[plug] network newbie

[Craig Ringer]

> I'm having my first crack at networking two computer: my PC and my bro's 
> laptop. I want to setup the PC as a proxy server for the internet so 
> that the laptop can share the modem (including initialising) connection. 
> I'm reading the LDP PPP-HOWTO which seems helpful to a point but has 
> left me a little stumped.

OK, probably the easiest way is if you're willing to just ssh over to 
your desktop and init the connection from there using whatever dialer 
you use - wvdial, the pon/poff scripts, or whatever. In that case there 
is very little you need to do beyond configuring the ethernet interfaces 
on each machine:
	"ifconfig eth0 <ipaddr> up" for testing,
	 /etc/sysconfig/network for RH-based or /etc/network/interfaces for 
debian for permanant config

... enabling IP forwarding on your "server" machine:
	cat /proc/sys/net/ipv4/ip_forward (to check - 0 is off 1 is on)
	echo 1 > /proc/sys/net/ipv4/ip_forward (temp turn on)

To permanantly turn on ip forwarding you need to edit something (help,RH 
users) in /etc/sysconfig/network and on debian its /etc/network/options

... enabling ip masquerade:
	apt-get install ipmasq (debian)
	[I don't have the foggiest how to go about this on RH-based distros]

... and dial out.

I would strongly reccomend setting up a firewall on your dial-out box, 
see the list archives.

> First of all I don't even know if the Xircom pcmcia ethernet card I 
> bought this morning works. Is there a simple way of testing the to see 
> whether a connection is working?
ping is your friend.
also "ifconfig eth0" will give you some stats etc.
Check the link light on the card if it has one. Are you using a 
crossover cable? do you need to? Have you chosen appropriate IP addr ranges?

> Secondly, the PPP-HOWTO tells me that I need a static IP on the server 
> (the PC) which I can't just make up. So where do I get such an IP?
You shouldn't need a static IP for most purposes - what does it say you 
need one for?

> I 
> thought intranet IPs (192.168.x.x for a class C intranetwork)  were 
> different from external internet IPs. Do I need to use IP Masquerading?
If you intend to use the "private" 192.168.x.x or 10.x.x.x address 
spaces you
_do_ need to use IP masq, yes. I think recent RH has a GUI tool for all 
this, alt see
my comments above.

> I'm now reading the Network-HOWTO, but its age shows a little. Can 
> anyone point me in the direction of a good online HOWTO for networking 
> two computers over an ethernet for a newbie?

IP-Masquerade-HOWTO

-- 
Craig Ringer
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