RT-AX88U w/ Centurylink ONT -- Persistent Disconnects (HELP?)

[Kranbes]

Hi friends,

I'm posting in hopes of getting some help to find out what other troubleshooting may be helpful. I don't have a... strong networking background. I'm happy to make a donation via Venmo to show my gratitude for your time.

I have an Asus RT-AX88U that worked perfectly fine before a recent move. Before, was on comcast, now on CenturyLink fiber in a much larger house.

Set up:
I have the ONT (photo attached) from centurylink installed in our basement; this was installed when we moved in the house. Couldn't find a model number--might need to remove from the wall if it's needed.
We were given a C4000XG router (they call this a modem) from Centurylink, which we swapped out for the RT-AX88U with PPPoE authentication and VLAN tagging per this post.
I have an RT-AC66U set up as an access point upstairs.

Issue:
-Internet keeps disconnecting, every 1-3 days. Hard re-set of RT-AX88U router restores internet
-Troubleshooting: I factory reset router and flashed updated firmware. No improvement. I flashed Merlin firmware. No improvement; only difference is now the WAN light turns red during disconnects. I've also swapped the ethernet cable to the WAN port. Confirmed the ethernet cable is CAT-5e.
-Other notes: Unable to access the router via wireless login or via ethernet login during disconnects. Simply says "Reconnecting to the internet" (photo attached). Ethernet also appears to be inaccessible during disconnects (syslog-2 included a laptop hooked to ethernet to test this).

I have tried to do my homework and read other posts before posting mine:
I'm reading that ASUS routers have issues with ONT fiber set ups? Something about DHCP issues? Some other threads have noted they replaced their router under warranty and issues resolved, while even others talk about using the provided router and set up double NAS (I have no idea how to do that, but could hopefully find some guides). I eventually want to install wired router to TP-link OMADA access points throughout the house for better coverage, so if it's an ASUS issue, I may just pursue that set up sooner than later.

Issue is, I don't know if those people have the same issue I have, because I don't know what my issue is! It seems to be something happening 'after' the ONT, because a hard-reset of the router always fixes the problem -- a reset of the ONT isn't necessary to restore the internet.

I attached systlogs of the last 2 disconnects (syslog-2 was just this morning) below. You'll see that at the time of the disconnect, the dates revert to May 4th for some reason. I see 'errors' and things that don't seem right, but I have no clue how to interpret them. Can anyone help make sense of this?

syslog-1 (June 24th; disconnect around 12:57)​

syslog-2 (June 25th; disconnect around 9 am)​

I really appreciate your expertise and time to help if you can. Like I said, DM me your venmo and I'm happy to send you a thank you tip!

Some photos also attached below, in case they're of value

With gratitude,

-Kranbes

 

[OzarkEdge]

The earlier date in the log is after a reset and before the router gets the current date from the Internet.

Do you reset the firmware and then configure it from scratch?

OE

 

[Kranbes]

Oh okay, that makes sense.

Yes I did reset the firmware. I did a factory reset then re-configured the router.

 

[OzarkEdge]

Oh okay, that makes sense.

Yes I did reset the firmware. I did a factory reset then re-configured the router.

Yes, and don't restore old settings/defaults. Using current firmware, I assume.

Someone here will need to interpret the log entries. Have you always had this issue on the fiber ONT?

Not being able to login to the webUI is odd.

OE

 

[Kranbes]

Yes, and don't restore old settings/defaults. Using current firmware, I assume.

Someone here will need to interpret the log entries. Have you always had this issue on the fiber ONT?

OE

Yes, granted I've only really tested his set up. I pretty much immediately swapped out the provided C4000XG router for the ASUS I had semi-recently bought prior to the move.

I realize IF it's a centurylink issue, or issue with the ONT, I probably will need to set up 'double NAT' and use the C4000XG to receive the initial internet connection then add the ASUS to that. That way, Centurylink will have to come look at the ONT/router if disconnects persist. Just was hoping it was an issue with the ASUS router that I could fix -- I'd prefer not to have to do the double NAT set up, partly because I'd rather not use more devices than necessary, and also because it'll be an uphill climb to figure out how that process works--but if I need to do it, I need to do it.

 

[OzarkEdge]

The fiber cable? entering the bottom of the ONT in pic 832 seems awefully crooked for a FO connection(?). And there *is* a minimum bend radius on fiber.

OE

 

[Kranbes]

The fiber cable? entering the bottom of the ONT in pic 832 seems awefully crooked for a FO connection(?). And there *is* a minimum bend radius on fiber.

OE

It actually attaches to the ONT at an angle, but I just went and tried to ease the bending a bit, so we'll see if that helps! Good thought; thank you

 

[geobernd]

I would go the double NAT route first for a couple of days.
If it still keeps happening it's likely the ONT or Fiber Connection - if it goes away need to closer what happens with the RT-AX88U.

I am on Quantum Fiber (new Name used by Lumen) in a new buildout area with just VLAN 201 - no PPoE and using a RT-AX86U with latest Merlin 386.7 with no issues...

 

[bbunge]

I am on Centurylink fiber and do not have to use PPPoE or vlan. No user ID and password either. My ONT is outside the house in a weather proof enclosure and is powered with a battery backup power supply which is inside the house. I just have CAT5 run to the AX86U and another CAT5 for the phone.

 

[bbunge]

What you have pictured is actually a combo modem, really an ONT and router. Does not have WIFI and that is why they gave you the WIFI "modem."

See this video:

Centurylink really treats its customers like dummies!

 

[Kranbes]

What you have pictured is actually a combo modem, really an ONT and router. Does not have WIFI and that is why they gave you the WIFI "modem."

See this video:

Centurylink really treats its customers like dummies!

I watched that same video to help figure out how to set up my router.

Does anyone know a particular forum member that is helpful with reviewing logs? I feel like I'd like to see what someone much smarter than me thinks is going on. I'm setting up the double NAT in the meantime.