Hi, proxies are for processing your VMs, and should be focused on sitting near your source VM location.

If you meant gateway server (used to communicate to the dedupe appliance), then you do have the option to specify a gateway server. See: https://helpcenter.veeam.com/docs/backup/vsphere/repository_server.html?ver=110#emc

I am talking about proxy affinity

https://helpcenter.veeam.com/docs/backup/vsphere/proxy_affinity.html?ver=110

Specify it in your backup job on a per-job basis

https://helpcenter.veeam.com/docs/backup/vsphere/backup_job_storage_vm.html?ver=110

In this link they say it can be applied to backup repo, SOBR and cloud repository. Is this dedupe appliance also included in this?

A dedupe appliance is still a backup repo, so I don’t see why you couldn’t, but I can’t say I’ve tried. Hopefully someone else has already tried and has an answer.

If you have defined a backup repository on that dedupe appliance you should be ale to set the proxy affinity for this repo. I am not aware that you can set this specially for the appliance. Veeam is hardware agnostic...

This is exactly correct what Joe said as it is repo not hardware based.