Using Your Router as a Firewall
By using a combination of extended access-list filtering options, a Cisco router can be configured to act as a firewall to a secure network. Let's take a look at the configuration example in Listing 8.1. In this example, the access-list assigned to the Ethernet port connecting the internal LAN segment enables TCP sessions that were established by hosts on the internal LAN to WWW servers. The Internet mail protocol (SMTP) is enabled from any host, but only to a single host, 192.168.10.10, the mail server for the company. All other traffic trying to go out the Ethernet interface is dropped.
Code Listing 8.1. Example Configuration for Firewall Router
interface Ethernet description Internal LAN segment ip address ... |
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