Switch connection Issue with NCC

Hi @PscServices ,

Welcome to the Zyxel Community! When newly registered switches (especially those from "old stock" or previously used environments) fail to connect to the Nebula Control Center (NCC) and remain offline, it is usually due to outdated firmware or localized network settings.

Here are the most effective troubleshooting steps to get your switches connected:

1. Upgrade the Firmware:
   1. Outdated firmware is the most common reason old stock switches fail to connect to Nebula, often due to expired security certificates or protocol changes. Access the switch's local web GUI and manually upgrade them to the latest available firmware version.
2. Check DNS and Internet Resolution:
   1. The switches must be able to resolve and reach Nebula servers. Log into the local GUI, ensure the DNS server is set to a public resolver like 8.8.8.8, and verify if the switch can resolve the Nebula server domain: d.nebula.zyxel.com.
3. Verify System Time (NTP):If the system time on the switch is incorrect, the secure connection (SSL/TLS) to NCC will fail. Ensure NTP is configured and working, or manually correct the time in the local GUI so that certificate handshakes succeed.
4. Open Required Ports:
   1. Ensure your local firewall or gateway is not blocking the ports used by Nebula. The switches require outbound access for:
      1. TCP 4335 & 6667 (Nebula Control Protocol)
      2. TCP 443 (HTTPS)
      3. UDP 123 (NTP Time Sync)

To help us narrow down the issue, could you share:

• The exact product models of both switches?
• Their current firmware versions?
• The status of the LED lights (specifically, is the Locator/Cloud or ALM LED blinking/amber/red)?

Let us know how it goes!