Bug in TL-R470T+ for SIP Connections and DynDNS

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Bug in TL-R470T+ for SIP Connections and DynDNS

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Bug in TL-R470T+ for SIP Connections and DynDNS
Bug in TL-R470T+ for SIP Connections and DynDNS
2018-06-21 05:07:22 - last edited 2021-04-20 11:38:49
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I would like to report 2 bugs which I believe I could find on product Loadbalancer TL-R470T+.

Bug 1:

I have a TL-R470T+ v4.0 running firmware 20150526 Rel.71817s (latest version available) which I use purely for Active/Backup Internet with two different connections. Behind this TL-R470T+ I have some equipment like SIP Clients (an ATA hardware) and which connect to an external VoIP server in the Internet. When a Internet failover occurs from WAN1 to WAN2 the only thing that doesn't keep working are the SIP Clients.

Looking at Maintenance, "NAT Table" I can see the the previously opened connection to the SIP server keeps bounded to go out via WAN1 although the connection is already down and everything is going out via WAN2. Even if I restart the SIP Clients it doesn't work and it is unable to connect. Looking again at NAT Table it can still see that same connection trying to go out via WAN1 which is Down.
If I reboot the TL-R470T+ (and it clears the NAT Table) then it works again and the SIP Clients can connect.

The solution to that perhaps could be clear the NAT Table when a failover occurs from one WAN port to another.

Bug 2:

One of the TL-R470T+ I have the WAN2 is primary and WAN1 is secondary. However when I have both connections Up and everything is going out via the primary (WAN2) the Services, Dynamic DNS, DynDNS doesn't change the "WAN Port" to WAN2, but keeps choosing WAN1 which is secondary and is in standby. I have even rebooted the TL-R470T+ but with no effect, it keeps sending to DynDNS service the WAN1 IP address which is wrong.

Solution is make the DynDNS aware of which is the primary connection or make the service to know which is the correct Public IP and send the correct one to the DynDNS service.
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#1
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Re:Bug in TL-R470T+ for SIP Connections and DynDNS
2018-06-25 17:44:56 - last edited 2021-04-20 11:38:49
what's the configuration of your link backup, post the screenshots, please. DDNS module has nothing to do with link backup feature in design.
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Re:Bug in TL-R470T+ for SIP Connections and DynDNS
2018-06-26 09:48:32 - last edited 2021-04-20 11:38:49
Configuration for the backup link is very similar to the primary one, Static IPs.

The issue is in another area. The Loadbalancer feature when it fails over one link to another it doesn't clear the NAT table. As a result the opened SIP connections keep trying to go out via the already offline link/interface.
If the NAT Table could be cleared upon each failover it would probably resolve the issue as rebooting the Loadbalancer and keeping only the backup link connect then it works after the reboot.

DDNS module must have either the ability to choose the WAN connection which is currently primary or send out the Public IP of the active connection in order to update the service.
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Re:Bug in TL-R470T+ for SIP Connections and DynDNS
2018-06-26 17:55:42 - last edited 2021-04-20 11:38:49
DO you know NAT table have aging time? From principles, I don't think NAT table and DDNS should correspond to Link Backup feature.
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Re:Bug in TL-R470T+ for SIP Connections and DynDNS
2018-06-27 02:08:53 - last edited 2021-04-20 11:38:49
Well, no problem for NAT Table to having ageing time. What doesn't seem to make much sense is a connection be kept opened and trying to go out via a link which doesn't exist any more. That's why I suggested whenever a failover from Active to Backup link occurs to be able to automatically clean the NAT table, otherwise the only solution is reboot the Loadbalance otherwise it can impact the applications behind it for a reasonable amount of time which goes against the propose to have a Loadbalance equipment to be used for failover proposes and reduce impact on a internet link down.

If DDNS should not correspond to Link Backup feature, not even be able to choose the interface I want to advertise its Public IP address and DDNS module is fixed in WAN1 what is it serve for if: 1) WAN1 is offline or 2) If I do not wish to use the WAN1 as primary ? DDNS module should be able, by whatever way, to advertise the necessary Public IP address so the incoming connections can work properly.
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