Router not getting internet back after WAN drop

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ChokeOnThatCausality

New Around Here
Hi Everyone,

I have an annoying probem, that becomes somewhat more annoying when working from home. In short, whenever my WAN connection blips (goes down for any amount of time), when it comes back up, my router never recognizes that it has an internet connection again (says 'disconnected' in the webui). When 'disconnected' in the router webui, I can still connect to the webui on the modem and know that the internet from the modem works generally (will be explained below).

This problem has been intermittent for years, but has recently become worse. I was initially running an AC68U connected to a Rogers (only mildly important) cable modem, but I don't remember what it was. I went though several asus-merlin firmware versions with no change, then finally ditched Rogers for a different ISP (still using the Rogers infrastructure). With my new ISP I am using a Hitron CDA3 modem, and that setup worked quite well for about 2 years before the problem started cropping up again.

In order to troubleshoot I put a gigabit switch between my modem and my router so I could check whether I had internet while my router was still connected and showing 'disconnected'. I discovered that I did in fact have internet, and rebooting either the cable modem OR the router restored the connection, though anything connected directly to the switch got its connection back automatically without issue. When the router was connected directly to the modem I was able to just unplug and replug the network cable between the two to restore the connection.

I started to suspect that maybe my router was failing (pretty old at this point) so I replaced it with an RT-AX88U (running firmware version 386.1_2). This didn't solve the problem.

I know that my ISP (or rather Rogers) has a stability issue that is causing my modem to drop, but I would expect my connection to come back as soon as the internet is back up.

At this point I'm stuck. Any hints at what to look for in the logs or elsewhere would be appreciated. I've set the log level to 'debug' so can hopefully start digging out any relevant information when my connection drop again.

Thanks for looking.
 

HellDiver

Regular Contributor
It's usually the WAN DHCP lease not renewing, and it's the ISP's issue. I have the same problem here, where I use the ISP's cable router in modem mode. If I reboot my main Asus, it'll sometimes not get a DHCP lease off the modem. I then have to reboot the modem (which takes nearly 10 minutes while it messes about with the VoIP etc) and then everything starts up again.
 

MvW

Senior Member
Maybe this script by @Martineau can help? It's more a workaround than a solution, but still...

 
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ChokeOnThatCausality

New Around Here
Thanks for the suggestions so far! I changed the 'DHCP query frequency' to 'continuous'. I admittedly have no idea if that's even applicable but I'll see how it goes. Then I'll try the second.
 

Rassal

Regular Contributor
Thanks for the suggestions so far! I changed the 'DHCP query frequency' to 'continuous'. I admittedly have no idea if that's even applicable but I'll see how it goes. Then I'll try the second.
I second on that suggestion, that is how i got my router to get working when WAN drops... not so often, but this way, it comes back for me.
 

meistadieb

Occasional Visitor
It's usually the WAN DHCP lease not renewing, and it's the ISP's issue. I have the same problem here, where I use the ISP's cable router in modem mode. If I reboot my main Asus, it'll sometimes not get a DHCP lease off the modem. I then have to reboot the modem (which takes nearly 10 minutes while it messes about with the VoIP etc) and then everything starts up again.
I think you mix two things up. The WAN IP from your ISP is independent of the IP your modem is delivering. My network is running in a 172. network provided by my Asus. My modem is running a DHCP with a 192. network. I assigned a fixed IP from that network to my router. The WAN IP displayed for the internet connection is completely independent of 172 or 192. If your router is getting no IP from your modem I doubt it is a ISP problem.
 

ChokeOnThatCausality

New Around Here
Confirmed that the change I made DIDN'T work. I can easily replicate by unplugging the coax from the modem then plugging it back in. The router never gets a WAN IP again without something being rebooted. If I plug something into a different port on the switch, the internet is working... just not for the router.
 

MvW

Senior Member
Then I suggest you use ChkWAN.sh as mentioned before. It's not ideal, but at least your WAN status will be checked continuously and your router rebooted if needed. Do you get an IP assigned immediately after a reboot?
 

ColinTaylor

Part of the Furniture
In order to troubleshoot I put a gigabit switch between my modem and my router so I could check whether I had internet while my router was still connected and showing 'disconnected'. I discovered that I did in fact have internet, and rebooting either the cable modem OR the router restored the connection, though anything connected directly to the switch got its connection back automatically without issue. When the router was connected directly to the modem I was able to just unplug and replug the network cable between the two to restore the connection.
I'm not sure what exactly you've got setup here. There should only be one device connected to the modem, either directly or via a switch. You should never have more than one unless your ISP line is provisioned for multiple WAN connections (usually for an additional cost, and assuming the modem supports it).
 

ChokeOnThatCausality

New Around Here
I'm not sure what exactly you've got setup here. There should only be one device connected to the modem, either directly or via a switch. You should never have more than one unless your ISP line is provisioned for multiple WAN connections (usually for an additional cost, and assuming the modem supports it).
My ISP is surprisingly happy to hand out more than one WAN IP. I don't really get it either, but it's working for me right now for testing at least.

I've set up the monitoring script, and now I'll wait and see how it goes. I've initially set it up just to restart the WAN interface, but failing that I'll make it reboot the router.
 

xlr

New Around Here
Hi!
Any feedback on this script? :) Thank you!
 

ChokeOnThatCausality

New Around Here
So far restarting the WAN interface hasn't worked. Did give me a different message though... my modem is not handing out an IP via DHCP. I'll update to force a reboot and report back on how that goes.
 

MrRederick

Occasional Visitor
I have a similar, recurring issue, and will give the CheckWAN script a try. I'm a UK Virgin Media customer, and occasionally (~once a week) the ASUS will stay "No internet", but I can still be pinged on the IP assigned from the outside (I use thinkbroadband.com ping monitor), and my corporate VPN stays connected.

The fix I use is not a full reboot of either the Asus or the cable modem, but just to log in to the Asus web page, click the internet circle, and then set "internet connection" to OFF. Count to 5, and set it to on. That solves the problem, and I assume forces the Asus to restart the DHCP client.

If anyone knows how I can increase logging, or set up a "watchdog" that does this automatically?? I will look at the Chk-WAN now.
 

MrRederick

Occasional Visitor
Just curios, are people experiencing this also have Adaptive QoS turned on? As noted in the wiki here, that might be a factor in WAN DHCP not renewing. YMMV.
QoS is not enabled, of any type. My older (much slower) ISP used PPPoE, and I never had a problem until I switched to cable where the WAN is DHCP. I suspect the fault is in the cable provider not meeting the correct RFC specifications for DHCP, but it would be nice for the Asus to be more robust. I have had "Continuous" mode set for the last few months, which I think has helped, but not solved the problem. From the SSH terminal I can see the WAN interface has the correct public IP address, but something is stopping the ASUS from sending traffic. Very odd.

Thanks for the link to the Wiki, I have touched those files to see if anything appears in the log.
 

BamaInArk

Occasional Visitor
Just some thoughts on this subject. The WAN IP does not come through your cable modem itself but through your ISP DHCP servers through the modem of course. On older routers there used to be a DHCP Release/Renew button/option. Newer routers(Asus ones at least) this apparent option is missing. You might try looking at the router Network Map page. Click on the "World" looking icon near the top where it says Internet status: Connected. This will take you to a different screen to the right where you can toggle the internet connection ON|OFF. I think this will basically cause a release/renew cycle. Not sure if that will work or not. I wonder if this may be an issue with the ISP itself vs the slow recovery being blamed on the router.

I had an older Netgear router that seemed to take forever to recover similar as what you're seeing with the occasional ISP drop. Once I got rid of that router and went to Asus that issue stopped. So it had to be something peculiar with that device.

Still in your case it should renew fairly quickly. But you've got to determine if the problem is on your end or theirs!
 

MrRederick

Occasional Visitor
The WAN IP does not come through your cable modem itself but through your ISP DHCP servers through the modem of course.
Majority of ISPs, including mine, around the world provide the global IP through the modem to the Asus via DHCP. However there are some that the modem is acting as a router and a private IP is used between the IP and the Asus, which confuses matters. I think one of the previous posters might have this.

In my case your suggestion (ON/OFF) is exactly what fixes my problem, restarting the WAN interface in the ASUS which appears to ask the DHCP client to try again. This is surprising as I thought it was what the "continuous" mode was supposed to fix.

I have implemented the ChkWAN script, and it is checking every 5 minutes, filling my syslog with info, so I will hopefully find out this week if it has helped.
 

BamaInArk

Occasional Visitor
Majority of ISPs, including mine, around the world provide the global IP through the modem to the Asus via DHCP. However there are some that the modem is acting as a router and a private IP is used between the IP and the Asus, which confuses matters. I think one of the previous posters might have this.

In my case your suggestion (ON/OFF) is exactly what fixes my problem, restarting the WAN interface in the ASUS which appears to ask the DHCP client to try again. This is surprising as I thought it was what the "continuous" mode was supposed to fix.

I have implemented the ChkWAN script, and it is checking every 5 minutes, filling my syslog with info, so I will hopefully find out this week if it has helped.
I probably didn't word the quoted text correctly. What I meant to say was the WAN IP does not come FROM the modem but through it(which I think I added later) And yes some modems/routers combined, also known as a Gateway Device, operate slightly different. Also Modems get their own IP address from you ISP but those are typically hidden from the user. Any device connected to the internet will have it's own IP address. So in both cases, stand alone modem/stand alone router(2 IPs) or a Gateway Device(2 IPs) the modem hardware will have a hidden IP address typically not visible to the user.
 

MrRederick

Occasional Visitor
The ChkWAN script appears to be working, checking my syslog the router has twice now reconnected itself, both times in the early hours, without my noticing when I next needed it. Fantastic!
 

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