KillerQueen
New Around Here
Hello,
I have recently been fighting the issue in subject and I want to share my experience in the hope it might help some others. I have read dozens of articles in various forums, trying to work around or fix the problem. It is apparently a frequent problem with various explanations out of which the most credible is a bug in ASUS firmware. It turns out my problem was different.
I have an ASUS RT-AC88U that I recently upgraded from Merlin firmware 386.7_2 to 386.14. I have plenty of wifi devices connected to it as well as a couple of wired computers.
A little bit earlier, my ISP (Telenet Belgium) also has replaced my old cable modem with a new cable router (to which I have no access to settings).
My ASUS router is directly connected to the ISP router and all my devices connect to the ASUS router.
All was perfectly stable before these 2 changes.
Since the upgrade to Merlin 386.14, I discovered regular messages “Your isp dhcp is not functioning properly” in the router management home page, with the WAN port not working anymore.
I believe I already had some episodes of this before upgrading to 386.14 firmware, and was simply power cycling the ASUS router to restore connectivity without noticing the DHCP error message.
But since the move to 386.14 (including factory reset and full manual reconfiguration of the router), I had the problem on a daily basis and even rebooting both routers was not restoring connectivity anymore.
I realised that every time I was switching on my computer (directly wired to the ASUS router) the WAN connection was instantly restored.
Likewise, approximately 15 minutes after switching off that computer, the ASUS router WAN port was going down whether it was configured with DHCP or fixed IP.
It turned out that it was not my computer itself, but rather my Philips 499P screen, that has an onboard docking station with ethernet cable that was responsible of the WAN port going up or down. Once I disconnected the network cable of this screen from the ASUS router, the problem disappeared.
So even though all looked like the problem came from the router, it is apparently some kind of incompatibility between the screen built-in ethernet port and the Asus router ports
I could not find any explanation for this behaviour, and probably never will. I found some posts about people having similar problems with USB-C connected screens.
----------
ASUS-RT88U has an 8 ports switch in addition to the WAN port.
The 8 ports switch is driven by 2 different chips - see here.
My screen was connected to a port attached to the BCM chip. I have not tried yet to connect it to a port attached to the RTL chip.
Maybe it would behave better and avoid bringing the WAN port down (or all ports driven by the BCM chip down... still to confirm too)
My hypothesis is that when the screen is going to sleep, its ethernet port does something that makes the BCM chip hang. And once the screen wakes up (when computer is switched on) it does something the unfreezes the BCM chip and restores the WAN connection.
I'm waiting a few more days to confirm all is stable, and if so I would perform theses additional tests.
EDIT:
I confirm all is back to normal since my screen ethernet port is not connected to the first 4 ports (1-4) of the ASUS router.
I have now reconnected it to port number 8 of the ASUS router, which is managed by an RTL chip.
This chip seems not to suffer from the same issue than the BCM chip. All kept working normally.
Actually, I have nothing else connected on ports 5,6 and 7. So even if this part of the switch is freezing, I do not see it...
Just for the sake of completeness, I'll connect something there and verify if connectivity remains and report a little later.
I have recently been fighting the issue in subject and I want to share my experience in the hope it might help some others. I have read dozens of articles in various forums, trying to work around or fix the problem. It is apparently a frequent problem with various explanations out of which the most credible is a bug in ASUS firmware. It turns out my problem was different.
I have an ASUS RT-AC88U that I recently upgraded from Merlin firmware 386.7_2 to 386.14. I have plenty of wifi devices connected to it as well as a couple of wired computers.
A little bit earlier, my ISP (Telenet Belgium) also has replaced my old cable modem with a new cable router (to which I have no access to settings).
My ASUS router is directly connected to the ISP router and all my devices connect to the ASUS router.
All was perfectly stable before these 2 changes.
Since the upgrade to Merlin 386.14, I discovered regular messages “Your isp dhcp is not functioning properly” in the router management home page, with the WAN port not working anymore.
I believe I already had some episodes of this before upgrading to 386.14 firmware, and was simply power cycling the ASUS router to restore connectivity without noticing the DHCP error message.
But since the move to 386.14 (including factory reset and full manual reconfiguration of the router), I had the problem on a daily basis and even rebooting both routers was not restoring connectivity anymore.
I realised that every time I was switching on my computer (directly wired to the ASUS router) the WAN connection was instantly restored.
Likewise, approximately 15 minutes after switching off that computer, the ASUS router WAN port was going down whether it was configured with DHCP or fixed IP.
It turned out that it was not my computer itself, but rather my Philips 499P screen, that has an onboard docking station with ethernet cable that was responsible of the WAN port going up or down. Once I disconnected the network cable of this screen from the ASUS router, the problem disappeared.
So even though all looked like the problem came from the router, it is apparently some kind of incompatibility between the screen built-in ethernet port and the Asus router ports
I could not find any explanation for this behaviour, and probably never will. I found some posts about people having similar problems with USB-C connected screens.
----------
ASUS-RT88U has an 8 ports switch in addition to the WAN port.
The 8 ports switch is driven by 2 different chips - see here.
My screen was connected to a port attached to the BCM chip. I have not tried yet to connect it to a port attached to the RTL chip.
Maybe it would behave better and avoid bringing the WAN port down (or all ports driven by the BCM chip down... still to confirm too)
My hypothesis is that when the screen is going to sleep, its ethernet port does something that makes the BCM chip hang. And once the screen wakes up (when computer is switched on) it does something the unfreezes the BCM chip and restores the WAN connection.
I'm waiting a few more days to confirm all is stable, and if so I would perform theses additional tests.
EDIT:
I confirm all is back to normal since my screen ethernet port is not connected to the first 4 ports (1-4) of the ASUS router.
I have now reconnected it to port number 8 of the ASUS router, which is managed by an RTL chip.
This chip seems not to suffer from the same issue than the BCM chip. All kept working normally.
Actually, I have nothing else connected on ports 5,6 and 7. So even if this part of the switch is freezing, I do not see it...
Just for the sake of completeness, I'll connect something there and verify if connectivity remains and report a little later.
Last edited:
