How does ip masquerading work (overview)?

[kgleason at ma.ultranet.com (Kevin M. Gleason)]

Mark,

Actually the outside is connected to me via several T1's, and I'm using my
Linux box as a router between local network (10BaseT) and 100BaseT (so as Ally
McBeal would say, size makes a difference). I need the 100M nic to face the
wall outlet (T1 etc.) and the 10M nic to face the 10M Hub.
I do plan an upgrade to 100M throughout but wanted to get all of the
software/hardware working with 'what I got' before I go asking for 'what I
don't got'.
I haven't looked at the internals of masq but when I try to ping the router
eth0 the 100M nic card kicks in (which has a different IP address than the
network) so the connection fails.
Thanks

"Mark J. Dulcey" wrote:

> "Kevin M. Gleason" wrote:
> >
> > I assume that eth0 is the default for the internal network, is the other
> > (eth1 or whatever) assumed to be the outside world?
> > I have my 10baseT card set up for eth1 and 100baseT set for eth0. If
> > line one is correct how can I change it so the internal network (running
> > 10 M) will see the 10 M side of my Linux box (and the outside world will
> > see me as a 100 M connection?
>
> There's really no particular magic that says that eth0 is the internal
> network and eth1 is the external network. It all comes down to how you
> configure your cards and routing. If you're talking about using a
> distribution that automatically sets up masquerading, it's easiest to
> stick with whatever the distro wants.
>
> It's not likely that there is any advantage to using the 100Mbps card to
> connect to the outside world. Of course, if you have an Internet
> connection faster than 10Mbps, there is. And I'm jealous. You might well
> upgrade your LAN to 100Mbps; it's far more likely than upgrading your
> Internet connection to that high a speed. So I'd stay with the way you
> have things now.
>
> The outside world won't see you as "a 100M connection"; they will see
> you as having whatever size pipe you get from your internet provider. If
> it's cable or DSL, the modem probably doesn't even have a 100Mbps
> Ethernet port.

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