ESXi Guest e1000 tweaks

Windows

Refer to this KB article @ VMWare
Poor network performance on Windows 2008 Server virtual machine

Linux

    Disable TCP Segmenation Offload
    ethtool -K eth0 tso off
    ethtool -K eth1 tso off
    Increase Descriptors
    ethtool -G eth0 rx 4096 tx 4096
    ethtool -G eth1 rx 4096 tx 4096

    You can either add these to rc.local (or your distros equivalent) or my preference is to create a package (rpm/deb) so you can push/pull these to systems easily.

    You could also create /etc/modprobe.d/e1000.conf and add the below

    alias eth0 e1000
    options e1000 RxDescriptors=4096,4096 TxDescriptors=4096,4096

    and/or in /etc/network/interfaces:

    auto eth0
    iface eth0 inet dhcp
         up ethtool -G eth0 rx 4096 tx 4096
         up ethtool -K eth0 tso off

If you are still experiencing issues, you may just need to bite the bullet and use the vmxnet3 driver which has eliminated packet-loss/drops in the large majority of cases.