Cisco CSS 11000 Series Content Services Switches

DNS Forwarder on the CSS 11000 Configuration Example

Document ID: 25841

Updated: Jan 31, 2006



You can configure the Cisco Content Services Switch (CSS) 11000 with Address records (A records) and Name Service (NS) records, but not with Mail Exchange (MX) records. If your design requires the CSS to respond to MX records, you can use a Domain Name System (DNS) forwarder to configure the CSS.

The forwarder receives DNS requests that the CSS cannot resolve or that contain a request or record type without support. The forwarder sends DNS responses to the client transparently through the CSS. An internal keepalive mechanism sends queries periodically to validate the state of the forwarder and monitor forwarder health.



There are no specific requirements for this document.

Components Used

This document is not restricted to specific software and hardware versions.


For more information on document conventions, refer to the Cisco Technical Tips Conventions.


In this section, you are presented with the information to configure the features described in this document.

Note: To find additional information on the commands used in this document, use the Command Lookup Tool (registered customers only) .

In order to configure the forwarder, you must configure and enable a DNS server zone on the CSS.

Step-by-Step Instructions

Perform these steps:

  1. Issue this command:

    (config)# dns-server zone 0 tier1 dns forwarder example
  2. Issue this command:

    (config)# dns-server forwarder primary 
  3. Issue this command:

    (config)# dns-server


This section provides information that you can use to confirm that your configuration works properly.

Certain show commands are supported by the Output Interpreter Tool (registered customers only) , which allows you to view an analysis of show command output.

  • Issue the show running-config global command to verify the changes that you have made.

    (config)# show running-config global 
    !*************************** GLOBAL *************************** 
      dns-server zone 0 tier1 "dns forwarder example" 
      dns-server forwarder primary 
       ip route 1 
  • Issue the nslookup command to test the DNS forwarder.

    Point nslookup to the circuit IP address of the CSS.

    O:\> nslookup
    Default Server: 
    > server
    Default Server:  [] 
    Server:  [] 
  • Issue the show dns-server forwarder command to view the state of the forwarder.

    The command also provides the number of requests that the forwarder sent and the number of responses that the forwarder accepted.

    CSS-50(config)# show dns-server forwarder 
    DNS Server Forwarder Primary:   Up 
      State Changes:                     1 
      Requests Sent:                     4 
      Responses Accepted:           4 
    DNS Server Forwarder Secondary: Not Configured 
      State Changes:                     0 
      Requests Sent:                     0 
      Responses Accepted:           0 
      Requests Sent:                     4 
      Responses Accepted:           4 


There is currently no specific troubleshooting information available for this configuration.

Related Information

Updated: Jan 31, 2006
Document ID: 25841