Cisco 678 modem/router and Linux server Q

xmutex · 08-11-2001, 01:27 AM

So I used to have cablemodem, and happily ran my own domain server, doing my e-mail/web stuff.

I moved across the country and now have DSL. I was supplied with a Cisco 678 modem/router.

My dilemma: in the cablemodem days, eth0 had the external IP and eth1 was the IP masquerading for my two other boxen.

Now it seems my Cisco does all the PPP dialup, thusly it receives the external IP and then I can get a LAN with a hub.

I don't think I want this. I want all traffic to my IP to go through my Linux box. I can't get but one IP through Qwest, so I'm not sure if this situation is salvageable.

Any info/flames appreciated

_Ec|ipsE_ · 09-03-2001, 04:27 AM

Well, you have a few options when it comes to solving your problem...

The option I would suggest is switching ISP providers to one that uses bridging mode instead of PPP mode. Bridging mode makes the router invisible from an IP standpoint, and your home network will be directly connected to the net.

The setup I use normally is a 675 with bridging mode connected directly to the net, then in my server I have 1 NIC with 2 IP addresses assigned to it. The first address uses DHCP and fetches the external IP from my ISP. The second address is a local IP (192.168.0.1 for example).

Then, all you have to do is assign local addresses to your other systems... setup IP Masq as you would normally do, and you're off!

Your other systems will not be able to communicate with the internet directly, even though they are all on the same hub, and you only have 1 NIC in your server.

If you wish to stay with your current provider...

By default, the 678 will use a 10.0.0.x setup for it's local IPs, with the router being assigned 10.0.0.1 - all you have to do is use 10.0.0.2 (or DHCP) for the first interface on your server, and then on your second, use a different class of local IPs (i.e. 192.168.0.x). This way there is no way that they will be able to communicate directly with the router. Then, on your server, make 10.0.0.1 your gateway, and on the other systems, make your server's 192.168.0.x IP the gateway... your all set.