@pajtaz 

Interesting.  Probably the easiest way would be to setup a weekly or monthly reboot schedule for your router (3AM on a Sunday?).  There are other very valid reasons for doing this with an ER605 anyways :)

Hello @pajtaz,

pajtaz wrote

It seems that ISP does something to the IPv6 address every month because about once a month any services or applications on local network that use ER605 as the DHCP server and router stop working until I renew IPv6 address of the ER605. I have to manually go into ER605 and "Renew" IPv6 address then all the services and applications that did not work before the renewal end up working correctly.

The router ER605 should update the IPv6 address automatically once your ISP assign a new IP address.

Could you capture the WAN port packets of ER605 when this issue occurs next time?

Here is the detailed steps of the packets capture you may refer to:

1. Reproduce the issue.
2. Please connect a PC with Wireshark to ER605, set the Port Mirroring on the ER605(mirror the port connected to PC to ER605 WAN port).

You can configure it both in Standalone Mode and Controller mode, and please refer to the following steps to configure it in Controller Mode.

Click on the ER605 in Device List, go to Ports in the Details window, and refer to this screenshot:

3. Start capturing, click on Disconnect to release the IP address, and click on Connect to renew the IP.
4. Stop capturing and save the packets file.

Hello @pajtaz,

Thank you so much for taking the time to post the issue on TP-Link community again!

To better assist you, I've created a support ticket via your registered email address, and escalated it to our support engineer to look into the issue. The ticket ID is TKID230827843, please check your email box and ensure the support email is well received. Thanks!

Once the issue is addressed or resolved, welcome to update this topic thread with your solution to help others who may encounter the same issue as you did.

Many thanks for your great cooperation and patience!