• SonicOS 7.1 Rules and Policies
• Overview
  • About SonicOS
  • SonicOS Workflow
  • How to Use the SonicOS Administration Guides
  • Guide Conventions
• Settings
  • Configuring App/Match/Malware
  • Configuring Content Filtering Service (CFS)
    • SonicWall CFS
    • CFS Custom Category
  • Geo-IP
    • Custom List
      • Editing a Custom List Entry
      • Deleting Custom List Entries
    • Using Geo-IP Diagnostics
  • Botnet
    • Configuring Botnet Settings
    • Creating Custom Botnet Lists
    • Viewing Dynamic Botnets Lists
    • Configuring a Dynamic Botnet List Server
    • Using Botnet Diagnostics
  • Decryption (DPI-SSL)
    • Certificate
    • Common Name
    • SSL Servers
  • Decryption (DPI-SSH)
  • Signature Update
• Security Policy
  • User & Country
  • App/URL/Custom Match
• NAT Policy
  • About NAT in SonicOS
  • About NAT Load Balancing
    • Determining the NAT LB Method to Use
    • Caveats
    • How Load Balancing Algorithms are Applied
    • Sticky IP Algorithm Examples
      • Example One - Mapping to a Network
      • Example Two - Mapping to an IP Address Range
  • About NAT64
    • Use of Pref64::/n
  • About FQDN-based NAT
  • About Source MAC Address Override
  • Viewing NAT Policy Entries
    • Changing the Display
    • Filtering the Display
  • Adding or Editing NAT or NAT64 Rule Policies
  • Deleting NAT Policies
  • Creating NAT Rule Policies: Examples
    • Creating a One-to-One NAT Policy for Inbound Traffic
    • Creating a One-to-One NAT Policy for Outbound Traffic
    • Inbound Port Address Translation via One-to-One NAT Policy
    • Inbound Port Address Translation via WAN IP Address
    • Creating a Many-to-One NAT Policy
    • Creating a Many-to-Many NAT Policy
    • Creating a NAT Load Balancing Policy for Two Web Servers
• Routing
  • About Routing
    • About Metrics and Administrative Distance
      • About Metrics
      • About Administrative Distance
    • Route Advertisement
    • ECMP Routing
    • Policy-based Routing
    • Policy-based TOS Routing
    • PBR Metric-based Priority
    • Policy-based Routing and IPv6
    • OSPF and RIP Advanced Routing Services
      • About Routing Services
        • Protocol Type
        • Maximum Hops
        • Split-Horizon
        • Poison Reverse
        • Routing Table Updates
        • Subnet Sizes Supported
        • Autonomous System Topologies
      • OSPF Terms
    • Drop Tunnel Interface
    • App-based Routing
  • Rules and Policies >
    • Configuring
      • Adding Static Routes
      • Probe-Enabled Policy-based Routing Configuration
• Decryption Policy
  • Client-side SSL Rules
  • Server-side SSL Rules
  • SSH Rules
  • Setting up the Decryption Policy Table
    • Managing the Decryption Policy Toolbars
    • Changing the Policy Priority
    • Creating Decryption Policies
      • Adding Decryption Policies
      • Editing Decryption Policies
      • Deleting Decryption Policies
• DoS Policy
  • Setting up the DoS Policy Table
    • Managing the DoS Policy Toolbars
    • Changing the DoS Policy Priority
    • Creating DoS Policies
      • Adding DoS Policies
      • Editing DoS Policies
      • Deleting DoS Policies
• DNS Policy
  • Creating DNS Policies
    • Adding DNS Policies
    • Editing DNS Policies
    • Deleting DNS Policies
  • DNS Doctoring
• Endpoint Policy
• Shadow
• SonicWall Support
  • About This Document

DNS Doctoring

Introduction

DNS Doctoring allows the firewall to change the embedded IP addresses in Domain Name System (DNS) responses so that clients can connect to the correct IP address of servers. Specifically, DNS Doctoring performs two functions:

• Translates a public address in a DNS reply to a private address when the DNS client is on a private interface.
• Translates a private address to a public address when the DNS client is on the public interface.

Configuring DNS Doctoring

There are two kinds of situations that in which we need to use the DNS Doctoring feature.

The first one is shown in the Client Internal graphic. In this scenario, the local client and the local application server are both located on the inside interface of our appliance, while the DNS server that the client uses is located on another public network. When the client wants to access the server with its URL, the DNS server would return the public address of the application server to the client. So the client can’t access the local server with its public address.

Client Internal

Client External shows the second situation. The DNS server and application server are located on the inside interface of our appliance. When the external client tries to access the application server, the DNS server that the client uses would hand out the private address. But the external cannot access to the server with its private address.

Client External