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

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Table Of Contents

IP SLAs—Analyzing IP Service Levels Using the DHCP Operation

Finding Feature Information

Contents

Prerequisites for the IP SLAs DHCP Operation

Information About the IP SLAs DHCP Operation

DHCP Operation

IP SLAs DHCP Relay Agent Options

How to Configure the IP SLAs DHCP Operation

Configuring and Scheduling a DHCP Operation on the Source Device

Configuring and Scheduling a Basic DHCP Operation on the Source Device

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

Configuration Examples for the IP SLAs DHCP Operation

Configuring a DHCP Operation: Example

Where to Go Next

Additional References

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Feature Information for the IP SLAs DHCP Operation


IP SLAs—Analyzing IP Service Levels Using the DHCP 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) DHCP operation to measure the response time between a Cisco device and a Dynamic Host Control Protocol (DHCP) server to obtain an IP address. 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 DHCP operation can be displayed and analyzed to determine the DHCP response time within your network, or for a specific DHCP server. The DHCP operation can be used also for troubleshooting DHCP server performance.

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 DHCP 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 DHCP Operation

•Information About the IP SLAs DHCP Operation

•How to Configure the IP SLAs DHCP Operation

•Configuration Examples for the IP SLAs DHCP Operation

•Where to Go Next

•Additional References

•Feature Information for the IP SLAs DHCP Operation

Prerequisites for the IP SLAs DHCP Operation

Before configuring the IP SLAs DHCP 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 DHCP Operation

To perform the tasks required to analyze DHCP server response times using IP SLAs, you should understand the following concepts:

•DHCP Operation

•IP SLAs DHCP Relay Agent Options

DHCP Operation

The Dynamic Host Configuration Protocol (DHCP) operation measures the round-trip time (RTT) taken to discover a DHCP server and obtain a leased IP address from it. DHCP provides a mechanism for allocating IP addresses dynamically so that addresses can be reused when hosts no longer need them. IP SLAs releases the leased IP address after the operation.

There are two modes for the DHCP operation. By default, the DHCP operation sends discovery packets on every available IP interface on the router. If a specific server is configured on the router, using the ip dhcp-server command, discovery packets are sent only to that DHCP server.

The DHCP operation also measures your DHCP server performance levels by determining the RTT taken to obtain a leased IP address.

IP SLAs DHCP Relay Agent Options

A DHCP relay agent is any host that forwards DHCP packets between clients and servers. Relay agents are used to forward requests and replies between clients and servers when they are not on the same physical subnet. Relay agent forwarding is distinct from the normal forwarding of an IP router, where IP packets are switched between networks somewhat transparently. Relay agents receive DHCP messages and then generate a new DHCP message to send out on another interface.

The IP SLAs DHCP operation contains a relay agent information option—Option 82—which is inserted by the DHCP relay agent when forwarding client-originated DHCP packets to a DHCP server. Servers recognizing the relay agent information option may use the information to implement IP address or other parameter assignment policies. The DHCP server echoes the option back verbatim to the relay agent in server-to-client replies, and the relay agent strips the option before forwarding the reply to the client.

Option 82 includes three suboptions that convey information known by the relay agent:

•circuit-id—identifies the incoming circuit.

•remote-id—provides a trusted identifier for a remote high-speed modem.

•subnet-mask—identifies the mask of the logical IP subnet from which the relay agent received the client DHCP packet.

How to Configure the IP SLAs DHCP Operation

This section contains the following procedure:

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

Configuring and Scheduling a DHCP Operation on the Source Device

To measure the response time between a Cisco device and a DHCP server to lease an IP address, use the IP SLAs DHCP 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 DHCP operation or configure a DHCP operation with optional parameters:

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

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

Configuring and Scheduling a Basic DHCP Operation on the Source Device

Perform this task to enable a DHCP 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. dhcp {destination-ip-address | destination-hostname} [source-ip {ip-address | hostname}] [option-82 [circuit-id circuit-id] [remote-id remote-id] [subnet-mask subnet-mask]]

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 

dhcp {destination-ip-address | destination-hostname} [source-ip {ip-address | hostname}] [option-82 [circuit-id circuit-id] [remote-id remote-id] [subnet-mask subnet-mask]]

Example:

Router(config-ip-sla)# dhcp 10.10.10.3

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

Step 5 

frequency seconds

Example:

Router(config-ip-sla-dhcp)# frequency 30

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

Step 6 

exit

Example:

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

Exits IP SLA DHCP configuration mode 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 the global configuration mode and returns to privileged EXEC mode.

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 DHCP Operation with Optional Parameters on the Source Device

Perform this task to enable a DHCP 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. dhcp {destination-ip-address | destination-hostname} [source-ip {ip-address | hostname}] [option-82 [circuit-id circuit-id] [remote-id remote-id] [subnet-mask subnet-mask]]

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 

dhcp {destination-ip-address | destination-hostname} [source-ip {ip-address | hostname}] [option-82 [circuit-id circuit-id] [remote-id remote-id] [subnet-mask subnet-mask]]

Example:

Router(config-ip-sla)# dhcp 10.10.10.3 option-82 circuit-id 10005A6F1234

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

Step 5 

history buckets-kept size

Example:

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

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

Step 15 

threshold milliseconds

Example:

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

Exits DHCP 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 DHCP operation number 12. 

Router# show ip sla configuration 12


Complete Configuration Table (includes defaults)

Entry number: 12

Owner: DHCP-Test

Tag: DHCP-Test

Type of operation to perform: dhcp

Target address: 10.10.10.3

Source address: 0.0.0.0

Operation timeout (milliseconds): 5000

Dhcp option:

Operation frequency (seconds): 30

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 DHCP Operation

This section contains the following configuration example:

•Configuring a DHCP Operation: Example

Configuring a DHCP Operation: Example

In the following example, IP SLAs operation number 12 is configured as a DHCP operation enabled for DHCP server 172.16.20.3. Note that DHCP option 82 is used to specify the circuit ID.

Router B Configuration 

ip dhcp-server 172.16.20.3

!

ip sla 12

 dhcp 10.10.10.3 option-82 circuit-id 10005A6F1234

 frequency 30

 timeout 5000

 tag DHCP_Test

!

ip sla schedule 12 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 DHCP 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 DHCP 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 DHCP Operation 

Feature Name
Releases
Feature Information

IP SLAs DHCP 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 Dynamic Host Control Protocol (DHCP) operation allows you to schedule and measure the network response time between a Cisco device and a DHCP server to obtain an IP address.


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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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