Re: [Hampshire] Network numpty

On Monday 20 Nov 2006 06:44, Tony Whitmore wrote:
> Jamie Webb wrote:
> > On Sun, Nov 19, 2006 at 11:43:22PM +0000, Cayenne-uk wrote:
> >> I am involved in a debate regarding the number of nics needed on a Linux
> >> server.
> >>
> >> The Scenario: Two or more PCs need to be connected on a LAN. A PC will
> >> be set up as a server, providing email, firewall, files etc. So all
> >> internet traffic from the other PCs should of course go through the
> >> server, connected up through a hub. A fairly standard set up. Obviously
> >> the server would have to address the IPs of the internal LAN, as well as
> >> deal with the external ISP connection.
> >>
> >> The question is - how is all this normally wired up? More specifically,
> >> must the server have two network ports (ie nics)? (One for the LAN via
> >> the hub, and one to connect to the ADSL), or can the ADSL connection AND
> >> the LAN be handled through one network port?
> >
> > In principal you can use a single NIC and it will work, but it's a
> > very bad idea, mainly for security reasons. The standard and strongly
> > recommended approach is to use two.
>
> In principal it's a bad idea to combine the service roles (e-mail, file
> serving) with security (firewall). It's a much better plan to use
> different boxes. For a small network, the firewall box can be an *very*
> old PC.
>
> If you have an ADSL card (PCI) or a USB ADSL modem, then that negates
> the need for a second NIC.

So the second IP can be entered in a ppp file and that provides the second
interface? And one needs two cables (one going to the internet/adsl and one
going to the private network?

Presumably, if instead of a modem, one has a single port "router", with an
RJ45 connection (which most people advocate with Linux rather than an adsl
modem), then one needs two interfaces - i.e. 2 cards - and two separate cat5
cables going to the 2 separate NICs/interfaces?

The "aboutdebian website says

<quote>Adding A Second Network Card

Setting up a proxy or firewall system requires that the system have two NICs
so you would have to add a second network card to your existing networked
Debian system. If you want to use a Linux system as a router you would have a
system with multiple NICs, one for each of the subnets you wish to
interconnect. </quote>

Is this in fact wrong?

(Sorry - I was one of those involved in the debate and I was saying that I
could not understand how one network card could handle 2 IPs and 2
interfaces. I'm afraid I still don't. :-( Perhaps someone could show me at
the next BaB.)

Lisi