i have the same problem:(

Might be that the detection uses a DNS server to ping it for the test.

Maybe your provider did not provide a pingable DNS via DHCP? Try to set Google DNS 8.8.8.8 / 8.8.4.4 for the WANs instead?

Firmware Version: 1.1.0 Build 20150526 Rel.71817s
Hardware Version: TL-R470T+ v4.0

These are my online detection settings for my UMTS-Router
Port: WAN4
Detecting: Activate
Mode: Manual
Ping: 8.8.8.8
DNS Lookup: 0.0.0.0

Problem:

If my R470T+ is in the state
"WAN4 Active Online Detection failed."
it doesn't come back, if the UMTS connection is good after some time.

In other words: Offline detection works, Online detection does not.


Notes:
The UMTS-Connection is very unstable, the signal goes and comes.
The DNS-Lookup feature I have to deactivate, because it's a router it always would detect online.
The same if Detecting is inactivated.


My questions to TP-LINK:
Is there a timeout after that a link comes back to online state ?
How is the online detection feature internal working ?
Please make this feature more transparent and more adjustable.

The DNS-Lookup feature I have to deactivate, because it's a router it always would detect online.
The same if Detecting is inactivated.

Why? If everything works, one surefire sign is that the box will be able to resolve something via Google (other other) DNS-Server. Or did I get you wrong?

Maybe the unstable UMTS is the real reason - try somewhere else?

UMTS and such often don't assign "real" IPs to your interface but IP from private (unroutable) networks like 10.x.y.z so you won't be able to DynDNS back to the box.

ande wrote

Why? If everything works, one surefire sign is that the box will be able to resolve something via Google (other other) DNS-Server. Or did I get you wrong?

Maybe the unstable UMTS is the real reason - try somewhere else?

UMTS and such often don't assign "real" IPs to your interface but IP from private (unroutable) networks like 10.x.y.z so you won't be able to DynDNS back to the box.

Since 3 months ago, we have the problem in my region that the german Telekom is not able to provide a stable UMTS signal. I'm living in a small village, DSL would be only about 768kBit/s. So you understand, I can't change the location. Besides that I need an outdoor antenna for UMTS. Indoor the signal is always 0%, outdoor it is always 100%. I can see the mobile phone mast above the roof-edge. An 30m Ethernet-cable connects to the TL-R470T+ router. The UMTS-Router is not an USB-Stick with PPPoE, I' have configured a static route. The idea now is to put a DSL WAN and a UMTS WAN together with a load balance router. This as background to understood better.

Back to my problems.

The DNS-Lookup feature always leads to a "WAN is online" state, it doesn't care if the UMTS connection is down. In other words. Although traceroute doesn't reach its destination, the result is "WAN is online". Is it clear now ? I can't need this feature.

On the other side can I ping successfully 8.8.8.8 with the R470T+ Maintenace -> Dignostics page. Anyhow the R470T+ remains in the state "Online Detection Failed" forever ? I alwas have to put it manual back to Online, if the UMTS signal is good again.

Ok I understand - I think that's a case for the German support:

TP-LINK Deutschland GmbH
E-Mail: [EMAIL="support.de@tp-link.com"]support.de@tp-link.com[/EMAIL]
Robert-Bosch-Straße 9, 65719 Hofheim am Taunus
Tel (14ct/min aus dem Telekom-Festnetz, bis zu 42ct/min aus Mobilfunknetzen): 01805 TPLINK (01805 875465 )

They answered to me.... good luck!

The successful ping to 8.8.8.8 might use a different WAN than the UMTS link..?

ande wrote

Ok I understand - I think that's a case for the German support:

TP-LINK Deutschland GmbH
E-Mail: [EMAIL="support.de@tp-link.com"]support.de@tp-link.com[/EMAIL]
Robert-Bosch-Straße 9, 65719 Hofheim am Taunus
Tel (14ct/min aus dem Telekom-Festnetz, bis zu 42ct/min aus Mobilfunknetzen): 01805 TPLINK (01805 875465 )

They answered to me.... good luck!

The successful ping to 8.8.8.8 might use a different WAN than the UMTS link..?

I wrote an email to TP-Link on 09-19-2015. But I didn't get an answer until today. OK it was weekend.

The successful pinging is as follows:
Go to the router menu at 192.168.0.1 ->Maintenance -> Diagnostics
Then choose WAN4 (the WAN for the UMTS-Router)
Ping 8.8.8.8 gives answer less den 100ms, means connection is good.
Go to the Online Detection screen and see
WAN4 | Active | Online Detection failed.

This looks like a bug to me.

The router needs about 30s to change from online to offline detection and vise versa.

If the Internet connection of a WAN port changes in a shorter time interval the router gets confused and persists in offline status.
This problem is reproducible. Go to your modem router and change the PPP settings from wrong to right and vise versa within 10s.

Reported that bug in detail (Wireshark recording) to TP-Link at 30. September 2015, after I have been demanded to do so and I'm still waiting for an answer.
That was my third mail to TP-Link. To my first two mails I got an answer after one week. No comment to the support from TP-Link and their practice with a gratis hardware tester.

The job does much better now an cheap, old DLINK DIR-300 router, that I bought from ebay for 1€ some weeks ago, with OpenWrt 12.09. and multiwan (plus Wifi and firewall integrated).

Sure that was the hard way to concern myself with OpenWRT, but it's worth it.

Best regards,
Andreas