Nebula Status Network Tool in uOS: Troubleshoot Cloud Connectivity

Zyxel_Claudia

The Nebula Status tool is an essential network diagnostic feature introduced in uOS 1.30. This tool helps administrators quickly diagnose connectivity issues between their firewall and NCC.

Where to Find the Nebula Status Tool

Navigate to: Maintenance → Diagnostics → Network Tool → Nebula Status

When testing Nebula status, the results will indicate whether your firewall can successfully communicate with NCC.

• Green (Success) – The firewall has full cloud connectivity
• Red (Failure) – Indicates where the failure occurs in the connection process

1. Phase 1 Failure (No Internet Access)

Error Message:Network is unreachable (8.8.8.8)
Possible Causes & Fixes:

• Check if WAN connectivity is down
• Firewall or upstream router may be blocking ICMP (ping)

Reminder: Even if Phase 1 fails, your firewall might still be able to connect to NCC, but the test will flag this issue.

2. Phase 2 Failure (DNS Resolution Issue)

Error Message:Cannot resolve d2.nebula.zyxel.com
Possible Causes & Fixes:

• Incorrect DNS settings on the firewall
• Blocked DNS queries by upstream security policies
• ISP’s DNS server is failing to resolve Nebula’s domain

3. Phase 3 Failure (Nebula Cloud Blocked)

Error Message:TCP ping to d2.nebula.zyxel.com timed out
Possible Causes & Fixes:

• A firewall rule is blocking outbound access to d2.nebula.zyxel.com
• ISP or upstream security policy is preventing connection to Nebula