Tweaking NAT configurations
Posted: 13. Nov 2015, 17:20
I am hoping that someone here with actual experience about it, can provide some information. The Virtualbox User-guide section about networking contains a link here, "https://www.virtualbox.org/manual/ch09.html#changenat", in which topics about fine-tuning NAT connections are discussed. I have three questions in relation to these subsections:
9.11.3. Tuning TCP/IP buffers for NAT
As I understand it, this command is given as an example for improving the throughput, "VBoxManage modifyvm "VM guest name" --natsettings1 16000,128,128,0,0". Generally speaking, how can I measure whether these particular settings are improving the throughput? Also, assuming that the effect of this command persists between boots, how would I go about "undoing" these and returning it to their default values?
9.11.4. Binding NAT sockets to a specific interface
Once again, assuming that the effect of this command persists between boots, how would I go about "undoing" it and returning it to its default value, that is,"... [to] route TCP/IP packets through the default interface assigned by the host's TCP/IP stack"?
Finally, I do not understand the difference in the DNS-related effects described in sections "9.11.5" and "9.11.6" even though I read them more than once. In the first of these two sections (9.11.5), it says that I can use the given command to "tell the NAT engine to act as DNS proxy" so as "to hide the DNS server IPs from the guest." In doing so, however, it implies that the guest will still effectively make use of the same DNS servers as those that are configured on the host.
On the other hand, in the second section (9.11.6), the "resolver mode," it states that "the resolver mode will interpret the DNS requests and use the host's DNS API to query the information and return it to the guest." Is the difference between these two procedures the fact that in the first case the request is passed (proxied) to the host to make the resolution, which is then returned to the guest; but in the second case the resolution is made by the NAT engine, not by the host, but still using the host's values for the DNS server? Thanks.
9.11.3. Tuning TCP/IP buffers for NAT
As I understand it, this command is given as an example for improving the throughput, "VBoxManage modifyvm "VM guest name" --natsettings1 16000,128,128,0,0". Generally speaking, how can I measure whether these particular settings are improving the throughput? Also, assuming that the effect of this command persists between boots, how would I go about "undoing" these and returning it to their default values?
9.11.4. Binding NAT sockets to a specific interface
Once again, assuming that the effect of this command persists between boots, how would I go about "undoing" it and returning it to its default value, that is,"... [to] route TCP/IP packets through the default interface assigned by the host's TCP/IP stack"?
Finally, I do not understand the difference in the DNS-related effects described in sections "9.11.5" and "9.11.6" even though I read them more than once. In the first of these two sections (9.11.5), it says that I can use the given command to "tell the NAT engine to act as DNS proxy" so as "to hide the DNS server IPs from the guest." In doing so, however, it implies that the guest will still effectively make use of the same DNS servers as those that are configured on the host.
On the other hand, in the second section (9.11.6), the "resolver mode," it states that "the resolver mode will interpret the DNS requests and use the host's DNS API to query the information and return it to the guest." Is the difference between these two procedures the fact that in the first case the request is passed (proxied) to the host to make the resolution, which is then returned to the guest; but in the second case the resolution is made by the NAT engine, not by the host, but still using the host's values for the DNS server? Thanks.