The stock vmware image of Astaro uses the flexible virtual NIC type configured as AMD PCNET.
According to VMWare, that is the slowest option, e1000, vmxnet and vmxnet3 are, in order, faster.
My setup is as follows: Astaro routes on vmware, I have one virtualized linux using an e1000 NIC in a DMZ, and one virtualized linux using an e1000 NIC in the main network segment, a DSL modem connects to the internet.
If I use vmxnet3 on the DSL interface, it can't connect to the DSL AC anymore, it says, and the internet connection stays down.
If I use vmxnet, that works, but if I use either of the vmxnet types, copying stuff from the one to the other linux server inside vmware by way of the Astaro firewall is very slow, on the order of 1K/sec.
As a result, I'm reduced to e1000, which is quite fast, but it would be nice if the vmxnet stuff worked.
FYI, that problem has been there as long as I've been using vmware (since v8, I think).