I have two wan links and using PCC method for load balancing.
One wan UPLINK is 512k and second wan uplink is 4Mb,
Currently I see that UPLOAD traffic is reaching only 512Kbps only.
How can I force it to use 2nd WAN link for upload only.
You don’t if you want PCC load balancing. How would you define “upload”? Just a connection you are sending out a lot of data with? A DNS request requires some upload, browsing the web requires some upload, everything you do on the internet requires at least some upload to initiate and maintain the connection. Once NAT is done the connection is set to go out of that link, it would need to be completely broken and reesablished to send it out of another link.
If you know what IP address you are “uploading” to for a specific service, then you can set mangle rules to send it out the link that you want, but it’s not possible to do it based off of the size of the connection or speed of the connection. The best you can do is weight the routes in such a way that it will hit one more often than the other.