Paths to HUB flap when the spoke/branch edges use a same shared public IP address

Products

• VMware SD-WAN by VeloCloud
• VMware VeloCloud SD-WAN

Issue/Introduction

When more than one spoke edge use the same shared public IP address to build paths to the same HUB edge, an Enterprise administrator may notice the paths from each spoke/branch to the HUB start flapping and it will not get to a STABLE state. This flapping will only occur for the particular paths using this circuit to connect to the same HUB. Other ISP circuits connected to the spoke edges wont be affected

Cause

This issue might be triggered if the below conditions are met:

• Branches/Spoke edges are running 5.1.x or newer and they have a WAN circuit sharing the same public IP address from the ISP. (Example: 2 edges behind the same ISP router or having a common breaking out point to the Internet)
• HUB edge is running software version 5.0.x or older

Resolution

This is an interoperability limitation that can be avoided by always having the HUB edge running the same or newer version than the spokes. This is important when planning upgrades in an Enterprise. It is best practice to upgrade the HUB edge before spoke/branch edges