[lug] 2 IPs, one DSL

David Anselmi anselmi at anselmi.us
Sun Jun 6 13:08:57 MDT 2004

Elyse M. Grasso wrote:
> Is there a good, reasonably current source online that discusses hardware and 
> software configurations and security considerations for a set-up like this?

If you use Qwest as your ISP see:


for directions on setting up your DSL modem.  If you have a different 
ISP, check with them and your Linksys manual for using multiple IPs with it.

As for security considerations, I guess _Building Internet Firewalls_ 
from O'Reilly would be good.  I see they have _The Best Damn Firewall 
Book Period_, which is newer but I don't know anything about it.

The main security issue you'll face is that currently NAT protects all 
ports you don't specifically allow (via DNAT).  If you put machines on a 
subnet using public IPs you may expose ports you don't want to.  A 
firewall is a typical way to protect those ports.

You don't necessarily need a (stand alone) firewall if you continue to 
do NAT, if you do port filtering on the Linksys, if each server only has 
public ports open, or if you use iptables to filter ports on each server.

Depending on the time you have and the complexity of your applications 
it might be worthwhile to hire a consultant.  Or keep asking here.


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