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2. What is needed
This section describes what is needed for the authentication gateway.
2.1. Netfilter
The authentication gateway uses Netfilter and iptables to manage the firewall. Please see the Netfilter HOWTO.
2.2. PAM for Netfilter rules.
This is a pluggable authentication module (PAM) written by Nathan Zorn that can be found at http://www.itlab.musc.edu/~nathan/pam_iptables.
2.3. DHCP Server
The authentication gateway will act as the dynamic host configuration protocol (DHCP) server for the public network. It only serves those requesting DHCP services on the public network. I used the ISC DHCP Server .
2.4. Authentication mechanism
The gateway can use any means of PAM authentication. The authentication mechanism the Medical University of South Carolina uses is LDAP. Since LDAP was used for authentication, the pam modules on the gateway box were set up to use LDAP. More information can be found at http://www.padl.com/pam_ldap.html. PAM allows you to use many means of authentication. Please see the documentation for the PAM module you would like to use. For more information on other methods, see pam modules.
2.5. DNS Server
The gateway box also serves as a DNS server for the public network. I installed Bind, and set it up as a caching nameserver. The rpm package caching-namserver was also used. This package came with Red Hat.