DHCP Release and Renew CLI in EXEC Mode

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The DHCP Release and Renew CLI in EXEC Mode feature provides the ability to perform two

independent operations from the command-line interface (CLI):

• Immediately release a Dynamic Host Configuration Protocol (DHCP) lease for a DHCP client.

• Force a DHCP renewal of a lease for a DHCP client.

Feature History for the DHCP Release and Renew CLI in EXEC Mode Feature

Finding Support Information for Platforms and Cisco IOS Software Images

Use Cisco Feature Navigator to find information about platform support and Cisco IOS software image

support. Access Cisco Feature Navigator at http://www.cisco.com/go/fn. You must have an account on

Cisco.com. If you do not have an account or have forgotten your username or password, click Cancel at

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Contents

• Prerequisites for DHCP Release and Renew CLI in EXEC Mode, page 2

• Restrictions for DHCP Release and Renew CLI in EXEC Mode, page 2

• Information About DHCP Release and Renew CLI in EXEC Mode, page 2

• How to Enable DHCP Release and Renew CLI in EXEC Mode, page 3

• Configuration Examples for DHCP Release and Renew CLI in EXEC Mode, page 4

• Additional References, page 5

• Command Reference, page 6

Release Modification

12.3(4)T This feature was introduced.

12.2(27)SBA This feature was integrated into Cisco IOS Release 12.2(27)SBA.

DHCP Release and Renew CLI in EXEC Mode

Prerequisites for DHCP Release and Renew CLI in EXEC Mode

Cisco IOS Release: Multiple releases (see the Feature History table)

Prerequisites for DHCP Release and Renew CLI in EXEC Mode

Before you use the DHCP Release and Renew CLI in EXEC Mode feature, the DHCP client must be

assigned an IP address by the DHCP server.

Restrictions for DHCP Release and Renew CLI in EXEC Mode

If the DHCP client is not assigned an IP address by the DHCP server, the DHCP Release and Renew CLI

commands will fail.

Information About DHCP Release and Renew CLI in EXEC Mode

Before using the DHCP Release and Renew CLI in EXEC Mode feature, you should understand the

following concepts:

• Benefits of the DHCP Release and Renew CLI in EXEC Mode Feature, page 2

• DHCP Release and Renew CLI Operation, page 2

Benefits of the DHCP Release and Renew CLI in EXEC Mode Feature

The DHCP Release and Renew CLI in EXEC Mode feature provides the ability to perform two

independent operations from the CLI:

• Immediately release a Dynamic Host Configuration Protocol (DHCP) lease for a DHCP client.

• Force a DHCP renewal of a lease for a DHCP client.

The DHCP Release and Renew CLI in EXEC Mode feature provides the following benefits:

• Eliminates the need to go into the configuration mode to reconfigure the router to release or renew

a DHCP lease.

• Simplifies the release and renewal of a DHCP lease.

• Reduces the amount of time spent performing DHCP IP release and renewal configuration tasks.

DHCP Release and Renew CLI Operation

Release a DHCP Lease

The release dhcp command starts the process to immediately release a DHCP lease for the specified

interface. After the lease is released, the interface address is deconfigured. The release dhcp command

does not deconfigure the ip address dhcp command specified in the configuration file for the interface.

During a write memory or show running configuration file action, or if the router is rebooted, the ip

address dhcp command executes to acquire a DHCP address for the interface.

The original IP address for the interface must be assigned by the DHCP server. If the interface is not

assigned an IP address by the DHCP server, the release dhcp command fails and displays the following

error message:

Interface does not have a DHCP originated address

DHCP Release and Renew CLI in EXEC Mode

How to Enable DHCP Release and Renew CLI in EXEC Mode

Cisco IOS Release: Multiple releases (see the Feature History table)

Renew a DHCP Lease

The renew dhcp command advances the DHCP lease timer to the next stage, at which point one of the

following occurs:

• If the lease is currently in a BOUND state, the lease is advanced to the RENEW state and a DHCP

RENEW request is sent.

• If the lease is currently in a RENEW state, the timer is advanced to the REBIND state and a DHCP

REBIND request is sent.

If there is no response to the RENEW request, the interface remains in the RENEW state. In this case,

the lease timer will advance to the REBIND state and subsequently send a REBIND request.

If a NAK response is sent in response to the RENEW request, the interface is deconfigured.

The original IP address for the interface must be assigned by the DHCP server. If the interface is not

assigned an IP address by the DHCP server, the renew dhcp command fails and displays the following

error message:

Interface does not have a DHCP originated address

How to Enable DHCP Release and Renew CLI in EXEC Mode

This section contains the following procedure:

• Enabling DHCP Release and Renew CLI in EXEC Mode, page 3 (required)

Enabling DHCP Release and Renew CLI in EXEC Mode

To enable the DHCP Release and Renew CLI in EXEC Mode feature, perform the following steps:

SUMMARY STEPS

1. enable

2. release dhcp type number

3. renew dhcp type number

DHCP Release and Renew CLI in EXEC Mode

Configuration Examples for DHCP Release and Renew CLI in EXEC Mode

Cisco IOS Release: Multiple releases (see the Feature History table)

DETAILED STEPS

Configuration Examples for DHCP Release and Renew CLI in

EXEC Mode

This section contains the following configuration examples:

• Release DHCP Lease: Example, page 4

• Renew DHCP Lease: Example, page 4

Release DHCP Lease: Example

In the following example, a DHCP release is performed on an interface that was originally assigned an

IP address by the DHCP server.

Router# release dhcp ethernet 3/1

In the following example, an attempt is made to release the DHCP lease on an interface that was not

originally assigned an IP address by the DHCP server.

Router# release dhcp ethernet 3/1

Interface does not have a DHCP originated address

In the following example, the release dhcp command is executed without specifying the type and

number arguments.

Router# release dhcp

Incomplete command.

Renew DHCP Lease: Example

In the following example, the DHCP lease is renewed on an interface that was originally assigned an IP

address by the DHCP server.

Router# renew dhcp ethernet 3/1

Command or Action Purpose

Step 1

enable

Example:

Router> enable

Enables privileged EXEC mode.

• Enter your password if prompted.

Step 2

release dhcp type number

Example:

Router# release dhcp ethernet 3/1

Performs an immediate release of the DHCP lease for the

interface and deconfigures the IP address for the interface.

Step 3

renew dhcp type number

Example:

Router# renew dhcp ethernet 3/1

Forces the DHCP timer to advance to the next stage, at

which point a subsequent action is taken: a DHCP

REQUEST packet is sent to renew or rebind the lease.

DHCP Release and Renew CLI in EXEC Mode

Additional References

Cisco IOS Release: Multiple releases (see the Feature History table)

In the following example, an attempt is made to renew the DHCP lease on an interface that was not

originally assigned an IP address by the DHCP server.

Router# renew dhcp ethernet 3/1

Interface does not have a DHCP originated address

In the following example, the renew dhcp command is executed without specifying the type and number

arguments.

Router# renew dhcp

Incomplete command.

Additional References

This section provides references related to the DHCP Release and Renew CLI in EXEC Mode feature.

Related Topic Document Title

Information about managing configuration files Cisco IOS Configuration Fundamentals and Network Management

Command Reference, Release 12.3 T

Commands for showing interface statistics

Cisco IOS Interface and Hardware Component Command

Reference, Release 12.3 T

DHCP commands Cisco IOS IP Command Reference, Volume 1 of 4: Addressing and

Services, Release 12.3 T

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 Link

No new or modified MIBs are supported by this

feature, and support for existing MIBs has not been

modified by this feature.

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

DHCP Release and Renew CLI in EXEC Mode

Command Reference

Cisco IOS Release: Multiple releases (see the Feature History table)

RFCs

Technical Assistance

Command Reference

This section documents new commands. All other commands used with this feature are documented in

the Cisco IOS Release 12.3 T command reference publications.

• release dhcp

• renew dhcp

RFCs Title

RFC 2131 Dynamic Host Configuration Protocol

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

DHCP Release and Renew CLI in EXEC Mode

release dhcp

Cisco IOS Release: Multiple releases (see the Feature History table)

release dhcp

To perform an immediate release of a Dynamic Host Configuration Protocol (DHCP) lease for an

interface, use the release dhcp command in user EXEC or privileged EXEC mode.

release dhcp type number

Syntax Description

Command Modes User EXEC

Privileged EXEC

Command History

Usage Guidelines The release dhcp command immediately releases the DHCP lease on the interface specified by the type

and number arguments. If the router interface was not assigned a DHCP IP address by the DHCP server,

the release dhcp command fails and displays the following error message:

Interface does not have a DHCP originated address

This command does not have a no form.

Examples The following example shows how to release a DHCP lease for an interface.

Router# release dhcp ethernet 3/1

Related Commands

type Interface type. For more information, use the question mark (?) online help

function.

number Interface or subinterface number. For more information about the numbering

syntax for your networking device, use the question mark (?) online help

function.

Release Modification

12.3(4)T This command was introduced.

12.2(27)SBA This command was integrated into Cisco IOS Release 12.2(27)SBA.

Command Description

ip address dhcp Specifies that the Ethernet interface acquires an IP address through

DHCP.

lease Configures the duration of the lease for an IP address that is assigned

from a Cisco IOS DHCP server to a DHCP client.

renew dhcp Forces the renewal of the DHCP lease for the specified interface.

show dhcp lease Displays the DHCP addresses leased from a server.

show interface Displays statistics for all interfaces configured on the router or access

server.

show ip dhcp binding Displays address bindings on the Cisco IOS DHCP server.

DHCP Release and Renew CLI in EXEC Mode

release dhcp

Cisco IOS Release: Multiple releases (see the Feature History table)

show ip interface Displays a summary of an interface’s IP information and status.

show running-config Displays the contents of the currently running configuration file or the

configuration for a specific interface.

show startup-config Displays the contents of the configuration file that will be used at the next

system startup.

Command Description

DHCP Release and Renew CLI in EXEC Mode

renew dhcp

Cisco IOS Release: Multiple releases (see the Feature History table)

renew dhcp

To perform an immediate renewal of a Dynamic Host Configuration Protocol (DHCP) lease for an

interface, use the renew dhcp command in user EXEC or privileged EXEC mode.

renew dhcp type number

Syntax Description

Command Modes User EXEC

Privileged EXEC

Command History

Usage Guidelines The renew dhcp command immediately renews the DHCP lease for the interface specified by the type

and number arguments. If the router interface was not assigned an IP address by the DHCP server, the

renew dhcp command fails and displays the following error message:

Interface does not have a DHCP originated address

This command does not have a no form.

Examples The following example shows how to renew a DHCP lease for an interface.

Router# renew dhcp Ethernet 3/1

Related Commands

type Interface type. For more information, use the question mark (?) online help

function.

number Interface or subinterface number. For more information about the numbering

syntax for your networking device, use the question mark (?) online help

function.

Release Modification

12.3(4)T This command was introduced.

12.2(27)SBA This command was integrated into Cisco IOS Release 12.2(27)SBA.

Command Description

ip address dhcp Specifies that the Ethernet interface acquires an IP address through

DHCP.

lease Configures the duration of the lease for an IP address that is assigned

from a Cisco IOS DHCP server to a DHCP client.

release dhcp Releases the DHCP lease on the specified interface.

show dhcp lease Displays the DHCP addresses leased from a server.

show interface Displays statistics for all interfaces configured on the router or access

server.

show ip dhcp binding Displays address bindings on the Cisco IOS DHCP server.

DHCP Release and Renew CLI in EXEC Mode

renew dhcp

Cisco IOS Release: Multiple releases (see the Feature History table)

show ip interface Displays a summary of an interface’s IP information and status.

show running-config Displays the contents of the currently running configuration file or the

configuration for a specific interface.

show startup-config Displays the contents of the configuration file that will be used at the next

system startup.

Command Description

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