[vbox-dev] Static route or default gateway for NAT

Maxime Dor max at kamax.io
Mon Oct 3 12:58:26 UTC 2016

Hi Malcom,

That is on purpose - being behind a NAT network means you want to hide 
any subnet connect to that network from the outside world.
Any outgoing connection will look like it came from the NAT Router 
"public" IP.
If you want to allow specific connections to be allowed in, you need to 
configure port forward - so far, I don't think I tell you anything new.

But if you need the "outside" world to know about "inside" networks, 
then NAT is not the right choice. You need to switch to a non-NAT 
solution like Bridged mode (or Host-Only with routing enabled on the 
host) and the "outside" world needs to know about those "inside" network 
with two possibilities:
- Static routes on all routers that need to deal with those subnets
- Internal routing protocol like RIP, EIGRP or OSPF that will 
auto-detect routes and populate routing tables of routers.

On 03/10/16 13:30, Malcolm Clarke wrote:
> Dear Development Group
> I am trying to demonstrate routing in a virtualised network created 
> using VirtualBox with a FreeBSD server acting as router between 2 
> virtual networks. One network is set as NAT Network to allow access to 
> outside world. However, although packets can be directed from the 
> router to the NAT router for outward delivery, the NAT router does not 
> know how to deliver the incoming packets for the "hidden" subnet.
> I wonder if anyone has modified the NAT network to allow simple static 
> routes or default gateway to support this cnfiguration.
> I do not know the interest for this functionality and whether the work 
> is justified for the use that would be made.
> Regards
> Malcolm
> -- 
> *Malcolm Clarke *BSc (Hons), PhD
> Reader in Telemedicine and Data Communication Systems
> T+44 (0) 1895 265053
> *Brunel University London*
> College of Engineering, Design and Physical Sciences
> Department of Computer Science
> HNZW011, Heinz Wolff Building, Kingston Lane, Uxbridge, Middlesex, UB8 3PH
> *www.brunel.ac.uk <http://www.brunel.ac.uk/>*
> Connect with the university on*Linkedin, Twitter, Facebook*
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