Configuring Cisco IOS IP SLAs DNS Operations

First Published: August 14, 2006
Last Updated: January 6, 2011

This module describes how to configure the Cisco IOS 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 for IP SLAs DNS Operations" section.

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

Contents

•Information About IP SLAs DNS Operations

•How to Configure IP SLAs DNS Operations

•Configuration Examples IP SLAs DNS Operations

•Additional References

•Feature Information for IP SLAs DNS Operations

Information About IP SLAs DNS Operations

•DNS Operation

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 Figure 1 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 (required)

•Scheduling IP SLAs Operations (required)

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

•Configuring a DNS Operation with Optional Parameters on the Source Device

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

Restrictions

•The frequency of all operations scheduled in a multioperation group must be the same.

•Operation ID numbers are limited to a maximum of 125 characters. Do not give large integer values as operation ID numbers.

SUMMARY STEPS

1. enable

2. configure terminal

For individual IP SLAs operations only:

3. 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]

For multioperation scheduler only:

4. 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}]

5. exit

6. show ip sla group schedule

7. 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 

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]

Example:

Router(config)# ip sla schedule 11 start-time now life forever

For individual IP SLAs operations only:

Configures the scheduling parameters for an individual IP SLAs operation.

Step 4  

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 group schedule 1 3,4,6-9

For multioperation scheduler only:

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

•The frequency of all operations scheduled in the operation group should be the same.

•The operation ID numbers are limited to a maximum of 125 characters. Do not use large integer values as operation ID numbers.

Step 5 

exit

Example:

Router(config)# exit

Exits to privileged EXEC mode.

Step 6 

show ip sla group schedule

Example: 
Router# show ip sla group schedule

(Optional) Displays the IP SLAs group schedule details.

Step 7  

show ip sla configuration
Example: 
Router# show ip sla configuration

(Optional) Displays the IP SLAs configuration details.

Examples

The following sample output shows the configuration of all the IP SLAs parameters (including defaults) for the DNS operation number 11. 

Router# show ip sla configuration 11


Complete Configuration Table (includes defaults)

Entry number: 11

Owner: DNS-Test

Tag: DNS-Test

Type of operation to perform: dns

Target address: www.cisco.com

Source address: 0.0.0.0

Source port: 0

Operation timeout (milliseconds): 9000

Operation frequency (seconds): 60

Next Scheduled Start Time: Start Time already passed

Group Scheduled: FALSE

Life (seconds): Forever

Entry Ageout (seconds): never

Recurring (Starting Everyday): FALSE

Status of entry (SNMP RowStatus): Active

Threshold (milliseconds): 5000

Number of statistic hours kept: 2

Number of statistic distribution buckets kept: 1

Statistic distribution interval (milliseconds): 20

Number of history Lives kept: 0

Number of history Buckets kept: 15

History Filter Type: None

Troubleshooting Tips

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 SLAs operation, see Configuring Proactive Threshold Monitoring.

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 IP SLAs DNS Operations

•Example: Configuring a DNS Operation

Example: Configuring a DNS Operation

The following example shows how to configure a DNS operation as shown in Figure 1 from Router B to the DNS server (IP address 172.20.2.132). 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

"Cisco IOS IP SLAs Overview" chapter of the Cisco 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

Table 1 lists the features in this module and provides links to specific configuration information.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Note Table 1 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.

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.


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

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