If you cpanel sites has the fixed IP address, you can set policy routing to make the traffic go to specific WAN port. Please see the following FAQ. Make the destination as your cpanel IP, service type as any. https://www.tp-link.com/en/support/faq/2134/

@Andone 

thank you for your reply, my c panel didn’t have a static IP and I’m facing this issue with many sites most of them having SSL certificates, so i know that there was an option in other load balancers to to keep the session in the same WAN without changing it.

is this available in my TP-Link model?

Yes thats it. I tried and it is working fine. many thanks

unfortunately after a while the error occurred again (IP changed, try to login again). it seems not this the option :(

@IMN 

 

I check TP-LINK User Guide.

 

>>>

With Application Optimized Routing enabled, the router will consider the source IP address and destination IP address (or destination port) of the packets as a whole and record the WAN port they pass through. Then the packets with the same source IP address and destination IP address (or destination port) will be forwarded to the recorded WAN port. This feature ensures that multi-connected applications work properly.

 

When you access your cpanel, if destionation IP address or destination port doesn't change, the data will go to the same WAN. If not, they may go different WAN ports. 

 

Other solution:

Maybe you can make sure what IP address or destination port will be used to access your cpanel, then consider to meet your demand thorugh Policay Routing function.

 

thanks for your reply.