Weird Hub3 crash in modem mode with ASUS RT-AX88U

[jrb2021]

Hitting a really weird issue with Hub3 in modem mode, connected to an ASUS RT-AX88U router (with Merlin firmware).  It works absolutely fine, except for one URL which I use to remotely login to my work.  If I go to that URL in the browser, the Hub3 instantly crashes and I get the error "Your ISP's DHCP does not function correctly" in the ASUS dashboard.  After the hub restarts, usually I can go to that page fine, and everything works as normal.

Where it gets weird - it only seems to fail on Tues, Wed and Thurs.  On Mon and Fri it hasn't failed yet (probably jinxing it now) -- but the issue has been happening for weeks and never seems to be an issue Mon or Fri. 

Then today the behaviour changed again -- after the Hub restarted it still wouldn't work at all.  I went to the page and the Hub crashed 4 times in a row.  I left it alone for 30 mins, tried again, and back to working.  Which I don't understand.

I had a Virgin engineer in a week or so ago, and he couldn't figure it out.  He swapped the Hub3 for another one just in case, but while we were experimenting we confirmed that it's only when the Asus router connects to that URL that the problem occurs. After that I went searching on these forums and came across a few similar issues (for example: https://community.virginmedia.com/t5/Networking-and-WiFi/SH3-modem-mode-no-internet-to-ASUS-RT-AC86U... - I tried switch the ASUS DHCP to Continuous mode as suggested, and the problem seemed to go away for a few days, but then came back again).

Today's issue is more worrying (where 3 to 4 restarts didn't fix) because it seems like it's getting worse without me making any changes...

Anyone have any suggestions?

[lotharmat]

No problem!

Replied and tested with my set up - It didn't crash.

It's a weird one!

[conman33158]

Have you tried using Asus stock firmware with the router and not merlin firmware to see if it makes a difference?

[jrb2021]

I haven't.  I will try that out just in case, thanks.

[legacy1]

I did ask that you test with modem mode and a PC no router.

The ASUS could be doing deep inspection on port 53 and crashes with the given URL.

[jrb2021]

So connecting directly to the hub3 doesn't seem to cause the crash when hitting that URL.  Although I can't be sure.  The issue is so damn intermittent, I can't be 100% certain that it just didn't decide to work for the duration of testing.

Downgrading to stock firmware on the ASUS router sort of worked and sort of didn't.  It didn't crash immediately on hitting the URL in the browser, which was positive.  But it then crashed about 2 minutes after I'd gone through the login process and the Citrix remote access app had started up (so different behaviour to the what happens with the Merlin firmware installed).

That's only day 1 after installing.  Will need to see what happens over the next few days to see if it's really any different.  The ASUS router does seem a metric-****-tonne less stable using the stock firmware though.  The WAN link dropped on the ASUS side a couple of times last night (with Merlin it was rock solid).

Given the hub3 seems flakey as a modem, does anyone know whether there any other options?  I think not, but asking the stupid question anyway.  If there are no other options, my next thought was to switch off modem mode, and do a hardwire connection to the hub directly from my windows machine via a couple of powerline adaptors I have lying around.  But not so keen about having two wifi access points sitting next to each other...

[Tudor]

Never ever had trouble with modem mode on a Hub3 or Hub4. Problems usually are bad signal quality.

[conman33158]

The only other option you might try is set up the Virgin Hub in router mode with wifi switched off and use the Asus as an Access Point and see if it does it.

[legacy1]

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@jrb2021 wrote:

So connecting directly to the hub3 doesn't seem to cause the crash when hitting that URL.  Although I can't be sure.  The issue is so damn intermittent, I can't be 100% certain that it just didn't decide to work for the duration of testing.

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Get a extra NIC in the computer and set up ICS to your router as a AP so you can keep testing its likely not a hub problem but the router looking at the URL and crashing it which needs to be fixed. 

This may not crash it but try it

GRC | 's DNS Nameserver Spoofability Test - Router Crash Test