| Symptom | Likely Cause | Fix | |---------|--------------|-----| | No Teredo adapter in Device Manager | Disabled via Group Policy or registry | Check HKLM\System\CurrentControlSet\Services\Tcpip6\Parameters\DisabledComponents (should be 0 or not present) | | Adapter stuck "Not ready" | Firewall blocking protocol 41 | Ensure corporate VPN/antivirus allows 41 | | State = offline | Teredo server unreachable | Try alternate server: netsh interface teredo set state server=teredo.remlab.net |