Configuring IP SLAs DNS Operations

This module describes how to configure the IP Service Level Agreements (SLAs) Domain Name System (DNS) operation to measure the difference between the time taken to send a DNS request and receive a reply. This module also demonstrates how the results of the DNS operation can be displayed and analyzed to determine the DNS lookup time which is a critical element for determining the performance of a DNS or web server.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

Information About IP SLAs DNS Operations

DNS Operation

The DNS operation measures the difference between the time taken to send a DNS request and receive a reply. DNS is used in the Internet for translating names of network nodes into addresses. The IP SLAs DNS operation queries for an IP address if you specify a host name, or queries for a host name if you specify an IP address.

In the figure below Device B is configured as the source IP SLAs device and a DNS operation is configured with the DNS server as the destination device.

Figure 1. DNS Operation

Connection response time is computed by measuring the difference between the time taken to send a request to the DNS server and the time a reply is received by Device B. The resulting DNS lookup time can help you analyze your DNS performance. Faster DNS lookup times translate to a faster web server access experience.

How to Configure IP SLAs DNS Operations

Configuring an IP SLAs DNS Operation on the Source Device


Note

There is no need to configure an IP SLAs responder on the destination device.

Perform one of the following tasks:

Configuring a Basic DNS Operation on the Source Device

SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    ip sla operation-number

    4.    dns {destination-ip-address | destination-hostname} name-server ip-address [source-ip {ip-address | hostname} source-port port-number]

    5.    frequency seconds

    6.    end


DETAILED STEPS
      Command or Action Purpose
    Step 1 enable


    Example: 
    Device> enable
     

    Enables privileged EXEC mode.

    • Enter your password if prompted.
     
    Step 2 configure terminal


    Example: 
    Device# configure terminal
     

    Enters global configuration mode.

     
    Step 3 ip sla operation-number


    Example: 
    Device(config)# ip sla 10
     

    Begins configuration for an IP SLAs operation and enters IP SLA configuration mode.

     
    Step 4 dns {destination-ip-address | destination-hostname} name-server ip-address [source-ip {ip-address | hostname} source-port port-number]


    Example: 
    Device(config-ip-sla)# dns host1 name-server 172.20.2.132
     

    Defines a DNS operation and enters IP SLA DNS configuration mode.

     
    Step 5 frequency seconds


    Example: 
    Device(config-ip-sla-dns)# frequency 60
     

    (Optional) Sets the rate at which a specified IP SLAs operation repeats.

     
    Step 6 end


    Example: 
    Device(config-ip-sla-dns)# end
     

    Exits to privileged EXEC mode.

     

    Configuring a DNS Operation with Optional Parameters on the Source Device

    SUMMARY STEPS

      1.    enable

      2.    configure terminal

      3.    ip sla operation-number

      4.    dns {destination-ip-address | destination-hostname} name-server ip-address [source-ip {ip-address | hostname} source-port port-number]

      5.    history buckets-kept size

      6.    history distributions-of-statistics-kept size

      7.    history enhanced [interval seconds] [buckets number-of-buckets]

      8.    history filter {none | all | overThreshold | failures}

      9.    frequency seconds

      10.    history hours-of-statistics-kept hours

      11.    history lives-kept lives

      12.    owner owner-id

      13.    history statistics-distribution-interval milliseconds

      14.    tag text

      15.    threshold milliseconds

      16.    timeout milliseconds

      17.    end


    DETAILED STEPS
        Command or Action Purpose
      Step 1 enable


      Example: 
      Device> enable
       

      Enables privileged EXEC mode.

      • Enter your password if prompted.
       
      Step 2 configure terminal


      Example: 
      Device# configure terminal
       

      Enters global configuration mode.

       
      Step 3 ip sla operation-number


      Example: 
      Device(config)# ip sla 10
       

      Begins configuration for an IP SLAs operation and enters IP SLA configuration mode.

       
      Step 4 dns {destination-ip-address | destination-hostname} name-server ip-address [source-ip {ip-address | hostname} source-port port-number]


      Example: 
      Device(config-ip-sla)# dns host1 name-server 172.20.2.132
       

      Defines a DNS operation and enters IP SLA DNS configuration mode.

       
      Step 5 history buckets-kept size


      Example: 
      Device(config-ip-sla-dns)# history buckets-kept 25
       

      (Optional) Sets the number of history buckets that are kept during the lifetime of an IP SLAs operation.

       
      Step 6 history distributions-of-statistics-kept size


      Example: 
      Device(config-ip-sla-dns)# history distributions-of-statistics-kept 5
       

      (Optional) Sets the number of statistics distributions kept per hop during an IP SLAs operation.

       
      Step 7 history enhanced [interval seconds] [buckets number-of-buckets]


      Example: 
      Device(config-ip-sla-dns)# history enhanced interval 900 buckets 100
       

      (Optional) Enables enhanced history gathering for an IP SLAs operation.

       
      Step 8 history filter {none | all | overThreshold | failures}


      Example: 
      Device(config-ip-sla-dns)# history filter failures
       

      (Optional) Defines the type of information kept in the history table for an IP SLAs operation.

       
      Step 9 frequency seconds


      Example: 
      Device(config-ip-sla-dns)# frequency 30
       

      (Optional) Sets the rate at which a specified IP SLAs operation repeats.

       
      Step 10 history hours-of-statistics-kept hours


      Example: 
      Device(config-ip-sla-dns)# history hours-of-statistics-kept 4
       

      (Optional) Sets the number of hours for which statistics are maintained for an IP SLAs operation.

       
      Step 11 history lives-kept lives


      Example: 
      Device(config-ip-sla-dns)# history lives-kept 5
       

      (Optional) Sets the number of lives maintained in the history table for an IP SLAs operation.

       
      Step 12 owner owner-id


      Example: 
      Device(config-ip-sla-dns)# owner admin
       

      (Optional) Configures the Simple Network Management Protocol (SNMP) owner of an IP SLAs operation.

       
      Step 13 history statistics-distribution-interval milliseconds


      Example: 
      Device(config-ip-sla-dns)# history statistics-distribution-interval 10
       

      (Optional) Sets the time interval for each statistics distribution kept for an IP SLAs operation.

       
      Step 14 tag text


      Example: 
      Device(config-ip-sla-dns)# tag TelnetPollServer1
       

      (Optional) Creates a user-specified identifier for an IP SLAs operation.

       
      Step 15 threshold milliseconds


      Example: 
      Device(config-ip-sla-dns)# threshold 10000
       

      (Optional) Sets the upper threshold value for calculating network monitoring statistics created by an IP SLAs operation.

       
      Step 16 timeout milliseconds


      Example: 
      Device(config-ip-sla-dns)# timeout 10000
       

      (Optional) Sets the amount of time an IP SLAs operation waits for a response from its request packet.

       
      Step 17 end


      Example: 
      Device(config-ip-sla-dns)# end
       

      Exits to privileged EXEC mode.

       

      Scheduling IP SLAs Operations

      Before You Begin
      • All IP Service Level Agreements (SLAs) operations to be scheduled must be already configured.
      • The frequency of all operations scheduled in a multioperation group must be the same.
      • The list of one or more operation ID numbers to be added to a multioperation group must be limited to a maximum of 125 characters in length, including commas (,).
      SUMMARY STEPS

        1.    enable

        2.    configure terminal

        3.    Enter one of the following commands:

        • ip sla schedule operation-number [life {forever | seconds}] [start-time {[hh:mm:ss] [month day | day month] | pending | now | after hh:mm:ss}] [ageout seconds] [recurring]
        • ip sla group schedule group-operation-number operation-id-numbers {schedule-period schedule-period-range | schedule-together} [ageout seconds] [frequency group-operation-frequency] [life {forever | seconds}] [start-time {hh:mm [:ss] [month day | day month] | pending | now | after hh:mm [:ss]}]

        4.    end

        5.    show ip sla group schedule

        6.    show ip sla configuration


      DETAILED STEPS
          Command or Action Purpose
        Step 1 enable


        Example: 
        Device> enable
         

        Enables privileged EXEC mode.

        • Enter your password if prompted.
         
        Step 2 configure terminal


        Example: 
        Device# configure terminal
         

        Enters global configuration mode.

         
        Step 3 Enter one of the following commands:
        • ip sla schedule operation-number [life {forever | seconds}] [start-time {[hh:mm:ss] [month day | day month] | pending | now | after hh:mm:ss}] [ageout seconds] [recurring]
        • ip sla group schedule group-operation-number operation-id-numbers {schedule-period schedule-period-range | schedule-together} [ageout seconds] [frequency group-operation-frequency] [life {forever | seconds}] [start-time {hh:mm [:ss] [month day | day month] | pending | now | after hh:mm [:ss]}]


        Example: 
        Device(config)# ip sla schedule 10 life forever start-time now
        Device(config)# ip sla group schedule 1 3,4,6-9 life forever start-time now
         
        • Configures the scheduling parameters for an individual IP SLAs operation.
        • Specifies an IP SLAs operation group number and the range of operation numbers for a multioperation scheduler.
         
        Step 4 end


        Example: 
        Device(config)# end
         

        Exits global configuration mode and returns to privileged EXEC mode.

         
        Step 5 show ip sla group schedule


        Example: 
        Device# show ip sla group schedule
         

        (Optional) Displays IP SLAs group schedule details.

         
        Step 6 show ip sla configuration


        Example: 
        Device# show ip sla configuration
         

        (Optional) Displays IP SLAs configuration details.

         

        Troubleshooting Tips

        • If the IP Service Level Agreements (SLAs) operation is not running and not generating statistics, add the verify-data command to the configuration (while configuring in IP SLA configuration mode) to enable data verification. When data verification is enabled, each operation response is checked for corruption. Use the verify-data command with caution during normal operations because it generates unnecessary overhead.
        • Use the debug ip sla trace and debug ip sla error commands to help troubleshoot issues with an IP SLAs operation.

        What to Do Next

        To add proactive threshold conditions and reactive triggering for generating traps (or for starting another operation) to an IP Service Level Agreements (SLAs) operation, see the “Configuring Proactive Threshold Monitoring” section.

        Configuration Examples for IP SLAs DNS Operations

        Example Configuring a DNS Operation

        The following example shows how to configure a DNS operation from Device B to the DNS server (IP address 172.20.2.132) as shown in the “DNS Operation” figure in the “DNS Operation” section. The operation is scheduled to start immediately. In this example, the target address is a hostname and the DNS operation will query the DNS server for the IP address associated with the hostname host1. No configuration is required at the DNS server.

        Device B Configuration

        ip sla 11
 dns host1 name-server 172.20.2.132
 frequency 50
 timeout 8000
 tag DNS-Test
ip sla schedule 11 start-time now

        Additional References

        Related Documents

        Related Topic

        Document Title

        Cisco IOS commands

        Cisco IOS Master Commands List, All Releases

        Cisco IOS IP SLAs commands

        Cisco IOS IP SLAs Command Reference, All Releases

        Cisco IOS IP SLAs: general information

        “Cisco IOS IP SLAs Overview” module of the Cisco IOS IP SLAs Configuration Guide.

        Multioperation scheduling for IP SLAs

        “Configuring Multioperation Scheduling of IP SLAs Operations” module of the Cisco IOS P SLAs Configuration Guide

        Proactive threshold monitoring for IP SLAs

        “Configuring Proactive Threshold Monitoring of IP SLAs Operations” module of the Cisco IOS IP SLAs Configuration Guide

        MIBs

        MIBs

        MIBs Link

        CISCO-RTTMON-MIB

        To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

        http:/​/​www.cisco.com/​go/​mibs

        Technical Assistance

        Description

        Link

        The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

        http:/​/​www.cisco.com/​cisco/​web/​support/​index.html

        Feature Information for IP SLAs - DNS Operation

        The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

        Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

        Table 1 Feature Information for the IP SLAs - DNS Operation

        Feature Name

        Releases

        Feature Information

        IP SLAs - DNS Operation

        Cisco IOS XE Release 3.2SE

        The IP SLAs Domain Name System (DNS) Operation feature allows you to measure the difference between the time taken to send a DNS request and receive a reply.