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Cisco ASA Series Firewall CLI Configuration Guide
Chapter4 Configuring Network Object NAT
Configuration Examples for Network Object NAT
IPv4 DNS Server and FTP Server on Mapped Interface, IPv6 Host on Real Interface (Static NAT64 with DNS64 Modification)

Figure 4-6 shows an FTP server and DNS server on the outside IPv4 network. The ASA has a static

translation for the outside server. In this case, when an inside IPv6 user requests the address for

ftp.cisco.com from the DNS server, the DNS server responds with the real address, 209.165.200.225.

Because you want inside users to use the mapped address for ftp.cisco.com (2001:DB8::D1A5:C8E1)

you need to configure DNS reply modification for the static translation. This example also includes a

static NAT translation for the DNS server, and a PAT rule for the inside IPv6 hosts.

Figure4-7 DNS Reply Modification Using Outside NAT
Step1 Configure static NAT with DNS modification for the FTP server.
a. Create a network object for the FTP server address.
ciscoasa(config)# object network FTP_SERVER
b. Define the FTP server address, and configure static NAT with DNS modification and, because this

is a one-to-one translation, configure the net-to-net method for NAT46.

ciscoasa(config-network-object)# host 209.165.200.225
ciscoasa(config-network-object)# nat (outside,inside) static 2001:DB8::D1A5:C8E1/128
net-to-net dns
ftp.cisco.com
209.165.200.225
IPv4 Internet
IPv6 Net
Static Translation on Inside to:
2001:DB8::D1A5:C8E1
PAT Translation on Outside to:
209.165.200.230
User:
2001:DB8::1
DNS Server
209.165.201.15
Static Translation on Inside to:
2001:DB8::D1A5:C90F
1
2
7
6
5
4
3
DNS Query
ftp.cisco.com?
DNS Reply
209.165.200.225
DNS Reply Modification
209.165.200.225 2001:DB8::D1A5:C8E1
DNS Reply
2001:DB8::D1A5:C8E1
FTP Request
209.165.200.225
Dest Addr. Translation
209.165.200.2252001:DB8::D1A5:C8E1
FTP Request
2001:DB8::D1A5:C8E1
ASA
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