| Figure B |
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| Set up the services you want your firewall to allow. |
The Advanced setup starts out the same, allowing you to choose your network device and select how you want to handle ICMP and service requests. However, unlike with the Simple setup, you can choose whether to use Type of Service (ToS). This allows you to configure iptables to prioritize certain types of traffic by modifying a packet's header. With Firestarter, you can select from three types of traffic: Client Applications, Server Applications, and the X Windows System. Once you have chosen the traffic you want to modify, you select the method for prioritization: throughput, reliability, or delay. Most administrators will not need to touch these options, but if you're running into issues with service availability, you may find ToS helpful. The next step in the Advanced option is to configure masquerading, which is basically a form of network address translation (NAT). This is how you get your machine to act as a gateway for other computers. Masquerading allows the server to route traffic from local, nonroutable IP addresses to outside the network and back again. You'll need to choose the internal interface, often eth1, and your internal network range, as shown in Figure C. By default, Firestarter will autodetect your internal network.
| Figure C |
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| Set up masquerading (NAT) on your firewall. |
| Figure D |
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| Use the Firewall Hits window to watch for hackers. |
With support for ipchains and iptables, Firestarter offers an excellent way to get a firewall up and running with minimal effort on both Linux 2.2 and 2.4 kernels. Its clean interface and excellent wizard make Firestarter suitable for both beginning and experienced administrators. Whether you're creating rules for a stand-alone box or for a complex gateway, you don't have to wade through the manual rule sets any longer. Sit back, relax, and let Firestarter do the heavy lifting.
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