Install dhcp on your gateway, and let your clients be assigned automatic.
If your looking for a good iptables generator, take a look at http://firehol.sf.net .
An external IP could be pinged, so I guess there has to be a misconfiguration of DNS settings?
]]>Do you have your laptop properly configured? Proper gateway set etc.?
Maybe you're running dhcp on your server and/or you allow only specific MACs (or IPs) to connect to the Internet.
Your description is somewhat enigmatic, please brief us with more details :-)
]]>how is that possible? Do I have to change something in some configfiles?
*edit: I also get the following messages in kernel.log when I restart my adsl-connection: Nectar: eth0: no IPv6 routers present
(same for eth1)