Configuring IP SLAs DNS Operations

Last Updated: July 18, 2011

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 feature information and caveats, see 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 document.

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 Router 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 Router 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:

Router> enable

 

Enables privileged EXEC mode.

  • Enter your password if prompted.
 
Step 2
configure terminal


Example:

Router# configure terminal

 

Enters global configuration mode.

 
Step 3
ip sla operation-number


Example:

Router(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:

Router(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:

Router(config-ip-sla-dns)# frequency 60

 

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

 
Step 6
end


Example:

Router(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:

Router> enable

 

Enables privileged EXEC mode.

  • Enter your password if prompted.
 
Step 2
configure terminal


Example:

Router# configure terminal

 

Enters global configuration mode.

 
Step 3
ip sla operation-number


Example:

Router(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:

Router(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:

Router(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:

Router(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:

Router(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:

Router(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:

Router(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:

Router(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:

Router(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:

Router(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:

Router(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:

Router(config-ip-sla-dns)# tag TelnetPollServer1

 

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

 
Step 15
threshold milliseconds


Example:

Router(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:

Router(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:

Router(config-ip-sla-dns)# end

 

Exits to privileged EXEC mode.

 

Scheduling IP SLAs Operations


Note
  • All IP SLAs operations to be scheduled must be already configured.
  • The frequency of all operations scheduled in a multioperation group must be the same.
  • List of one or more operation ID numbers to be added to a multioperation group is limited to a maximum of 125 characters, including commas (,).
SUMMARY STEPS

1.    enable

2.    configure terminal

3.    Do one of the following:

  • 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 [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.    exit

5.    show ip sla group schedule

6.    show ip sla configuration


DETAILED STEPS
  Command or Action Purpose
Step 1
enable


Example:

Router> enable

 

Enables privileged EXEC mode.

  • Enter your password if prompted.
 
Step 2
configure terminal


Example:

Router# configure terminal

 

Enters global configuration mode.

 
Step 3
Do one of the following:
  • 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 [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:

Router(config)# ip sla schedule 10 start-time now life forever



Example:

Router(config)# ip sla group schedule 1 3,4,6-9

 

For individual IP SLAs operations only:

Configures the scheduling parameters for an individual IP SLAs operation.

or

For multioperation scheduler only:

Specifies an IP SLAs operation group number and the range of operation numbers to be scheduled in global configuration mode.

 
Step 4
exit


Example:

Router(config)# exit

 

Exits to privileged EXEC mode.

 
Step 5
show ip sla group schedule


Example:

Router# show ip sla group schedule

 

(Optional) Displays the IP SLAs group schedule details.

 
Step 6
show ip sla configuration


Example:

Router# show ip sla configuration

 

(Optional) Displays the IP SLAs configuration details.

 

Troubleshooting Tips

  • If the IP SLAs operation is not running and generating statistics, add the verify-data command to the configuration of the operation (while configuring in IP SLA configuration mode) to enable data verification. When 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 debugipsla 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 SLAs operation, see the "Configuring Proactive Threshold Monitoring" section.

To view and interpret the results of an IP SLAs operation use the show ip sla statistics command. Checking the output for fields that correspond to criteria in your service level agreement will help you determine whether the service metrics are acceptable.

Configuration Examples for IP SLAs DNS Operations

Example Configuring a DNS Operation

The following example shows how to configure a DNS operation from Router B to the DNS server (IP address 172.20.2.132) as shown in the "DNS Operation" figure in the "DNS peration" 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.

Router 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

Cisco IOS IP SLAs: general information

Configuring IOS IP SLAs Overview chapter of the Cisco IOS IP SLAs Configuration Guide

Standards

Standards

Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

--

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

RFCs

RFCs

Title

No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.

--

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 Operations

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

12.2(31)SB2

12.2(33)SRB1

12.2(33)SXH

12.3(14)T

15.0(1)S

Cisco IOS XE 3.1.0SG

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

Cisco and the Cisco Logo are trademarks of Cisco Systems, Inc. and/or its affiliates in the U.S. and other countries. A listing of Cisco's trademarks can be found at www.cisco.com/go/trademarks. Third party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1005R)

Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.