Cisco ASA 5505 - Manual (Page 603)

30-21
Cisco ASA 5500 Series Configuration Guide using the CLI
Chapter 30 Configuring Network Object NAT
Configuration Examples for Network Object NAT
DNS Server and Web Server on Mapped Interface, Web Server is Translated
(Static NAT with DNS Modification)
Figure 30-6 shows a web server and DNS server on the outside. The ASA has a static translation for the
outside server. In this case, when an inside user requests the address for ftp.cisco.com from the DNS
server, the DNS server responds with the real address, 209.165.20.10. Because you want inside users to
use the mapped address for ftp.cisco.com (10.1.2.56) you need to configure DNS reply modification for
the static translation.
Figure 30-6 DNS Reply Modification Using Outside NAT
Step 1 Create a network object for the FTP server address:
hostname(config)# object network FTP_SERVER
Step 2 Define the FTP server address, and configure static NAT with DNS modification:
hostname(config-network-object)# host 209.165.201.10
hostname(config-network-object)# nat (outside,inside) static 10.1.2.56 dns
ftp.cisco.com
209.165.201.10
DNS Server
Outside
Inside
User
10.1.2.27
Static Translation on Inside to:
10.1.2.56
130022
1
2
7
6
5
4
3
DNS Query
ftp.cisco.com?
DNS Reply
209.165.201.10
DNS Reply Modification
209.165.201.10 10.1.2.56
DNS Reply
10.1.2.56
FTP Request
209.165.201.10
Dest Addr. Translation
209.165.201.10 10.1.2.56
FTP Request
10.1.2.56
Security
Appliance