Ok, sorry, you can ignore my last message. Because of the problems I had with NFS, I assumed that the networking problems of my new machine are als the fault of NFS. But I checked it more detailes and found out, that the Ethernet-Adapter of my new machine was faulty. I replaced it and NFS works now fine on the new machine. Tough on the old machine, the problems still exist.
Ok, sorry, you can ignore my last message. Because of the problems I had with NFS, I assumed that the networking problems of my new machine are als the fault of NFS. But I checked it more detailes and found out, that the Ethernet-Adapter of my new machine was faulty. I replaced it and NFS works now fine on the new machine. Tough on the old machine, the problems still exist.