Configuring DHCP Operations

Configuring IP SLAs DHCP Operations

Last Updated: March 22, 2011

This module describes how to configure an IP Service Level Agreements (SLAs) Dynamic Host Control Protocol (DHCP) operation to measure the response time between a Cisco device and a DHCP server to obtain an IP address.

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 http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Information About IP SLAs DHCP Operations

DHCP Operation

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

You can use the RTT information to determine DHCP performance levels.

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, discovery packets are sent only to the specified DHCP server.

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 IP SLAs DHCP Operations


Note


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

Configuring a DHCP Operation on the Source Device

Perform one of the following tasks:

Configuring a Basic DHCP Operation

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.    end


DETAILED STEPS
 Command or ActionPurpose
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 end


Example:
Router(config-ip-sla-dhcp)# end 
 

Exits to privileged EXEC mode.

 

Configuring a DHCP Operation with Optional Parameters

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.    end


DETAILED STEPS
 Command or ActionPurpose
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 end


Example:
Router(config-ip-sla-dhcp)# 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 ActionPurpose
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 DHCP Operations

Example Configuration for an IP SLAs DHCP Operation

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

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 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 DHCP 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 http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Table 1 Feature Information for IP SLAs DHCP Operations

Feature Name

Releases

Feature Information

IP SLAs DHCP 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 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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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.