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8-2
Cisco Secure Router 520 Series Software Configuration Guide
OL-14210-01
Chapter 8 Configuring a Simple Firewall
Figure 8-1 shows a network deployment using PPPoE or PPPoA with NAT and a firewall.
Figure 8-1 Router with Firewall Configured
In the configuration example that follows, the firewall is applied to the outside WAN interface (FE4) and
protects the Fast Ethernet LAN on FE0 by filtering and inspecting all traffic entering the router on the
Fast Ethernet WAN interface FE4. Note that in this example, the network traffic originating from the
corporate network, network address 10.1.1.0, is considered safe traffic and is not filtered.
Configuration Tasks
Perform the following tasks to configure this network scenario:
• Configure Access Lists
• Configure Inspection Rules
• Apply Access Lists and Inspection Rules to Interfaces
A configuration example that shows the results of these configuration tasks is provided in the
“Configuration Example” section on page 8-5.
1 Multiple networked devices—Desktops, laptop PCs, switches
2 Fast Ethernet LAN interface (the inside interface for NAT)
3 PPPoE or PPPoA client and firewall implementation—Cisco Secure Router 520 Series router
4 Point at which NAT occurs
5 Protected network
6 Unprotected network
7 Fast Ethernet or ATM WAN interface (the outside interface for NAT)
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