25-16
Cisco Security Appliance Command Line Configuration Guide
OL-12172-03
Chapter 25 Configuring Application Layer Protocol Inspection
DNS Inspection
•
Configuring DNS Rewrite with Two NAT Zones, page 25-16
•
DNS Rewrite with Three NAT Zones, page 25-17
•
Configuring DNS Rewrite with Three NAT Zones, page 25-19
For detailed syntax and additional functions for the
alias
,
nat
, and
static
command, see the appropriate
command page in the
Cisco Security Appliance Command Reference
.
Using the Static Command for DNS Rewrite
The
static
command causes addresses on an IP network residing on a specific interface to be translated
into addresses on another IP network on a different interface. The syntax for this command is as follows:
hostname(config)#
static (
real_ifc
,
mapped_ifc
)
mapped-address real-address
dns
The following example specifies that the address 192.168.100.10 on the inside interface is translated into
209.165.200.5 on the outside interface:
hostname(config)#
static (inside,outside) 209.165.200.225 192.168.100.10 dns
Note
Using the
nat
command is similar to using the
static
command except that DNS Rewrite is based on
dynamic translation instead of a static mapping.
Using the Alias Command for DNS Rewrite
The
alias
command causes the security appliance to translate addresses on an IP network residing on any
interface into addresses on another IP network connected through a different interface. The syntax for
this command is as follows:
hostname(config)#
alias (
interface_name
)
mapped-address real-address
The following example specifies that the real address (192.168.100.10) on any interface except the inside
interface will be translated to the mapped address (
209.165.200.225)
on the inside interface. Notice that
the location of 192.168.100.10 is not precisely defined.
hostname(config)#
alias (inside) 209.165.200.225 192.168.100.10
Note
If you use the
alias
command to configure DNS Rewrite, proxy ARP will be performed for the mapped
address. To prevent this, disable Proxy ARP by entering the
sysopt noproxyarp
command after entering
the
alias
command.
Configuring DNS Rewrite with Two NAT Zones
To implement a DNS Rewrite scenario similar to the one shown in
Figure 25-1
, perform the following
steps:
Step 1
Create a static translation for the web server, as follows:
hostname(config)#
static (
real_ifc
,
mapped_ifc
)
mapped-address real-address
netmask
255.255.255.255 dns
where the arguments are as follows:
Содержание 500 Series
Страница 38: ...Contents xxxviii Cisco Security Appliance Command Line Configuration Guide OL 12172 03 ...
Страница 45: ...P A R T 1 Getting Started and General Information ...
Страница 46: ......
Страница 277: ...P A R T 2 Configuring the Firewall ...
Страница 278: ......
Страница 354: ...17 38 Cisco Security Appliance Command Line Configuration Guide OL 12172 03 Chapter 17 Configuring NAT NAT Examples ...
Страница 561: ...P A R T 3 Configuring VPN ...
Страница 562: ......
Страница 891: ...P A R T 4 System Administration ...
Страница 892: ......
Страница 975: ...P A R T 5 Reference ...
Страница 976: ......