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IP SLAs -- Analyzing IP Service Levels Using the DNS Operation

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Table Of Contents

IP SLAs—Analyzing IP Service Levels Using the DNS Operation

Finding Feature Information

Contents

Prerequisites for the IP SLAs DNS Operation

Information About the IP SLAs DNS Operation

DNS Operation

How to Configure the IP SLAs DNS Operation

Configuring and Scheduling a DNS Operation on the Source Device

Configuring and Scheduling a Basic DNS Operation on the Source Device

Configuring and Scheduling a DNS Operation with Optional Parameters on the Source Device

Configuration Examples for the IP SLAs DNS Operation

Configuring a DNS Operation: Example

Where to Go Next

Additional References

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Feature Information for the IP SLAs DNS Operation


IP SLAs—Analyzing IP Service Levels Using the DNS Operation

First Published: August 14, 2006
Last Updated: July 16, 2008

This module describes how to use the Cisco IOS IP Service Level Agreements (SLAs) DNS operation to measure the difference between the time taken to send a Domain Name System (DNS) request and receive a reply. IP SLAs is a portfolio of technology embedded in most devices that run Cisco IOS software, which allows Cisco customers to analyze IP service levels for IP applications and services, to increase productivity, to lower operational costs, and to reduce the frequency of network outages. IP SLAs uses active traffic monitoring—the generation of traffic in a continuous, reliable, and predictable manner—for measuring network performance. 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 the IP SLAs DNS Operation" section.

Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS 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

•Prerequisites for the IP SLAs DNS Operation

•Information About the IP SLAs DNS Operation

•How to Configure the IP SLAs DNS Operation

•Configuration Examples for the IP SLAs DNS Operation

•Where to Go Next

•Additional References

•Feature Information for the IP SLAs DNS Operation

Prerequisites for the IP SLAs DNS Operation

Before configuring the IP SLAs DNS operation you should be familiar with the "Cisco IOS IP SLAs Overview" chapter of the Cisco IOS IP SLAs Configuration Guide.

Information About the IP SLAs DNS Operation

To perform the tasks required to analyze DNS lookup times using IP SLA, you should understand the following concept:

•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 the IP SLAs DNS Operation

This section contains the following procedure:

•Configuring and Scheduling a DNS Operation on the Source Device (required)

Configuring and Scheduling a DNS Operation on the Source Device

To measure the difference between the time taken to send a DNS request and the time a reply is received by a Cisco device, use the IP SLAs DNS operation. This operation does not require the IP SLAs Responder to be enabled so there are no tasks to be performed on the destination device.

Perform one of the following tasks in this section, depending on whether you want to configure a basic DNS operation or configure a DNS operation with optional parameters:

•Configuring and Scheduling a Basic DNS Operation on the Source Device

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

Configuring and Scheduling a Basic DNS Operation on the Source Device

Perform this task to enable a DNS operation without any optional parameters.

Note For information on scheduling a group of operations, see the "IP SLAs—Multioperation Scheduling of IP SLAs Operations" chapter of the Cisco IOS IP SLAs Configuration Guide.

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. exit

7. 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]

8. exit

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 

exit

Example:

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

Exits DNS configuration submode and returns to global configuration mode.

Step 7 

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 10 start-time now life forever

Configures the scheduling parameters for an individual IP SLAs operation.

Step 8 

exit

Example:

Router(config)# exit

(Optional) Exits global configuration mode and returns to privileged EXEC mode.

Examples

The following example shows the configuration of an IP SLAs operation type of DNS to find the IP address of the hostname host1. The DNS operation number 11 is scheduled to start immediately and run indefinitely. 

ip sla 11

 dns host1 name-server 172.20.2.132

 frequency 60

!

ip sla schedule 11 life forever start-time now

What to Do Next

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.

Configuring and Scheduling a DNS Operation with Optional Parameters on the Source Device

Perform this task to enable a DNS operation on the source device and configure some optional IP SLAs parameters. The source device is the location at which the measurement statistics are stored.

Note For information on scheduling a group of operations, see the "IP SLAs—Multioperation Scheduling of IP SLAs Operations" chapter of the Cisco IOS IP SLAs Configuration Guide.

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. exit

18. 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]

19. exit

20. show ip sla configuration [operation-number]

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 

exit

Example:

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

Exits DNS configuration submode and returns to global configuration mode.

Step 18 

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 10 start-time now life forever

Configures the scheduling parameters for an individual IP SLAs operation.

Step 19 

exit

Example:

Router(config)# exit

(Optional) Exits global configuration mode and returns to privileged EXEC mode.

Step 20 

show ip sla configuration [operation-number]

Example:

Router# show ip sla configuration 10

(Optional) Displays configuration values including all defaults for all IP SLAs operations or a specified operation.

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 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 the IP SLAs DNS Operation

This section contains the following configuration example:

•Configuring a DNS Operation: Example

Configuring a DNS Operation: Example

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

Where to Go Next

For information about other types of IP SLAs operations and IP SLAs features, see the Cisco IOS IP SLAs Features Roadmap.

Additional References

The following sections provide references related to the IP SLAs DNS operation.

Related Documents

Related Topic
Document Title

Cisco IOS IP SLAs command-line interface enhancements

Cisco IOS IP Service Level Agreements Command Line Interface, Cisco white paper

Cisco IOS IP SLAs commands

Cisco IOS IP SLAs Command Reference


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

Technical Assistance Center (TAC) home page, containing 30,000 pages of searchable technical content, including links to products, technologies, solutions, technical tips, and tools. Registered Cisco.com users can log in from this page to access even more content.

http://www.cisco.com/public/support/tac/home.shtml


Feature Information for the IP SLAs DNS Operation

Table 1 lists the release history for this feature.

Not all commands may be available in your Cisco IOS software release. For release information about a specific command, see the command reference documentation.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS and Catalyst OS 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 Cisco IOS software release that introduced support for a given feature in a given Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS 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

12.3(14)T, 12.2(31)SB2, 12.2(33)SRB1, 12.2(33)SXH, Cisco IOS XE Release 2.1

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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All other trademarks mentioned in this document or website 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. (0812R)

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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