@1TRUTH1GOD 

Even if a TP-Link Deco guest network is disabled via the app, devices that were previously connected may still be able to be pinged. The most effective solution is to reboot your entire Deco system after turning off the guest network. 

Why you can still ping devices

• Changes require a system reboot: For some Deco models and firmware versions, simply turning off the guest network in the app does not immediately disable all associated network services. A full system reboot is required to clear these settings completely and ensure the network is no longer active.
• Deco is running in Access Point (AP) mode: If your Deco system is running in AP mode, its guest network functionality is different. Unless a specific "Isolated From Main Network" switch is enabled, guest network devices may still be able to communicate with the main network. If you then disable the guest network, this isolation rule may not apply to any lingering connections.
• Devices have a static IP: If a device was previously connected to the guest network and assigned a static IP address, it might still retain that IP even after the network is disabled. If the device can still communicate with the network (for example, through a wired connection), it can still be pinged.
• The device is on the main network: The device you are pinging might have automatically reconnected to your main Wi-Fi network after the guest network was shut off. This is likely if the main network has the same SSID or is a known connection for that device. 

Steps to resolve the issue

1. Reboot your entire Deco system:
   1. Open the Deco app.
   2. Navigate to More > System > Reboot to restart your entire Deco mesh system.
   3. This is the most reliable method for ensuring that all services, including the guest network, are properly shut down.
2. Manually toggle and reboot again:
   1. In the Deco app, re-enable the guest network.
   2. Wait a few moments, then turn it off again.
   3. Perform a full system reboot as described above. This can sometimes clear stubborn settings.
3. Check for firmware updates:
   1. Ensure your Deco units are running the latest firmware, which may contain bug fixes related to network isolation and guest access.
   2. In the Deco app, go to More > System > Update Deco to check for updates.
4. Confirm the Deco operation mode:
   1. If your Deco is set to Access Point mode, go to the Guest Network settings in the app.
   2. Make sure the "Allow Local Access" toggle is set to OFF to prevent devices on the guest network from accessing devices on the main network.