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Cisco Security Appliance Command Line Configuration Guide
OL-12172-01
Chapter 15 Firewall Mode Overview
Transparent Mode Overview
An Inside User Visits a Web Server
Figure 15-8 shows an inside user accessing an outside web server.
Figure 15-8 Inside to Outside
The following steps describe how data moves through the security appliance (see Figure 15-8):
1. The user on the inside network requests a web page from www.example.com.
2. The security appliance receives the packet and adds the source MAC address to the MAC address
table, if required. Because it is a new session, it verifies that the packet is allowed according to the
terms of the security policy (access lists, filters, AAA).
For multiple context mode, the security appliance first classifies the packet according to a unique
interface.
3. The security appliance records that a session is established.
4. If the destination MAC address is in its table, the security appliance forwards the packet out of the
outside interface. The destination MAC address is that of the upstream router, 209.186.201.2.
If the destination MAC address is not in the security appliance table, the security appliance attempts
to discover the MAC address by sending an ARP request and a ping. The first packet is dropped.
5. The web server responds to the request; because the session is already established, the packet
bypasses the many lookups associated with a new connection.
6. The security appliance forwards the packet to the inside user.
Management IP
209.165.201.6
www.example.com
209.165.201.2
Host
209.165.201.3
Internet
92408