Cisco 7604 Configuration Guide - Page 112

Routed Mode Overview Chapter 5 Configuring the Firewall Mode The following steps describe how data moves through the FWSM (see Figure 5-4): 1. A user on the outside network attempts to reach an inside host (assuming the host has a routable IP address). If the inside network uses private addresses, no outside user can reach the inside network without NAT. The outside user might attempt to reach an inside user by using an existing NAT session. 2. The FWSM receives the packet and because it is a new session, the FWSM verifies if the packet is allowed according to the security policy (access lists, filters, AAA). 3. The packet is denied, and the FWSM drops the packet and logs the connection attempt. If the outside user is attempting to attack the inside network, the FWSM employs many technologies to determine if a packet is valid for an already established session. A DMZ User Attempts to Access an Inside Host Figure 5-5 shows a user in the DMZ attempting to access the inside network. Figure 5-5 DMZ to Inside Outside 10.1.2.1 209.165.201.2 FWSM 10.1.1.1 Inside DMZ 92886 User 10.1.2.27 Web Server 10.1.1.3 The following steps describe how data moves through the FWSM (see Figure 5-5): 1. A user on the DMZ network attempts to reach an inside host. Because the DMZ does not have to route the traffic on the Internet, the private addressing scheme does not prevent routing. 2. The FWSM receives the packet and because it is a new session, the FWSM verifies if the packet is allowed according to the security policy (access lists, filters, AAA). 3. The packet is denied, and the FWSM drops the packet and logs the connection attempt. Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall Services Module Configuration Guide using ASDM 5-6 OL-20748-01