Increase network throughput

On some operating systems, the default network settings limit the possible TCP throughput. If you find that your Linux VM is not able to push more than 20 MB/s on a gigabit port, then open /etc/sysctl.conf in an editor and add at the bottom:

net.core.rmem_max=16777216
net.core.wmem_max=16777216
net.ipv4.tcp_rmem=4096 87380 16777216
net.ipv4.tcp_wmem=4096 65536 16777216

Once saved, execute sysctl -p and try a test download.