Which "side" do you want to limit to NFSv4? That is, you've got EndClient <=> Ganesha PROXY_V4 <=> Backend (NFSv4) PROXY_V4 only speaks NFSv4 (it's basically a strange V4 client), so between Ganesha and your backend, you'll only see NFSv4 traffic. Are you asking how to make Ganesha only respond to v4 *Clients*? If so, set Protocols = 4 in your ganesha config (this can be either per export, or global via NFS_CORE_PARAM)