Lima Yankee
New Around Here
I have had a weird issue with my RT-AC68U router and wondering if anyone has any idea what the cause might be...
My setup is as follows:
Coaxial Cable -> Arris CM8200 modem (NTD) -> ASUS RT-AC68U running Merlin 386.14_2
I woke up yesterday morning to find that my home wifi network had no internet access.
The problem was not with the ISP or modem – status lights on cable modem all looked ok, and was able to access the internet by connecting a PC directly to the modem's ethernet port.
The problem appeared to be that the RT-AC68U router was unable to obtain a WAN IP address from the ISP. My ISP supports both PPoE and IPoE – when set to IPoE I got the error "Your ISP's DHCP does not function properly" and when set to PPoE it said "Disconnected" and was showing one of the two WAN IP addresses (presumably the local IP) as 0.0.0.0.
After a lot of mucking around (factory reset, reverting from Merlin (386.14_2) to stock firmware (3.0.0.4.386_51733), swapping out the ethernet cables in case they were faulty, trying a different router) I determined the problem only occurred when my Dell WD19S USB-C docking station was connected to the router's LAN port. The docking station had a Windows 11 laptop connected to it, but the laptop was powered off (hibernated, not sleeping). When I unplugged the ethernet cable from the docking station, the router would obtain a WAN IP and connect to the internet within about 30 seconds, and when I plugged the docking station back in the router would lose its IP and drop the WAN connection within about 30 seconds. Same thing happened when I disconnected and reconnected the docking station's USB-C cable to the laptop (which I think causes the ethernet port on the dock to power up/down).
I also noticed that whenever the issue was occurring, the PC I was working from was unable to get an IP address from the router via ethernet (I had to connect to the router via Wifi).
At this point it was 2am so I decided to give up for the night and continue investigating the next day, and of course, today I'm unable to replicate the problem (i.e. everything works fine now).
This all seems fairly bizarre – does anyone have any idea why plugging a device into a router's LAN port might cause the WAN connection to drop or lose its IP address? Any why the issue might spontaneously resolve itself?
Everything seems to be working again (for now) but would just really like to know what went wrong!
In anticipation of questions:
- Yes, I had released the IP address on my PC (i.e. run ipconfig /release and ipconfig /release6) before disconnecting it from the modem, so that shouldn't have been the reason the router was unable to obtain a WAN IP.
- No, I did not have Dual WAN enabled, i.e. the ethernet port the dock was plugged into was not configured as a WAN port.
- The laptop was definitely powered off. I've run a malware scan on it just in case and it comes up clean.
- No, I didn't test plugging the dock into different LAN ports on the router, or plugging a different laptop into the dock. (I was going to try that today, but the problem seems to have disappeared.)
- No, I didn't try replicating the issue with a different router. (Again, I was going to try that today.) I did test with a different router during troubleshooting, but I didn't have anything plugged into its LAN ports.
- No, I had not made any recent configuration changes to the router or any devices on my network.
Thanks in advance!
My setup is as follows:
Coaxial Cable -> Arris CM8200 modem (NTD) -> ASUS RT-AC68U running Merlin 386.14_2
I woke up yesterday morning to find that my home wifi network had no internet access.
The problem was not with the ISP or modem – status lights on cable modem all looked ok, and was able to access the internet by connecting a PC directly to the modem's ethernet port.
The problem appeared to be that the RT-AC68U router was unable to obtain a WAN IP address from the ISP. My ISP supports both PPoE and IPoE – when set to IPoE I got the error "Your ISP's DHCP does not function properly" and when set to PPoE it said "Disconnected" and was showing one of the two WAN IP addresses (presumably the local IP) as 0.0.0.0.
After a lot of mucking around (factory reset, reverting from Merlin (386.14_2) to stock firmware (3.0.0.4.386_51733), swapping out the ethernet cables in case they were faulty, trying a different router) I determined the problem only occurred when my Dell WD19S USB-C docking station was connected to the router's LAN port. The docking station had a Windows 11 laptop connected to it, but the laptop was powered off (hibernated, not sleeping). When I unplugged the ethernet cable from the docking station, the router would obtain a WAN IP and connect to the internet within about 30 seconds, and when I plugged the docking station back in the router would lose its IP and drop the WAN connection within about 30 seconds. Same thing happened when I disconnected and reconnected the docking station's USB-C cable to the laptop (which I think causes the ethernet port on the dock to power up/down).
I also noticed that whenever the issue was occurring, the PC I was working from was unable to get an IP address from the router via ethernet (I had to connect to the router via Wifi).
At this point it was 2am so I decided to give up for the night and continue investigating the next day, and of course, today I'm unable to replicate the problem (i.e. everything works fine now).
This all seems fairly bizarre – does anyone have any idea why plugging a device into a router's LAN port might cause the WAN connection to drop or lose its IP address? Any why the issue might spontaneously resolve itself?
Everything seems to be working again (for now) but would just really like to know what went wrong!
In anticipation of questions:
- Yes, I had released the IP address on my PC (i.e. run ipconfig /release and ipconfig /release6) before disconnecting it from the modem, so that shouldn't have been the reason the router was unable to obtain a WAN IP.
- No, I did not have Dual WAN enabled, i.e. the ethernet port the dock was plugged into was not configured as a WAN port.
- The laptop was definitely powered off. I've run a malware scan on it just in case and it comes up clean.
- No, I didn't test plugging the dock into different LAN ports on the router, or plugging a different laptop into the dock. (I was going to try that today, but the problem seems to have disappeared.)
- No, I didn't try replicating the issue with a different router. (Again, I was going to try that today.) I did test with a different router during troubleshooting, but I didn't have anything plugged into its LAN ports.
- No, I had not made any recent configuration changes to the router or any devices on my network.
Thanks in advance!
