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Cisco ASA 5500 Series Configuration Guide using ASDM
OL-20339-01
Chapter 5 Configuring the Transparent or Routed Firewall
Firewall Mode Examples
An Inside User Visits a Web Server
Figure 5-8 shows an inside user accessing an outside web server.
Figure 5-8 Inside to Outside
The following steps describe how data moves through the adaptive security appliance (see Figure 5-8):
1. The user on the inside network requests a web page from www.example.com.
2. The adaptive 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 adaptive security appliance first classifies the packet according to a
unique interface.
3. The adaptive security appliance records that a session is established.
4. If the destination MAC address is in its table, the adaptive 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 adaptive security appliance table, the adaptive 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 adaptive 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
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