Cisco ASA Series Cli Configuration Manual page 159

Chapter 1 Configuring the Transparent or Routed Firewall
An Outside User Visits a Web Server on the Inside Network
Figure 1-11
Figure 1-11
The following steps describe how data moves through the ASA (see
1.
2.
3.
4.
5.
6.
shows an outside user accessing the inside web server.
Outside to Inside
Host
Internet
209.165.201.2
209.165.201.1
209.165.200.230
Web Server
209.165.200.225
A user on the outside network requests a web page from the inside web server.
The ASA 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 ASA first classifies the packet to a context.
The ASA records that a session is established.
If the destination MAC address is in its table, the ASA forwards the packet out of the inside
interface. The destination MAC address is that of the downstream router, 209.165.201.1.
If the destination MAC address is not in the ASA table, the ASA attempts to discover the MAC
address by sending an ARP request and a ping. The first packet is dropped.
The web server responds to the request; because the session is already established, the packet
bypasses the many lookups associated with a new connection.
The ASA forwards the packet to the outside user.
Management IP
209.165.201.6
Cisco ASA Series CLI Configuration Guide
Firewall Mode Examples
Figure 1-11):
1-23