VMware NSX

Issue/Introduction

• A Tier-0 gateway is configured with an active-standby Edge cluster.
• The Edge nodes present on the Tier-0 gateway for example, Edge node A (active) and Edge node B (standby).
• Static route is configured along with Administrative Distance (AD) to set the priority for the traffic being routed via the edge nodes.
• For Example:
  
  • Static route to Active Edge node A, has AD 1.
  • Static route to Standby Edge node B, has AD 10.
  • 

• Traffic will be routed via Edge node A due to the lower AD value configured.
• A failover of edge nodes from active to standby is performed, making node B as the active node and Node A as the standby node.
• After the failover, the traffic was still routed through edge node A rather than node B.
• Traffic will continue to route through the standby node A, unless the static routes configuration is modified manually.
• After reconfiguring the static routes and corresponding AD to below, traffic gets routed through Node B.
  
  • Static route to standby Edge node A, has AD 10.
  • Static route to active Edge node B, has AD 1.
• The above change has to be implemented manually every time a failover of edge nodes is performed changing the active and standby edge nodes.

Environment

VMware NSX

Cause

• This is an expected behavior due to the configuration of the static routes and AD.
• Even after the failover, due to the low value of AD configured with the standby node, the route preferred would be of the previous active node.
• Reconfiguring the static routes on the neighbor will update the preferred route to the new active Edge node.

Resolution

To prevent manually changing the AD values for the routes across the Tier-0 gateways, whenever there is a failover of edge nodes, a HA cluster configuration can be implemented or static route BFD can be utilized.

• For configuring the HA VIP for the static service interfaces, please refer article: HA VIP Configuration on Tier-0 gateway.
• For configuring the static route BFD, please refer article: Configure NSX BFD