I'm sharing some other stuff with smb on the same server and I've never had any problem with that so I don't think there's anything wrong with the NIC or the cables.
I checked mtu and it's 1500 on both. Thanks for the suggestions though!
I have a server running Esxi 5.5 and I want to store my virtual machines on my file server running Windows Server 2012 R2.
When I try to install Debian it says something like "Failed to write to sda1", if I hit "try again" it works perfectly.
The same happens when I try to install Windows...