Mysterious loss of connectivity

[marcox]

I have same problem and it is the ISP we use and the problem the router not get the new WAN IP. I set a cronjob start every 12h to reconnect WAN. This needs 3-4 seconds and since this i have no connection problems

Perhaps the next firmware have a solution.....

#!/bin/sh
service "restart_wan_if 0"

 

[sbsnb]

I may have missed it, but were we able to determine if you can reach the modem after losing connectivity but before restarting WAN?

 

[Lynx]

Not yet - I can't easily reproduce the issue unfortunately. Do you have any clue what the issue might be? My best guess is that the ISP forces every 48 hours a connection refresh, and this requires obtaining a new WAN IP. My modem sets eth0 down and eth0 back up as it gets new connection, but the ASUS router goes on trying to use the expired WAN IP and this fails. Would that make any sense? I would really like to know what causes this issue.

 

[marcox]

Not yet - I can't easily reproduce the issue unfortunately. Do you have any clue what the issue might be? My best guess is that the ISP forces every 48 hours a connection refresh, and this requires obtaining a new WAN IP. My modem sets eth0 down and eth0 back up as it gets new connection, but the ASUS router goes on trying to use the expired WAN IP and this fails. Would that make any sense? I would really like to know what causes this issue.

Right, same i have! But only with my Asus router - not with other 4G Routers!

 

[Lynx]

marcox do you also use a 4G LTE modem? Does it refresh (disconnect and reconnect to ISP) every 48 hours like mine? Can you check logs of your modem?

 

[sbsnb]

Not yet - I can't easily reproduce the issue unfortunately. Do you have any clue what the issue might be? My best guess is that the ISP forces every 48 hours a connection refresh, and this requires obtaining a new WAN IP. My modem sets eth0 down and eth0 back up as it gets new connection, but the ASUS router goes on trying to use the expired WAN IP and this fails. Would that make any sense? I would really like to know what causes this issue.

I can't figure out whether the issue is your modem's WAN IP or your router's WAN IP. It could just be that the modem is borked and by the time you notice and restart the WAN enough time has elapsed that the modem has fixed its own issue. If you are able to ping or log in to the modem when this happens the issue isn't your router.

 

[Lynx]

My modem is set to bridge mode. Does this mean it gets assigned a WAN IP? If so what assigns its IP? I believe my ASUS router takes on WAN IP from ISP right? Does my modem take on an IP from the ISP too? I thought in bridged mode it shouldn't have a WAN IP?

My gut feeling is that the issue is not with my bridged modem. It's a pretty sophisticated 4G LTE device.

 

[marcox]

marcox do you also use a 4G LTE modem? Does it refresh (disconnect and reconnect to ISP) every 48 hours like mine? Can you check logs of your modem?

I have the Asus 4G-AC86U here in use with only the inside LTE modem as internet connetction. No DUAL WAN or someting else. My Router have same strange problem. It was disconnect after 12 hours, lost internet.... no reconnect till i restart WAN. When i insert the card in a Huawai Router it works without problems

 

[Lynx]

When you lose connection again can you please post sylog output here? And before you do can you SSH into your router and then issue these commands:

touch /jffs/scripts/dhcpc-event
chmod 755 /jffs/scripts/dhcpc-event

This just makes sure that extra log entries relating to WAN IP capture get added to the syslog output.

 

[dave14305]

When you lose connection again can you please post sylog output here? And before you do can you SSH into your router and then issue these commands:

touch /jffs/scripts/dhcpc-event
chmod 755 /jffs/scripts/dhcpc-event

This just makes sure that extra log entries relating to WAN IP capture get added to the syslog output.

That won’t work on his stock firmware.

 

[marcox]

When you lose connection again can you please post sylog output here? And before you do can you SSH into your router and then issue these commands:

touch /jffs/scripts/dhcpc-event
chmod 755 /jffs/scripts/dhcpc-event

This just makes sure that extra log entries relating to WAN IP capture get added to the syslog output.

I have same log like u had and post here..... so i solve the problem with the cronjob and restart my wan every 12 hours.... so i have NO connection problems anymore. To get new logs i must remove the cronjobs first and wait... but i think WE solve this problem not, especially when we us the stock firmware.

 

[Lynx]

I have same log like u had and post here..... so i solve the problem with the cronjob and restart my wan every 12 hours.... so i have NO connection problems anymore. To get new logs i must remove the cronjobs first and wait... but i think WE solve this problem not, especially when we us the stock firmware.

Likewise I have set up 'network monitoring' in the modem GUI (ping and DNS), and checking through the ASUS wanduck.c source code (slightly terrifying in size), and playing around with settings and monitoring using tcpdump (see few posts above), I gather that that should detect internet down and then restart WAN.
But like just rebooting the router, using this 'network monitoring' facility doesn't actually get to the root of the problem. I am keen to figure out what the real problem is.

 

[sbsnb]

My modem is set to bridge mode. Does this mean it gets assigned a WAN IP? If so what assigns its IP? I believe my ASUS router takes on WAN IP from ISP right? Does my modem take on an IP from the ISP too? I thought in bridged mode it shouldn't have a WAN IP?

My gut feeling is that the issue is not with my bridged modem. It's a pretty sophisticated 4G LTE device.

I'm wondering if it's really in bridge mode, or half-bridge.

 

[marcox]

Likewise I have set up 'network monitoring' in the modem GUI (ping and DNS), and checking through the ASUS wanduck.c source code (slightly terrifying in size), and playing around with settings and monitoring using tcpdump (see few posts above), I gather that that should detect internet down and then restart WAN.
But like just rebooting the router, using this 'network monitoring' facility doesn't actually get to the root of the problem. I am keen to figure out what the real problem is.

Should we do the Asus work? It is a bug in Firmware. But u r right - it is interesting to find out what is the problem. I try many days with different settings and i found more and more bugs in this Firmware. So i decide to restart my WAN not reboot the router. Re-start WAN automatically needs 3-4 seconds and all is o.k.! I wait for the next firmware ... i waste time enough on this problem. But for YOU -> GOOD LUCK!!!

 

[Lynx]

I'm wondering if it's really in bridge mode.

I think it is because the ASUS router seems to get assigned a WAN IP form my ISP and traceroute shows next hop my ISP:

tracert www.google.com

Tracing route to www.google.com [216.239.38.120]
over a maximum of 30 hops:

  1    <1 ms    <1 ms    <1 ms  RT-AX86U-4168 [192.168.1.1]
  2    50 ms    46 ms    47 ms  10.8.1.1

2nd hop is clearly over LTE (circa 50ms).

 

[sbsnb]

We're not interested in whether your modem is a hop in the route, we're interested in whether your router can reach the modem when the issue is happening.

 

[Lynx]

OK but the LTE device is in bridge mode, yes?

 

[sbsnb]

Yes, but that doesn't mean it plays no role. All bridge mode is essentially is a router configured with DMZ set to your Asus' IP. It still there shuttling packets back and forth. If you can't reach the modem, the problem is with the Asus. If you can reach the modem the problem is with the modem.

 

[Lynx]

Yes, but that doesn't mean it plays no role. All bridge mode is essentially is a router configured with DMZ set to your Asus' IP. It still there shuttling packets back and forth. If you can't reach the modem, the problem is with the Asus. If you can reach the modem the problem is with the modem.

Understood. From memory when the issue happened before I could not reach the modem. It's frustrating that the problem manifests every 48 hours. One time I could recreate the issue by simply rebooting my modem, but I don't understand why rebooting forced the issue then. After reboot of modem again ASUS was borked until I rebooted ASUS.

 

[sbsnb]

I suspect it's a timing issue between the modem and the Asus. Not knowing the particulars of your modem makes it difficult to do anything but guess. Yours may be an LTE passthrough modem, but usually that means you cannot reach the modem in any way through the router, even when everything's working correctly. In that case, to connect to the modem's management interface would require a connection separate from the router.