Have you ever woken up in the morning and opened the Log Center in your Synology DSM and found an error that said: System failed to get External IP? Why does this error appear? What is the direct cause and how do you replicate it? After several tests, I came up with the solution. I’m using External Access “DDNS” for accessing my Synology NAS from anywhere, and everytime I lose connection to my ISP (Internet Service Provider), for whatever reason, this error “System failed to get external IP” comes up in my Log Center.
I live in a small town. On September 24, 2019, we had power failures throughout the town for hours. I have a CyberPower UPS connected to my router together with my Synology NAS. My systems have always remained connected to the UPS and were never turned off, but my Internet service provider control unit went down because it had no power. As a result, my router could no longer connect to the Internet (nor receive its IP address), although it remained on and connected to the UPS. The Synology error message was clear: “System failed to get External IP“, which means the system failed to get the IP number from my Internet Service Provider. When you see this error message in your DSM Log Center, know there’s nothing you can or should do because the system will reconnect automatically to the DDNS service once your ISP is back to normal again. But if you keep having this problem and can’t connect to the Internet in general, contact your ISP.
Once the power returned and my Internet Service Provider control unit was back on, my router finally received the IP address it requested and the Synology “SYSTEM” successfully registered my IP to my Synology DDNS server. If you go online on message boards, a lot of people will tell you there’s a problem with the LAN cable and advise you to change the LAN cable connected to your router. Now, the possibility this error message is caused by a physical issue with the LAN cable is extremely low, like 0.01%. This is a cable that once you put in, you never take it out. For example, I have been using the same LAN cable for over 20 years without any issues.