Fixing Azure Dev Box network connection issues
I recently hit a frustrating issue where my Dev Center network connections started showing errors, and as a result I was not able to connect to my Dev Boxes.
Symptoms
- Dev Center > Network connections shows Failed status on Endpoint connectivity
- Connecting to the Dev Box through the browser or Windows App fails
Current setup
- Route table only had a few specific routes, no 0.0.0.0/0 route
- Firewall had an allow-all network rule for traffic coming from the Dev Box VNET
- NSG rules were default
Root cause
- An automated process disabled the subnet property
defaultOutboundAccess - Announced in Azure updates
- This removes the platform-provided outbound path and breaks public internet egress when no NAT/Firewall is configured, virtual machines and subnets that were created in a virtual network without a defined explicit outbound method were assigned a default public IP address that enables public endpoint connectivity.
What fixed it for me
- Attached a dedicated NAT Gateway to the Dev Box subnet
- In Dev Center, opened the Network Connection and clicked “Update status” on the network connection to run the checks again; endpoint connectivity then passed and outbound worked
- Confirm Dev Box connectivity is restored
