Cisco 7604 Configuration Guide - Page 437
Configuring DNS Rewrite with Two NAT Zones, static, access-group
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Chapter 22 Applying Application Layer Protocol Inspection DNS Inspection 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. Configuring DNS Rewrite with Two NAT Zones To implement a DNS Rewrite scenario similar to the one shown in Figure 22-4, perform the following steps: Step 1 Step 2 Step 3 Step 4 Step 5 Create a static translation for the web server, as follows: hostname(config)# static (inside,outside) mapped-address real-address netmask 255.255.255.255 dns where the arguments are as follows: • inside-The name of the inside interface of the FWSM. • outside-The name of the outside interface of the FWSM. • mapped-address-The translated IP address of the web server. • real-address-The real IP address of the web server. Create an access list that permits traffic to the port that the web server listens to for HTTP requests. hostname(config)# access-list acl-name permit tcp any host mapped-address eq port where the arguments are as follows: acl-name-The name you give the access-list. mapped-address-The translated IP address of the web server. port-The TCP port that the web server listens to for HTTP requests. Apply the access list created in Step 2 to the outside interface. To do so, use the access-group command, as follows. hostname(config)# access-group acl-name in interface outside If DNS inspection is disabled or if you want to change the maximum DNS packet length, configure DNS inspection. DNS application inspection is enabled by default with a maximum DNS packet length of 512 bytes. For configuration instructions, see the "Configuring DNS Inspection" section on page 22-24. On the public DNS server, add an A-record for the web server, such as: domain-qualified-hostname. IN A mapped-address where domain-qualified-hostname is the hostname with a domain suffix, as in server.example.com. The period after the hostname is important. mapped-address is the translated IP address of the web server. OL-20748-01 The following example configures the FWSM for the scenario shown in Figure 22-4. It assumes DNS inspection is already enabled. Example 22-2 DNS Rewrite with Two NAT Zones hostname(config)# static (inside,outside) 209.165.200.225 192.168.100.1 netmask 255.255.255.255 dns hostname(config)# access-list 101 permit tcp any host 209.165.200.225 eq www Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall Services Module Configuration Guide using ASDM 22-21
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