Adding a new VMSS agent pool removes any non-AKS route table entries

[jveski]

What happened:

Added a new agent pool to a VMSS-based AKS cluster.

What you expected to happen:

Manually created entries in the AKS-managed route table to be preserved.

How to reproduce it (as minimally and precisely as possible):

• Create VMSS-based AKS cluster
• Add route to AKS-managed route table
• Create a second agent pool
• Confirm route was removed

[jveski]

Creating this to provide visibility to a known issue.

[jluk]

Acknowledging it is being worked on and in-flight as part of fixes for the multiple nodepool preview.

[jluk]

A fix is actively rolling out for this. The fix is in Canada/Australia thus far, but should be global by Monday at the latest.

[jluk]

Note published for fix released: https://github.com/Azure/AKS/releases/tag/2019-09-23

@jveski I'm going to close this issue assuming the fix is good, but if you still hit this problem after Monday please comment and I can reopen.

Thanks!