Unbuntu with 2 Network cards.

Chan Chung Hang Christopher christopher.chan at bradbury.edu.hk
Sat Jun 5 03:21:20 UTC 2010

Maxime Alarie wrote:
> Good day,
> I have a Ubuntu server 9.1  server with 2 nics.  I would like to  put 
> one Nic outside my firewall (public) and the other inside my firewall. 
> Both nics wont be on the same subnet. Communications will be 
> “impossible” between the 2 interfaces.  root cant ssh on this server as 
> well..
> Would you, as linux experts trust such a setup?  There will be no 
> sensitive information on this server. Just  small  demo applications on 
> a webserve for some clients to try.  I never created that kind of setup  
> so im not  sure how to proceed.

Sure. Standard setup for nat gateways and other stuff like http proxies 
except that nat gateways would enable communications between interfaces. 
I would also use that if the box need to face the public but had its 
user security database hosted internally but I would take pains to 
ensure public facing services are secure.

I already have a setup similar to what you describe save for 
communication being allowed between interfaces (natting and internal 
routing - box connects internet to multiple internal vlans) and another 
setup where the box has two internet interfaces (different broadband 
connections from two isps) and an internal interface.

Since you just have a single Internet connection and only two 
interfaces, there is really nothing special that you need to do besides 
configuring the two interfaces. No routing table/routing rule magic 
necessary. If you had two Internet facing interfaces, then you need to 
know how to use iproute2 toolchains.

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