Domain name system 编辑

Domain Name System (DNS) translates human readable domain names to machine-readable IP addresses, and vice versa. Citrix SD-WAN provides the following DNS features:

• DNS Proxy
• DNS Transparent Forwarding

You can configure a DNS proxy or DNS transparent forwarding using the following two types of DNS service:

• Static DNS service: Intercepts the DNS requests destined to SD-WAN IP address and forwards it to the specified DNS servers. You can create internal, ISP, google or any other open source DNS service. Static DNS service can be configured at global and site level.

• Dynamic DNS service: Intercepts the DNS requests destined to SD-WAN IP address and redirects it to one of the DNS servers learned from the DHCP based WAN links. If the WAN link goes down another DHCP based WAN links DNS server is chosen. This feature is useful in the deployment where ISPs allow DNS requests only to DNS servers hosted by them. Dynamic DNS service can be configured at site level only. Only one dynamic DNS service is permitted per site.

DNS proxy

You can configure a proxy with multiple forwarders that helps steering DNS requests based on application domain names. DNS forwarding works for the requests that are received through UDP connections.

To configure SD-WAN as a DNS Proxy:

1. Define the domain name based applications. In the Configuration Editor, navigate to Global > Applications > Domain Name Based Applications.

   Enter the application name and the required domain names or patterns. You can group several domain names as an application. You can either enter the full domain name or use wild cards at the beginning. For example - *.google.com

   

2. Define the required DNS Services. You can define Static or Dynamic DNS service.

   To configure a Static DNS service, navigate to Global > DNS Service, select the Type as Static. Enter the Service Name and a pair of Primary and Secondary DNS server IP addresses.

   

   Note

   If you have configured Office 365 breakout policy, a Quad9 DNS service is auto created. For more information, see Office 365 Optimization.

   Alternatively, you can also define the Static DNS services at individual site level. The site-level DNS service configuration overrides the global configuration. To configure site-specific static DNS service, navigate to Sites > DNS > DNS Services and select the Type as Static.

   

   To configure a Dynamic DNS service, navigate to Sites > DNS > DNS Services and select the Type as Dynamic. Enter the Service Name and select Internet for Service Type and Service Instance.

   Note

   Dynamic DNS service can be configured at site level only. Only one dynamic DNS service is permitted per site.

   

3. Configure DNS proxy for the site. Navigate to Sites > DNS > DNS Proxy. Click +. Enter values for the following parameters:

   • DNS Proxy Name: Name of the DNS Proxy.
   • Default DNS Service: The default DNS Service to which the DNS requests are forwarded to, if none of the applications match in DNS forwarder look-up.
   • Interfaces: The interfaces on which the DNS requests are intercepted. Only trusted interfaces are allowed.
   • DNS Forwarders: List of DNS forwarders.
     • Order: The priority of the forwarder.
     • Application: Applications for which DNS requests have to be forwarded to the selected DNS service.
     • DNS Service: The DNS service that the DNS requests are forwarded to for the specified application.

     

DNS transparent forwarder

Citrix SD-WAN can be configured as a transparent DNS forwarder. In this mode, SD-WAN can intercept DNS requests that are not destined to its IP address and forward them to the specified DNS service. Only the DNS requests coming from local service on trusted interfaces are intercepted. If the DNS requests match any applications in the DNS forwarder list, then it is forwarded to the configured DNS service. DNS forwarding is supported only for requests coming over UDP connections.

To configure SD-WAN as a DNS transparent forwarder:

1. Navigate to Sites > DNS > DNS Transparent Forwarders. Click +.

2. Enter values for the following parameters:

   • Order: The priority of the forwarder.
   • Application: Applications for which DNS requests have to be forwarded to the selected DNS service.
   • DNS Service: The DNS service that the DNS requests are forwarded to for the specified application.

   

   Similarly, continue to add other DNS transparent forwarders as required.

3. Click Apply.

Monitoring

To view Proxy statistics and Transparent forwarder statistics, navigate to Monitoring > DNS. You can view the application name, DNS service name, DNS service status, and the number of hits to the DNS service.

Proxy Statistics

Transparent Forwarder Statistics