Cisco IOS IP Addressing Services Configuration Guide, Release 12.4T - Dynamic DNS Support for Cisco IOS Software [Cisco IOS Software Releases 12.4 T]

Table Of Contents

Dynamic DNS Support for Cisco IOS Software

Contents

Restrictions for Dynamic DNS Support for Cisco IOS Software

Information About Dynamic DNS Support for Cisco IOS Software

Domain Name System and Dynamic Updates

DDNS Updates for HTTP-Based Protocols

DHCP Support for DDNS Updates

Feature Design of Dynamic DNS Support for Cisco IOS Software

How to Configure Dynamic DNS Support for Cisco IOS Software

Configuring a Host List

Examples

Verifying the Host-List Configuration

Configuring DHCP Support of DDNS Updates

Prerequisites

Restrictions

Examples

Configuring DDNS Update Support on Interfaces

Prerequisites

Restrictions

Configuring a Pool of DHCP Servers to Support DDNS Updates

Prerequisites

Examples

Configuring the Update Method and Interval

Prerequisites

Examples

Verifying DDNS Updates

Configuration Examples for Dynamic DNS Support for Cisco IOS Software

Configuration of the DHCP Client: Example

Configuration of the DHCP Server: Example

Configuration of the HTTP Updates: Example

Additional References

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Command Reference

Dynamic DNS Support for Cisco IOS Software

The Dynamic DNS Support for Cisco IOS Software feature enables Cisco IOS software devices to perform Dynamic Domain Name System (DDNS) updates to ensure that an IP host DNS name is correctly associated with its IP address.

It provides two mechanisms to generate or perform DDNS: the IETF standard as defined by RFC 2136 and a generic HTTP using various DNS services. With this feature, you can define a list of hostnames and IP addresses that will receive updates, specify an update method, and specify a configuration for Dynamic Host Configuration Protocol (DHCP) triggered updates.

History for the Dynamic DNS Support for Cisco IOS Software Feature

Release

Modification

12.3(8)YA

This feature was introduced.

12.3(14)T

This feature was integrated into Cisco IOS Release 12.3(14)T.

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 the login dialog box and follow the instructions that appear.

Contents

•Restrictions for Dynamic DNS Support for Cisco IOS Software

•Information About Dynamic DNS Support for Cisco IOS Software

•How to Configure Dynamic DNS Support for Cisco IOS Software

•Configuration Examples for Dynamic DNS Support for Cisco IOS Software

•Additional References

•Command Reference

Restrictions for Dynamic DNS Support for Cisco IOS Software

The performance of the DHCP client can be impacted when the Dynamic DNS Support for Cisco IOS Software feature is enabled, because of sending DDNS update packets and waiting for responses from the server (before sending the ACK to the client REQUEST) and the client (immediately after receiving the ACK and assigning the address to the interface). The default for the client is two attempts with a 5-second wait time between attempts.

The DHCP server continues to process DHCP client DISCOVER and REQUEST packets while waiting for the DDNS updates to complete. Even if the update is done before sending the ACK to the client, it does not delay processing of other DHCP requests. The DHCP server could be impacted minimally because of the time and memory needed in order to set up the DDNS update and get things started.

Reloading the system may take a little longer in some cases, such as, if there are outstanding DDNS updates that need to complete.

Information About Dynamic DNS Support for Cisco IOS Software

To configure the Dynamic DNS Support for Cisco IOS Software, you should understand the following concepts:

•Domain Name System and Dynamic Updates

•DDNS Updates for HTTP-Based Protocols

•DHCP Support for DDNS Updates

•Feature Design of Dynamic DNS Support for Cisco IOS Software

Domain Name System and Dynamic Updates

The DNS was designed to support queries of a statically configured database. The data was expected to change, but minimally. All updates were made as external edits to a zone master file. The domain name identifies a node within the domain name space tree structure. Each node has a set (possibly empty) of Resource Records (RRs). All RRs having the same NAME, CLASS, and TYPE are called a Resource Record Set (RRset).

There are address (A) or forward RRs and pointer (PTR) or reverse RRs. The DDNS update can specify additions or deletions of hostnames and IP addresses. The two mechanisms to update this information are by using HTTP-based protocols such as DynDNS.org or by using the IETF standard.

DDNS Updates for HTTP-Based Protocols

The Dynamic DNS Support for Cisco IOS Software feature provides the capability of a proprietary HTTP-based protocol to generate or perform DDNS updates. The most notable HTTP-based protocol is DynDNS.org, but there are many others.

Since most of these protocols consist of a simple HTTP command that specifies parameters such as hostname and IP address in the URL portion of the command, this feature takes the same generic approach. You can specify the hostname and IP address in a URL. Configuration of a maximum interval between updates is also allowed.

DHCP Support for DDNS Updates

Before the Dynamic DNS Support for Cisco IOS Software feature, a DHCP server assigned IP addresses to DHCP clients and any DNS information was static. In a network that uses a DHCP server, there are many cases in which DNS hostnames should be associated with the IP addresses that are being assigned. There is an existing method for dynamically updating DNS for DHCP by using information in the fully qualified domain name (FQDN) DHCP option (if it is supplied by the client).

The Dynamic DNS Support for Cisco IOS Software feature enables the DHCP server to support a new FQDN DHCP option. In addition, when the address on an interface is configured, the client can pass the new FQDN option to the server so that name-to-address and address-to-name translations can be updated for the DHCP client as well.

Feature Design of Dynamic DNS Support for Cisco IOS Software

The Dynamic DNS Support for Cisco IOS Software feature enables the tracking of the FQDN DHCP option. If dynamic updates are enabled for the DHCP server, the server updates the PTR RR. The PTR RRs are used for reverse mapping (translation of addresses to names). PTRs use official names not aliases. The name in a PTR record is the local IP address portion of the reverse name.

If the client requests the server to update A RRs as well, the server will attempt to do it. The A RR provides the name-to-address mapping for a DNS zone. The server may be configured to override the client suggestion and always update PTR and A RRs.

The DHCP client can specify whether or not it wants to allow dynamic updates (include the FQDN option), instruct the server to allow the client to update both A and PTR RRs (normally only the A RR is updated by the client), and optionally instruct the server not to update any DNS information (either because the client will be updating both or simply because the client does not want the server to do any updates at all).

There are three basic components of the Dynamic DNS Support for Cisco IOS Software feature that are as follows:

•Definition of the hostname list and IP addresses that will receive updates using a new command that specifies a group of hostnames. Each configured list can consist of any number of IPv4 addresses or hostnames. If a hostname is configured, the name is translated to an IPv4 address at the time at which it is used.

•Specification of an update method. The options are HTTP, DDNS, or an internal Cisco IOS name cache. If the HTTP option is specified, the configuration will include a URL. The username and password must be explicitly written into the URL string and the entire "GET" operation must be specified on one line. The specification will be stored in a linked list. If the update method is DDNS, the configuration will include the update of the IP address.

Events that trigger updates can be as follows:

•IP address that is assigned by a DHCP server for an IP device

•IP address assigned to a router using a DHCP client

•Forwarding of the fully qualified domain name (FQDN) of a user or router hostname from the DHCP client to the server

•Point-to-Point Protocol (PPP)/IP Control Protocol (IPCP) obtaining an IP address for a router interface

•Forced update using a timer to verify a router IP address

Associated with each update method is a value specifying the maximum number of seconds between updates. If left unspecified, then the update is performed only when the address is changed. If specified, the update is performed automatically if the specified number of seconds have passed since the last update.

How to Configure Dynamic DNS Support for Cisco IOS Software

This section contains the following procedures:

•Configuring a Host List (optional)

•Verifying the Host-List Configuration (optional)

•Configuring DHCP Support of DDNS Updates (optional)

•Configuring DDNS Update Support on Interfaces (required)

•Configuring a Pool of DHCP Servers to Support DDNS Updates (optional)

•Configuring the Update Method and Interval (required)

•Verifying DDNS Updates (optional)

Note The internal Cisco IOS name cache does not require any configuration.

Configuring a Host List

Perform this task to configure a host list if you are going to use a host list in your configuration.

SUMMARY STEPS

1. enable

2. configure terminal

3. ip host-list host-list-name

4. host [vrf vrf-name] {host-ip-address | hostname}

5. 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 host-list host-list-name
Example:

Router(config)# ip host-list abc

Specifies a list of hosts and enters host-list configuration mode. The host-list-name argument assigns a name to the list of hosts.
Step 4
host [vrf vrf-name] {host-ip-address | hostname}
Example:
Router(host-list)# host 10.1.1.1 10.2.2.2 
10.3.3.3 a.com b.com 10.4.4.4 10.5.5.5 d.com 
host 10.6.6.6 f.com host vrf abc a.com b.com 
c.com host vrf def 10.1.1.1 10.2.2.2 10.3.3.3
Configures one or more hosts. The arguments and keyword are as follows:

•vrf vrf-name—Associates a hostname with a virtual private network (VPN) routing and forwarding instance (VRF) name.

Note All hostnames or IP addresses specified after the vrf keyword are associated with that VRF.

•host-ip-address—Specifies an IP address for a host in the host list. You can specify more than one host using this argument by listing the hostname and IP addresses on the same line.

•hostname—Specifies a hostname.
Step 5

exit
Example:

Router(config) exit

Exits to global configuration mode.
Examples

The following example shows how to configure several hosts with VRF:
ip host-list abc
 host 10.1.1.1 10.2.2.2 10.3.3.3 a.com b.com 10.4.4.4 10.5.5.5 d.com
 host 10.6.6.6 f.com
 host vrf abc a.com b.com c.com
 host vrf def 10.1.1.1 10.2.2.2 10.3.3.3
Verifying the Host-List Configuration

To verify the host-list configuration, perform the following steps.

SUMMARY STEPS

1. show ip host-list

2. show running-config | inc host-list

3. show running-config | inc host

4. debug ip ddns update

DETAILED STEPS

Step 1 show ip host-list

Use this command to verify that the IP addresses and hostnames have been assigned to a host list, for example:
Router# show ip host-list abc
Host list: abc
 ddns.abc
 10.2.3.4
 ddns2.abc
 10.3.4.5
 ddns3.com
 10.3.3.3
 d.org
 e.org
 1.org.2.org
 3.com
 10.2.2.2 (VRF: test)
 10.5.5.5 (VRF: test)
 a.net (VRF: test)
 b.net (VRF: test)
Step 2 show running-config | inc host-list

Use this command to verify the configuration of a host list, for example:
Router# show running-config | inc host-list
ip host-list a
ip host-list b
ip host-list c
ip host-list abc
Step 3 show running-config | inc host

Use this command to verify the configuration of a hostname, for example:
Router# show running-config | inc host
hostname who
ip host who 10.0.0.2
ip host-list a
 host 10.1.1.1 a.com b.com 10.2.2.3 10.2.2.2 c.com. 10.3.3.3 10.4.4.4
 host d.com
 host vrf abc 10.10.10.4 10.10.10.8
 host vrf def 10.2.3.4 10.6.7.8
ip host-list b
 host a.com b.com c.com 10.1.1.1 10.2.2.2 10.3.3.3
 host vrf ppp 10.2.1.0
ip host-list c
 host 10.1.1.1 10.2.2.2 10.3.3.3 a.com b.com 10.4.4.4 10.5.5.5 d.com
 host 10.6.6.6 f.com
 host vrf zero a.com b.com c.om
 host vrf one 10.1.1.1 10.2.2.2 10.3.3.3
ip host-list unit-test
 host ddns.unit.test 10.2.3.4 ddns2.unit.test 10.3.4.5 ddns3.com 10.3.3.3 d.org e.org
 host 1.org.2.org 3.com
 host vrf ZERO 10.2.2.2 10.5.5.5 a.net b.net
 ip ddns update hostname use-this.host.name
 ip ddns update this-method host 10.2.3.4
 ip ddns update this-method host this-host
 ip ddns update this-method host-group this-list
 ip ddns update this-method host 10.3.4.5
 ip ddns update test host 10.19.192.32
 ip ddns update test host 10.19.192.32
 ip ddns update a host-group a
 ip ddns update a host-group ab
 ip ddns update aa host-group ab
 ip ddns update method host 10.33.44.55
Step 4 debug ip ddns update

Use the debug ip ddns update command for the following configuration to verify the configuration of the hosts. Two servers are configured in the host list. A DHCP client is configured for IETF DDNS updating of both A and DNS RRs and requesting the DHCP server to update neither. The DHCP client is configured to include an FQDN DHCP option that instructs the DHCP server not to update either A or PTR Resource Records. This is configured using the interface version of the command. The DHCP server is configured to allow the DHCP client to update whatever RRs it chooses.
!Configure the DHCP Client
ip host-list servers
 host 10.19.192.32 10.0.0.1
ip ddns update method testing
 ddns
interface Ethernet1
 ip dhcp client update dns server none
 ip ddns update testing host-group servers
 ip address dhcp
end
!Configure the DHCP Server
ip dhcp pool test
 network 10.0.0.0 255.0.0.0
 update dns
!Enable Debugging
debug ip ddns update
!The update to the server 10.0.0.1 fails in this example
00:18:58:%DHCP-6-ADDRESS_ASSIGN: Interface Ethernet1 assigned DHCP address 10.0.0.8, mask 
255.0.0.0, hostname canada_reserved
00:18:58: DYNDNSUPD: Adding DNS mapping for canada_reserved.hacks <=> 10.0.0.8 server 
10.19.192.32
00:18:58: DYNDNSUPD: Sleeping for 3 seconds waiting for interface Ethernet1 configuration 
to settle
00:19:01: DDNS: Enqueuing new DDNS update 'canada_reserved.hacks' <=> 10.0.0.8 server 
10.19.192.32
00:19:01: DYNDNSUPD: Adding DNS mapping for canada_reserved.hacks <=> 10.0.0.8 server 
10.0.0.1
00:19:01: DDNS: Enqueuing new DDNS update 'canada_reserved.hacks' <=> 10.0.0.8 server 
10.0.0.1
00:19:01: DYNDNSUPD: Adding DNS mapping for canada_reserved.hacks <=> 10.0.0.8 server 
10.0.0.1
00:19:01: DDNS: Enqueuing new DDNS update 'canada_reserved.hacks' <=> 10.0.0.8 server 
10.0.0.1
00:19:01: DDNS: Zone name for '10.0.0.11.in-addr.arpa.' is '10.in-addr.arpa'
00:19:01: DDNS: Using server 10.19.192.32
00:19:01: DDNS: Dynamic Update 1: (sending to server 10.19.192.32)
00:19:01: DDNS: Zone = 10.in-addr.arpa
00:19:01: DDNS: Prerequisite: 10.0.0.11.in-addr.arpa. not in use
00:19:01: DDNS: Update: add 10.0.0.11.in-addr.arpa. IN PTR canada_reserved.hacks
00:19:01: DDNS: Zone name for '10.0.0.11.in-addr.arpa.' is '10.in-addr.arpa'
00:19:01: DDNS: Using server 10.0.0.1
00:19:01: DDNS: Dynamic Update 1: (sending to server 10.0.0.1)
00:19:01: DDNS: Zone = 10.in-addr.arpa
00:19:01: DDNS: Prerequisite: 10.0.0.11.in-addr.arpa. not in use
00:19:01: DDNS: Update: add 10.0.0.11.in-addr.arpa. IN PTR canada_reserved.hacks
00:19:01: DDNS: Zone name for '10.0.0.11.in-addr.arpa.' is '10.in-addr.arpa'
00:19:01: DDNS: Using server 10.0.0.1
00:19:01: DDNS: Dynamic Update 1: (sending to server 10.0.0.1)
00:19:01: DDNS: Zone = 10.in-addr.arpa
00:19:01: DDNS: Prerequisite: 10.0.0.11.in-addr.arpa. not in use
00:19:01: DDNS: Update: add 10.0.0.11.in-addr.arpa. IN PTR canada_reserved.hacks
00:19:01: DDNS: Dynamic DNS Update 1 (PTR) for host canada_reserved.hacks returned 6 
(YXDOMAIN)
00:19:01: DDNS: Dynamic Update 2: (sending to server 10.19.192.32)
00:19:01: DDNS: Zone = 10.in-addr.arpa
00:19:01: DDNS: Update: delete 10.0.0.11.in-addr.arpa. all PTR RRs
00:19:01: DDNS: Update: add 10.0.0.11.in-addr.arpa. IN PTR canada_reserved.hacks
00:19:01: DDNS: Dynamic DNS Update 2 (PTR) for host canada_reserved.hacks returned 0 
(NOERROR)
00:19:01: DDNS: Zone name for 'canada_reserved.hacks' is 'hacks'
00:19:01: DDNS: Using server 10.19.192.32
00:19:01: DDNS: Dynamic Update 1: (sending to server 10.19.192.32)
00:19:01: DDNS: Zone = hacks
00:19:01: DDNS: Prerequisite: canada_reserved.hacks not in use
00:19:01: DDNS: Update: add canada_reserved.hacks IN A 10.0.0.8
00:19:01: DDNS: Dynamic DNS Update 1 (A) for host canada_reserved.hacks returned 0 
(NOERROR)
00:19:01: DDNS: Update of 'canada_reserved.hacks' <=> 10.0.0.8 finished
00:19:01: DYNDNSUPD: Another update completed (total outstanding=2)
00:19:11: DDNS: Dynamic DNS Update 1 (PTR) for host canada_reserved.hacks returned 0 
(NOERROR)
00:19:11: DDNS: Dynamic DNS Update 1 (PTR) for host canada_reserved.hacks returned 0 
(NOERROR)
00:19:11: DDNS: Zone name for 'canada_reserved.hacks' is 'hacks'
00:19:11: DDNS: Using server 10.0.0.1
00:19:11: DDNS: Dynamic Update 1: (sending to server 10.0.0.1)
00:19:11: DDNS: Zone = hacks
00:19:11: DDNS: Prerequisite: canada_reserved.hacks not in use
00:19:11: DDNS: Update: add canada_reserved.hacks IN A 10.0.0.8
00:19:11: DDNS: Zone name for 'canada_reserved.hacks' is 'hacks'
00:19:11: DDNS: Using server 10.0.0.1
00:19:11: DDNS: Dynamic Update 1: (sending to server 10.0.0.1)
00:19:11: DDNS: Zone = hacks
00:19:11: DDNS: Prerequisite: canada_reserved.hacks not in use
00:19:11: DDNS: Update: add canada_reserved.hacks IN A 10.0.0.8
00:19:21: DDNS: Dynamic DNS Update 1 (A) for host canada_reserved.hacks returned 0 
(NOERROR)
00:19:21: DDNS: Update of 'canada_reserved.hacks' <=> 10.0.0.8 failed
00:19:21: DYNDNSUPD: Another update completed (total outstanding=1)
00:19:21: DDNS: Dynamic DNS Update 1 (A) for host canada_reserved.hacks returned 0 
(NOERROR)
00:19:21: DDNS: Update of 'canada_reserved.hacks' <=> 10.0.0.8 failed
00:19:21: DYNDNSUPD: Another update completed (total outstanding=0)
Configuring DHCP Support of DDNS Updates

DDNS updates contain information about A or forward RRs for a particular IP address. The IP address is in dotted decimal form, and there must be at least one A record for each host address. The name specified is the hostname expressed as an FQDN (ns.example.com). The PTR or reverse RRs map a domain name to another domain name and is used for reverse mapping (IP address to domain name).

The updates are performed using messages. In general, you will probably want DDNS updates done by the server after the server has sent the ACK response to the DHCP client. Performing the DDNS updates before sending the ACK response will delay the response to the client. Both methods are supported. The default is to do the updates after sending the response.

When looking for a client hostname to use in the update, the server will take the hostname from the FQDN option, if such exists, first. If there is no FQDN option, the server will look for a HOSTNAME option and take the name from there.

If the FQDN or HOSTNAME option is included in subsequent RENEWAL messages, the server will attempt to perform the DDNS update each time the lease is renewed. This process gives the opportunity for the client to change the name specified after the lease has been granted and have the server do the appropriate updates. Although the server has this capability, the DHCP client will continue to use the same hostname throughout the duration of a lease.

The IP address of the server to update is discovered by sending a DNS query for records associated with the hostname to update. If such a record exists, the hostname of the master DNS server is extracted from this information. If no such record exists, the record, which should be included in the response, is used as the authoritative record for the zone where the hostname exists. In either case, once the master DNS server hostname is found, another query for A RRs is sent in order to discover the IP address of this server. The resulting IP address is used for sending updates.

Perform this task to configure the DDNS updates.

Prerequisites

In order for DDNS updates to discover the DNS server, in cases in which the user did not configure the server, the ip name-server command should be configured. This name server should be reachable by the system, and the ip domain lookup command should be configured (which is the default anyway). In cases in which the configured hostname does not include a period (is not a fully qualified domain name [FQDN]), an IP domain name should be configured.

Restrictions

Note DHCP server-pool configuration commands and interface configurations have precedence over global configurations.

SUMMARY STEPS

1. enable

2. configure terminal

3. ip dhcp update dns [both] [override] [before]

4. ip dhcp-client update dns [server {both | none}]

5. 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 dhcp update dns [both] [override] [before]
Example:

Router(config)# ip dhcp update dns both override

Enables DDNS updates of PTR RRs for all address pools except those configured with the per-pool update dns command, which overrides global configuration. The keywords are as follows:

•both—(Optional) Enables the DHCP server to perform DDNS updates for A and PTR RRs, unless the DHCP client has specified in the FQDN option that the server should not perform the updates.

•override—(Optional) Enables the DHCP server to perform DDNS updates for PTR RRs even if the DHCP client has specified in the FQDN option that the server should not perform the updates.

Note If you specify the both and override keywords together, this enables the DHCP server to perform DDNS updates for A and PTR RRs overriding anything the DHCP client specified in the FQDN option to the contrary.

•before—(Optional) Enables the DHCP server to perform DDNS updates before sending the DHCP ACK back to the client. The default is to perform updates after sending the DHCP ACK.

Step 4

ip dhcp-client update dns [server {both | none}]
Example:

Router(config)# ip dhcp-client update dns server both

Enables DDNS updates of PTR RRs. The optional server keyword enables the server to perform DDNS updates for A and PTR RRs. The keywords are as follows:

•both—Enables the DHCP server to perform DDNS updates for A and PTR RRs, unless the DHCP client specifies in the FQDN option that the server should not perform the updates.

•none—Enables the DHCP client to perform DDNS updates and the server will not perform any updates. The server can override this action.

Note The ip dhcp-client update dns server none command instructs the server not to perform any updates. If configured to do so, the server can override the client.

Note The ip dhcp-client update dns server both command instructs the server to update both the A and PTR RRs.

Step 5

exit
Example:

Router(config)# exit

Exits to privileged EXEC mode.

Examples

The following example shows how to configure A and PTR RR updates that are performed by the server only:
ip dhcp-client update dns server both
ip dhcp update dns both override

Configuring DDNS Update Support on Interfaces

Perform this task to configure your interfaces for DDNS update capability.

Note The interface configuration overrides the global configuration.

Prerequisites

In order for DDNS updates to discover the DNS server, in cases in which the user did not configure the server, the ip name-server command should be configured. This name server should be reachable by the system, and the ip domain lookup command should be configured (which is the default anyway). In cases in which the configured hostname does not include a period (is not a fully qualified domain name [FQDN]), an IP domain name should be configured.

Restrictions

The changes will not take effect until any current lease on the interface is released and a new lease is requested that uses a new DHCP DISCOVER packet. This means configuring the ip address dhcp command or using the release dhcp EXEC command followed by the renew dhcp EXEC command.

SUMMARY STEPS

1. enable

2. configure terminal

3. interface interface-type number

4. ip dhcp client update dns [server {both | none}]

5. ip address dhcp

6. 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

interface interface-type number
Example:

Router(config)# interface ethernet1

Specifies an interface type and number and enters interface configuration mode.

Step 4

ip dhcp client update dns [server {both | none}]
Example:

Router(config-if)# ip dhcp client update dns server both

Configures the DHCP client to include an FQDN option when sending packets to the DHCP server. The keywords are as follows:

•both—(Optional) Enables the DHCP server to perform DDNS updates for A and PTR RRs, unless the DHCP client specifies in the FQDN option that the server should not perform the updates.

•none—(Optional) Enables the DHCP client to perform DDNS updates and the server will not perform any updates. The server can override this action.

Note The ip dhcp client update dns server none command instructs the server not to perform any updates. If configured to do so, the server can override the client.

Note The ip dhcp client update dns server both command instructs the server to update both the A and PTR RRs.

Step 5

ip address dhcp
Example:

Router(config-if)# ip address dhcp

Releases any current lease on the interface and enables the configuration.

Note You can also release any lease by using the release dhcp EXEC command followed by the renew dhcp EXEC command.

Step 6

exit
Example:

Router(config-if)# exit

Exits to privileged EXEC mode.

Configuring a Pool of DHCP Servers to Support DDNS Updates

There are two parts to the DDNS update configuration on the client side. First, if the ip ddns update method command is configured on the client, which specifies the DDNS-style updates, then the client will be trying to generate or perform A updates. If the ip ddns update method ddns both command is configured, then the client will be trying to update both A and PTR RRs.

Second, the only way for the client to communicate with the server, with reference to what updates it is generating or expecting the server to generate, is to include an FQDN option when communicating with the server. Whether or not this option is included is controlled on the client side by the ip dhcp-client update dns command in global configuration mode or the ip dhcp client update dns command in interface configuration mode.

If the FQDN option is included in the DHCP interaction, then the client may instruct the server to update "reverse" (the default), "both", or "none." Obviously, if the ip ddns update method command is configured with the ddns and both keywords, then the FQDN option configuration should reflect an IP DHCP client update DNS server none, but you have to configure the system correctly.

Finally, even if the client instructs the server to update both or update none, the server can override the client request and do whatever it was configured to do anyway. If there is an FQDN option in the DHCP interaction as above, then server can communicate to the client that it was overridden, in which case the client will not perform the updates because it knows that the server has done the updates. Even if the server is configured to perform the updates after sending the ACK (the default), it can still use the FQDN option to instruct the client what updates it will be performing and thus the client will not do the same types of updates.

If the server is configured with the update dns command with or without any keywords, and if the server does not see an FQDN option in the DHCP interaction, then it will assume that the client does not understand DDNS and will automatically act as though it were configured to update both A and PTR RRs on behalf of the client.

Perform this task to configure a pool of DHCP servers to support DDNS updates.

Prerequisites

In order for DDNS updates to discover the DNS server, in cases in which the user did not configure the server, the ip name-server command should be configured. This name server should be reachable by the system, and the ip domain lookup command should be configured (which is the default anyway). In cases in which the configured hostname does not include a period (is not a fully qualified domain name [FQDN]), an IP domain name should be configured.

SUMMARY STEPS

1. enable

2. configure terminal

3. ip dhcp pool pool-name

4. update dns [both | never] [override] [before]

5. 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 dhcp pool pool-name
Example:

Router(config)# ip dhcp pool test

Assigns a name to a DHCP pool and enters DHCP configuration mode.

Step 4

update dns [both | never] [override] [before]
Example:

Router(dhcp-config)# update dns never

Enables DDNS update capability for a pool of DHCP servers for any addresses assigned from this address pool.

If the server is configured using this command with or without any of the other keywords, and if the server does not see an FQDN option in the DHCP interaction, then it will assume that the client does not understand DDNS and act as though it were configured to update both A and PTR records on behalf of the client.

The keywords are as follows:

•both—(Optional) Perform forward and reverse updates. If the before optional keyword is specified along with the both keyword, the server can perform DDNS updates before sending the ACK back to the client.

If the override optional keyword is specified with the both keyword, the server can override the client and update forward and reverse RRs.

If the override and before optional keywords are specified with the both keyword, the server can override the client (forward and reverse updates) and perform the updates before sending the ACK.

•never—(Optional) Never perform updates for this pool.

•override—(Optional) Override the client FQDN flags. If the before optional keyword is specified, the updates will be performed before sending the ACK.

•before—(Optional) Perform updates before sending the ACK.

Step 5

exit
Example:

Router(dhcp-config)# exit

Exits to global configuration mode.

Examples

The following example shows how to configure a pool of DHCP servers to perform updates for A and PTR RRs before the ACK is sent:
ip dhcp pool test
 update dns both before
Configuring the Update Method and Interval

Perform this task to specify the update method and interval maximum.

Prerequisites

In order for DDNS updates to discover the DNS server, in cases in which the user did not configure the server, the ip name-server command should be configured. This name server should be reachable by the system, and the ip domain lookup command should be configured (which is the default anyway). In cases in which the configured hostname does not include a period (is not a fully qualified domain name [FQDN]), an IP domain name should be configured.

SUMMARY STEPS

1. enable

2. configure terminal

3. ip ddns update method method-name

4. interval minimum days hours minutes seconds

5. interval maximum days hours minutes seconds

6. ddns [both]

7. internal

8. http

9. add url

10. remove url

11. exit

12. exit

13. interface interface-type number

14. ip ddns update hostname hostname

15. ip ddns update method-name

16. 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 ddns update method method-name
Example:

Router(config)# ip ddns update method myupdate

Specifies the update method name and enters DDNS update method configuration mode.

Step 4

interval minimum days hours minutes seconds
Example:

Router(DDNS-update-method)# interval minimum 1 0 0 0

Configures a minimum update interval. The arguments are as follows:

•days—Range is from 0 to 365.

•hours—Range is from 0 to 23.

•minutes—Range is from 0 to 59.

•seconds—Range is from 0 to 59.

Step 5

interval maximum days hours minutes seconds
Example:

Router(DDNS-update-method)# interval maximum 1 0 0 0

Configures a maximum update interval. The arguments are as follows:

•days—Range is from 0 to 365.

•hours—Range is from 0 to 24.

•minutes—Range is from 0 to 60.

•seconds—Range is from 0 to 60.

Step 6

ddns [both]
Example:

Router(DDNS-update-method)# ddns

Configures DDNS as the update method. The both keyword specifies that both A and PTR RRs will be updated.

Note You can specify DDNS or HTTP but not both in one step. If you have specified DDNS, you must disable it by using the no ddns command before you can configure HTTP. For the HTTP configuration, see Steps 7,8, and 9.

Step 7

internal
Example:

Router(DDNS-update-method)# internal

Specifies that an internal cache will be used as the update method.

Step 8

http
Example:

Router(DDNS-update-method)# http

Configures HTTP as the update method and enters DDNS-HTTP configuration mode.

Step 9

add url
Example:

Router(DDNS-HTTP)# add http://test:test@members.dyndns.org/nic/update? system=dyndns&hostname=<h>&myip=<a>

Configures a URL that should be invoked in order to add or change a mapping between a hostname and an IP address. The following example configures the URL to be invoked to add or change the mapping information using DynDNS.org:

•http://userid:password@members.dyndns.org/nic/update?system=dyndns&hostname=<h>&myip=<a>.

You have to enter the URL string above. Userid is your userid and password is your password at the DynDNS.org website. The special character strings <h> and <a> will be substituted with the hostname to update and the IP address with which that hostname should be associated, respectively.

Note Before entering the question mark (?) character, press the control (Ctrl) key and the v key together on your keyboard. This will allow you to enter the ? without the software interpreting the ? as a help query.

Step 10

remove url
Example:

Router(DDNS-HTTP)# remove http://test:test@members.dyndns.org/nic/update? system=dyndns&hostname=<h>&myip=<a>

Configures a URL that should be invoked in order to remove a mapping between a hostname and an IP address. The URL takes the same form as the add keyword in Step 8.

Step 11

exit
Example:

Router(DDNS-HTTP)# exit

Exits to update-method configuration mode.

Step 12

exit
Example:

Router(DDNS-update-method)# exit

Exits to global configuration mode.

Step 13

interface interface-type number
Example:

Router(config)# interface ether1

Enters interface configuration mode.

Step 14

ip ddns update hosthame hostname
Example:

Router(config-if)# ip ddns update hostname abc.dyndns.org

Specifies a host to be used for the updates. The update will associate this hostname with the configured IP address of the interface. The hostname argument specifies the hostname that will receive the updates (for example, DynDNS.org).

Step 15

ip ddns update name
Example:

Router(config-if) ip ddns update myupdate

Specifies the name of the update method to use for sending Dynamic DNS updates associated with address changes on this interface.

Step 16

exit
Example:

Router(config)# exit

Exits to privileged EXEC mode.

Examples

The following example shows how to configure the update method, the maximum interval of the updates (globally), and configure the hostname on the interface:
ip ddns update method mytest
ddns
 http
!Before entering the question mark (?) character in the add http CLI, press the control 
(Ctrl) key and the v key together on your keyboard. This will allow you to enter the ? 
without the software interpreting the ? as a help query.
add http://test:test@members.dyndns.org/nic/update?system=dyndns&hostname=<h>&myip=<a>
 interval maximum 1 0 0 0
 exit
interface ether1
ip ddns update hostname abc.dyndns.org
 ip ddns update mytest
Verifying DDNS Updates

Use the debug ip ddns update command to verify that DDNS updates are being performed. There are several sample configurations and the debug output that would display for that scenario.

Sample Configuration #1

The following scenario has a client configured for IETF DDNS updating of A DNS RRs during which a DHCP server is expected to update the PTR DNS RR. The DHCP client discovers the DNS server to update using an SOA RR lookup since the IP address to the server to update is not specified. The DHCP client is configured to include an FQDN DHCP option and notifies the DHCP server that it will be updating the A RRs.
!Configure the DHCP Client
ip ddns update method testing
 ddns
interface Ethernet1
 ip dhcp client update dns
 ip ddns update testing
 ip address dhcp
end
!Configure the DHCP Server
ip dhcp pool test
 network 10.0.0.0 255.0.0.0
 update dns
!Enable Debugging
Router# debug ip ddns update
00:14:39:%DHCP-6-ADDRESS_ASSIGN: Interface Ethernet1 assigned DHCP address 10.0.0.4, mask 
255.0.0.0, hostname canada_reserved
00:14:39: DYNDNSUPD: Adding DNS mapping for canada_reserved.hacks <=> 10.0.0.4
00:14:39: DYNDNSUPD: Sleeping for 3 seconds waiting for interface Ethernet1 configuration 
to settle
00:14:42: DHCPC: Server performed PTR update
00:14:42: DDNS: Enqueuing new DDNS update 'canada_reserved.hacks' <=> 10.0.0.4
00:14:42: DDNS: Zone name for 'canada_reserved.hacks' is 'hacks'
00:14:42: DDNS: Dynamic Update 1: (sending to server 10.19.192.32)
00:14:42: DDNS:   Zone = hacks
00:14:42: DDNS:   Prerequisite: canada_reserved.hacks not in use
00:14:42: DDNS:   Update: add canada_reserved.hacks IN A 10.0.0.4
00:14:42: DDNS: Dynamic DNS Update 1 (A) for host canada_reserved.hacks returned 0 
(NOERROR)
00:14:42: DDNS: Update of 'canada_reserved.hacks' <=> 10.0.0.4 finished
00:14:42: DYNDNSUPD: Another update completed (total outstanding=0)
Sample Configuration #2

The following scenario has the client configured for IETF DDNS updating of both A and DNS RRs and requesting that the DHCP server update neither. The DHCP client discovers the DNS server to update using an SOA RR lookup since the IP address to the server to update is not specified. The DHCP client is configured to include an FQDN DHCP option that instructs the DHCP server not to update either A or PTR RRs. This is configured using the global version of the command.
!Configure the DHCP Client
ip dhcp-client update dns server none
ip ddns update method testing
 ddns both
interface Ethernet1
 ip ddns update testing
 ip address dhcp
end
!Configure the DHCP Server
ip dhcp pool test
 network 10.0.0.0 255.0.0.0
 update dns
!Enable Debugging
Router# debug ip ddns update
00:15:33:%DHCP-6-ADDRESS_ASSIGN: Interface Ethernet1 assigned DHCP address 10.0.0.5, mask 
255.0.0.0, hostname canada_reserved
00:15:33: DYNDNSUPD: Adding DNS mapping for canada_reserved.hacks <=> 10.0.0.5
00:15:33: DYNDNSUPD: Sleeping for 3 seconds waiting for interface Ethernet1 configuration 
to settle
00:15:36: DDNS: Enqueuing new DDNS update 'canada_reserved.hacks' <=> 10.0.0.5
00:15:36: DDNS: Zone name for '10.0.0.11.in-addr.arpa.' is '10.in-addr.arpa'
00:15:36: DDNS: Dynamic Update 1: (sending to server 10.19.192.32)
00:15:36: DDNS:   Zone = 10.in-addr.arpa
00:15:36: DDNS:   Prerequisite: 10.0.0.11.in-addr.arpa. not in use
00:15:36: DDNS:   Update: add 10.0.0.11.in-addr.arpa. IN PTR canada_reserved.hacks
00:15:36: DDNS: Dynamic DNS Update 1 (PTR) for host canada_reserved.hacks returned 0 
(NOERROR)
00:15:36: DDNS: Zone name for 'canada_reserved.hacks' is 'hacks'
00:15:36: DDNS: Dynamic Update 1: (sending to server 10.19.192.32)
00:15:36: DDNS:   Zone = hacks
00:15:36: DDNS:   Prerequisite: canada_reserved.hacks not in use
00:15:36: DDNS:   Update: add canada_reserved.hacks IN A 10.0.0.5
00:15:36: DDNS: Dynamic DNS Update 1 (A) for host canada_reserved.hacks returned 0 
(NOERROR)
00:15:36: DDNS: Update of 'canada_reserved.hacks' <=> 10.0.0.5 finished
00:15:36: DYNDNSUPD: Another update completed (total outstanding=0)
Sample Configuration #3

The following scenario the client is configured for IETF DDNS updating of both A and DNS RRs and requesting that the DHCP server update neither. The DHCP client explicitly specifies the server to update. The DHCP client is configured to include an FQDN DHCP option which instructs the DHCP server not to update either A or PTR RRs. This is configured using the global version of the command. The DHCP server is configured to override the client request and update both A and PTR RR anyway.
!Configure the DHCP Client
ip dhcp client update dns server non
ip ddns update method testing
 ddns both
interface Ethernet1
 ip dhcp client update dns server none
 ip ddns update testing
 ip address dhcp
end
!Configure the DHCP Server
ip dhcp pool test
 network 10.0.0.0 255.0.0.0
 update dns both override
!Enable Debugging on the DHCP Client
Router# debug ip ddns update
00:16:30:%DHCP-6-ADDRESS_ASSIGN: Interface Ethernet1 assigned DHCP address 10.0.0.6, mask 
255.0.0.0, hostname canada_reserved
00:16:30: DYNDNSUPD: Adding DNS mapping for canada_reserved.hacks <=> 10.0.0.6
00:16:30: DYNDNSUPD: Sleeping for 3 seconds waiting for interface Ethernet1 configuration 
to settle
00:16:33: DHCPC: Server performed both updates
Sample Configuration #4

In the following scenario the client is configured for IETF DDNS updating of both A and DNS RRs and requesting the DHCP server to update neither. The DHCP client explicitly specifies the server to update. The DHCP client is configured to include an FQDN DHCP option which instructs the DHCP server not to update either A or PTR RRs. This is configured using the global version of the command. The DHCP server is configured to allow the client to update whatever RR it chooses.
!Configure the DHCP Client
ip dhcp client update dns server non
ip ddns update method testing
 ddns both
interface Ethernet1
 ip dhcp client update dns server none
 ip ddns update testing host 172.19.192.32
 ip address dhcp
end
!Configure the DHCP Server
ip dhcp pool test
 network 10.0.0.0 255.0.0.0
 update dns
!Enable Debugging on the DHCP Client
Router# debug ip ddns update
00:17:52:%DHCP-6-ADDRESS_ASSIGN: Interface Ethernet1 assigned DHCP address 10.0.0.7, mask 
255.0.0.0, hostname canada_reserved
00:17:52: DYNDNSUPD: Adding DNS mapping for canada_reserved.hacks <=> 10.0.0.6
00:17:52: DYNDNSUPD: Sleeping for 3 seconds waiting for interface Ethernet1 configuration 
to settle
00:17:55: DDNS: Enqueuing new DDNS update 'canada_reserved.hacks' <=> 10.0.0.7
00:17:55: DYNDNSUPD: Adding DNS mapping for canada_reserved.hacks <=> 10.0.0.7 server 
10.19.192.32
00:17:55: DDNS: Enqueuing new DDNS update 'canada_reserved.hacks' <=> 10.0.0.7 server 
10.19.192.32
00:17:55: DDNS: Zone name for '10.0.0.11.in-addr.arpa.' is '11.in-addr.arpa'
00:17:55: DDNS: Dynamic Update 1: (sending to server 10.19.192.32)
00:17:55: DDNS: Zone = 10.in-addr.arpa
00:17:55: DDNS: Prerequisite: 10.0.0.11.in-addr.arpa. not in use
00:17:55: DDNS: Update: add 10.0.0.11.in-addr.arpa. IN PTR canada_reserved.hacks
00:17:55: DDNS: Zone name for '10.0.0.11.in-addr.arpa.' is '10.in-addr.arpa'
00:17:55: DDNS: Using server 10.19.192.32
00:17:55: DDNS: Dynamic Update 1: (sending to server 10.19.192.32)
00:17:55: DDNS: Zone = 10.in-addr.arpa
00:17:55: DDNS: Prerequisite: 10.0.0.11.in-addr.arpa. not in use
00:17:55: DDNS: Update: add 10.0.0.11.in-addr.arpa. IN PTR canada_reserved.hacks
00:17:55: DDNS: Dynamic DNS Update 1 (PTR) for host canada_reserved.hacks returned 0 
(NOERROR)
00:17:55: DDNS: Dynamic DNS Update 1 (PTR) for host canada_reserved.hacks returned 6 
(YXDOMAIN)
00:17:55: DDNS: Dynamic Update 2: (sending to server 10.19.192.32)
00:17:55: DDNS: Zone = 10.in-addr.arpa
00:17:55: DDNS: Update: delete 10.0.0.11.in-addr.arpa. all PTR RRs
00:17:55: DDNS: Update: add 10.0.0.11.in-addr.arpa. IN PTR canada_reserved.hacks
00:17:55: DDNS: Dynamic DNS Update 2 (PTR) for host canada_reserved.hacks returned 0 
(NOERROR)
00:17:55: DDNS: Zone name for 'canada_reserved.hacks' is 'hacks'
00:17:55: DDNS: Dynamic Update 1: (sending to server 10.19.192.32)
00:17:55: DDNS: Zone = hacks
00:17:55: DDNS: Prerequisite: canada_reserved.hacks not in use
00:17:55: DDNS: Update: add canada_reserved.hacks IN A 10.0.0.7
00:17:55: DDNS: Dynamic DNS Update 1 (A) for host canada_reserved.hacks returned 0 
(NOERROR)
00:17:55: DDNS: Update of 'canada_reserved.hacks' <=> 10.0.0.7 finished
00:17:55: DYNDNSUPD: Another update completed (total outstanding=1)
00:17:55: DDNS: Zone name for 'canada_reserved.hacks' is 'hacks'
00:17:55: DDNS: Using server 10.19.192.32
00:17:55: DDNS: Dynamic Update 1: (sending to server 10.19.192.32)
00:17:55: DDNS: Zone = hacks
00:17:55: DDNS: Prerequisite: canada_reserved.hacks not in use
00:17:55: DDNS: Update: add canada_reserved.hacks IN A 10.0.0.7
00:17:55: DDNS: Dynamic DNS Update 1 (A) for host canada_reserved.hacks returned 6 
(YXDOMAIN)
00:17:55: DDNS: Dynamic Update 2: (sending to server 10.19.192.32)
00:17:55: DDNS: Zone = hacks
00:17:55: DDNS: Update: delete canada_reserved.hacks all A RRs
00:17:55: DDNS: Update: add canada_reserved.hacks IN A 10.0.0.7
00:17:55: DDNS: Dynamic DNS Update 2 (A) for host canada_reserved.hacks returned 0 
(NOERROR)
00:17:55: DDNS: Update of 'canada_reserved.hacks' <=> 10.0.0.7 finished
00:17:55: DYNDNSUPD: Another update completed (total outstanding=0)
Sample Configuration #5

In the following scenario, the debug output is displaying internal host table updates when the default domain name is "hacks." The "test" update method specifies that the internal Cisco IOS host table should be updated. Configuring the update method as "test" should be used when the address on the Ethernet 0/0 interface changes. The hostname is configured for the update on this interface.
ip domain name hacks
ip ddns update method test
 internal
interface ethernet0/0
 ip ddns update test hostname test2
 ip addr dhcp
!Enable Debugging
Router# debug ip ddns update
*Jun 4 03:11:10.591:%DHCP-6-ADDRESS_ASSIGN: Interface Ethernet0/0 assigned DHCP address 
10.0.0.5, mask 255.0.0.0, hostname test2
*Jun 4 03:11:10.591: DYNDNSUPD: Adding DNS mapping for test2.hacks <=> 10.0.0.5
*Jun 4 03:11:10.591: DYNDNSUPD: Adding internal mapping test2.hacks <=> 10.0.0.5
Using the show hosts command displays the newly added host table entry.
Router# show hosts
Default domain is hacks
Name/address lookup uses domain service
Name servers are 255.255.255.255
Codes: UN - unknown, EX - expired, OK - OK,?? - revalidate
       temp - temporary, perm - permanent
       NA - Not Applicable None - Not defined
Host                      Port Flags      Age Type   Address(es)
test2.hacks               None (perm, OK) 0   IP    10.0.0.5
Shutting down the interface removes the host table entry.
interface ethernet0/0
 shutdown
*Jun 4 03:14:02.107: DYNDNSUPD: Removing DNS mapping for test2.hacks <=> 10.0.0.5
*Jun 4 03:14:02.107: DYNDNSUPD: Removing mapping test2.hacks <=> 10.0.0.5
The show hosts command output shows the entry has been removed.
Router# show hosts
Default domain is hacks
Name/address lookup uses domain service
Name servers are 255.255.255.255
Codes: UN - unknown, EX - expired, OK - OK,?? - revalidate
       temp - temporary, perm - permanent
       NA - Not Applicable None - Not defined
Host                      Port Flags      Age Type   Address(es)
Sample Configuration #6

In the following scenario, the debug output shows the HTTP-style DDNS updates. The sample configuration defines a new IP DDNS update method named dyndns that configures a URL to use when adding or changing an address. No URL has been defined for use when removing an address since DynDNS.org does not use such a URL for free accounts. A maximum update interval of 28 days has been configured, so specifying that updates should be sent at least every 28 days. Configuring the new dyndns update method should be used for Ethernet interface .

Note Before entering the question mark (?) character in the "add http" configuration after the update keyword, press the control (Ctrl) key and the "v" key together on your keyboard. This will allow you to enter the ? without the software interpreting it as a help query.
!Configure the DHCP Client
ip ddns update method dyndns
 http
    add http://test:test@<s>/nic/update?system=dyndns&hostname=<h>&myip=<a>
    interval max 28 0 0 0
interface ethernet1
 ip ddns update hostname test.dyndns.org
 ip ddns update dyndns host members.dyndns.org
 ip addr dhcp
!Enable Debugging
Router# debug ip ddns update
00:04:35:%DHCP-6-ADDRESS_ASSIGN: Interface Ethernet1 assigned DHCP address 10.32.254.187, 
mask 255.255.255.240, hostname test.dyndns.org
00:04:35: DYNDNSUPD: Adding DNS mapping for test.dyndns.org <=> 10.32.254.187 server 
10.208.196.94
00:04:35: DYNDNSUPD: Sleeping for 3 seconds waiting for interface Ethernet1 configuration 
to settle
00:04:38: HTTPDNS: Update add called for test.dyndns.org <=> 10.32.254.187
00:04:38: HTTPDNS: Update called for test.dyndns.org <=> 10.32.254.187
00:04:38: HTTPDNS: init
00:04:38: HTTPDNSUPD: Session ID = 0x7
00:04:38: HTTPDNSUPD: URL = 
'http://test:test@10.208.196.94/nic/update?system=dyndns&hostname=test.dyndns.org&myip=10.
32.254.187'
00:04:38: HTTPDNSUPD: Sending request
00:04:40: HTTPDNSUPD: Response for update test.dyndns.org <=> 10.32.254.187
00:04:40: HTTPDNSUPD: DATA START
good 10.32.254.187
00:04:40: HTTPDNSUPD: DATA END, Status is Response data received, successfully
00:04:40: HTTPDNSUPD: Call returned SUCCESS for update test.dyndns.org <=> 10.32.254.187
00:04:40: HTTPDNSUPD: Freeing response
00:04:40: DYNDNSUPD: Another update completed (outstanding=0, total=0)
00:04:40: HTTPDNSUPD: Clearing all session 7 info
!28 days later, the automatic update happens.
00:05:39: DYNDNSUPD: Adding DNS mapping for test.dyndns.org <=> 10.32.254.187 server 
10.208.196.94
00:05:39: HTTPDNS: Update add called for test.dyndns.org <=> 10.32.254.187
00:05:39: HTTPDNS: Update called for test.dyndns.org <=> 10.32.254.187
00:05:39: HTTPDNS: init
00:05:39: HTTPDNSUPD: Session ID = 0x8
00:05:39: HTTPDNSUPD: URL = 
'http://test:test@10.208.196.94/nic/update?system=dyndns&hostname=test.dyndns.org&myip=10.
32.254.187'
00:05:39: HTTPDNSUPD: Sending request
00:05:39: HTTPDNSUPD: Response for update test.dyndns.org <=> 10.32.254.187
00:05:39: HTTPDNSUPD: DATA START
nochg 10.32.254.187
00:05:39: HTTPDNSUPD: DATA END, Status is Response data received, successfully
00:05:39: HTTPDNSUPD: Call returned SUCCESS for update test.dyndns.org <=> 10.32.254.187
00:05:39: HTTPDNSUPD: Freeing response
00:05:39: DYNDNSUPD: Another update completed (outstanding=0, total=0)
00:05:39: HTTPDNSUPD: Clearing all session 8 info
Configuration Examples for Dynamic DNS Support for Cisco IOS Software

The section contains the following configuration examples:

•Configuration of the DHCP Client: Example

•Configuration of the DHCP Server: Example

•Configuration of the HTTP Updates: Example

Configuration of the DHCP Client: Example

The following example shows that no DDNS updates will be performed for addresses assigned from the address pool "abc." Addresses allocated from the address pool "def" will have both forward (A) and reverse (PTR) updates performed. This configuration has precedence over the global server configurations.
ip dhcp update dns both override
 ip dhcp pool abc
  network 10.1.0.0 255.255.0.0
!
 update dns never
!
 ip dhcp pool def
  network 10.10.0.0 255.255.0.0
Configuration of the DHCP Server: Example

The following example shows how to configure A and PTR RR updates that are performed by the server only:
ip dhcp-client update dns server both
ip dhcp update dns both override

Configuration of the HTTP Updates: Example

The following example shows how to configure a PPPoE server for HTTP DDNS:
!Username and Password for PPP Authentication Configuration
!
username user1 password 0 cisco
!
!DHCP Pool Configuration
ip dhcp pool mypool
 network 10.10.10.0 255.255.255.0
 default-router 10.10.10.1
!
!VPDN configuration for PPPoE
vpdn enable
!
vpdn-group pppoe
accept-dialin
protocol pppoe
virtual-template 1
!
interface Loopback0
ip address 10.10.10.1 255.255.255.0
!
!Port used to connect to the Internet, it can be the same port that is under test, but to 
make the test clear and simple these two are separated.
!
interface FastEthernet0/0
 ip address 10.0.58.71 255.255.255.0
!
!Port under test.
!
interface FastEthernet0/1
 no ip address
 pppoe enable
!
!Virtual template and address pool config for PPPoE.
interface Virtual-Template1
 ip unnumbered Loopback0
 ip mtu 1492
 peer default ip address dhcp-pool mypool
 ppp authentication chap
The following example shows how to configure a DHCP client for IETF DDNS:
!Default hostname of the router.
hostname mytest
!
!Default domain name on the router.
ip domain name test.com
!
!Port under test.
!
interface FastEthernet0/1
 no ip address (configured to "ip address dhcp")
The following example shows how to configure the method of update and the maximum interval of the updates (globally) and configure the hostname on the interface:

Note Before entering the question mark (?) character in the "add http" configuration after the update keyword, press the control (Ctrl) key and the "v" key together on your keyboard. This will allow you to enter the ? without the software interpreting it as a help query.
ip ddns update method mytest
ddns
 http
add http://test:test@members.dyndns.org/nic/update?system=dyndns&hostname=<h>&myip=<a>
 interval maximum 1 0 0 0
 exit
interface ether1
ip ddns update hostname abc.dyndns.org
 ip ddns update mytest
The following are examples of URLs that can be used to update some HTTP DNS update services. These URLs are correct to the best of the knowledge of Cisco but have not been tested in all cases. Where the word "USERNAME:" appears in the URL, the customer account username at the HTTP site should be used.

Where the word "PASSWORD" appears in the URL, the customer password for that account should be used:

Note Before entering the question mark (?) character in the "add http" configuration after the update keyword, press the control (Ctrl) key and the "v" key together on your keyboard. This will allow you to enter the ? without the software interpreting it as a help query.

DDNS
http://USERNAME:PASSWORD@members.dyndns.org/nic/update?system=dyndns&hostname=<h>&myip=<a>
!Requires "interval max 28 0 0 0" in the update method definition.
TZO
http://cgi.tzo.com/webclient/signedon.html?TZOName=<h>&Email=USERNAME&TZOKey=PASSWORD&IPAd
dress=<a>
EASYDNS
http://USERNAME:PASSWORD@members.easydns.com/dyn/ez-ipupdate.php?action=edit&myip=<a>&host
_id=<h>
JUSTLINUX
http://USERNAME:PASSWORD@www.justlinux.com/bin/controlpanel/dyndns/jlc.pl?direst=1&usernam
e=USERNAME&password=PASSWORD&host=<h>&ip=<a>
DYNS
http://USERNAME:PASSWORD@www.dyns.cx/postscript.php?username=USERNAME&password=PASSWORD&ho
st=<h>&ip=<a>
HN
http://USERNAME:PASSWORD@dup.hn.org/vanity/update?ver=1&IP=<a>
ZONEEDIT
http://USERNAME:PASSWORD@www.zoneedit.com/auth/dynamic.html?host=<h>&dnsto=<a>
Note Because these services are provided by the respective companies, the URLs may be subject to change or the service could be discontinued at any time. Cisco takes no responsibility for the accuracy or use of any of this information. The URLs were obtained using an application called "ez-ipupdate," which is available for free on the Internet.

Additional References

The following sections provide references related to the Dynamic DNS Support for Cisco IOS Software feature.

Related Documents

Related Topic

Document Title

DNS Configuration Tasks

Configuring DNS module

DNS commands: complete command syntax, command mode, command history, defaults, usage guidelines, and examples

Cisco IOS IP Addressing Services 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

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

RFCs

RFCs

Title

RFC 2136

Dynamic Updates in the Domain Name System (DNS Update)

RFC 3007

Secure Domain Name System (DNS) Dynamic Update

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

Command Reference

The following commands are introduced or modified in the feature or features documented in this module. For information about these commands, see the Cisco IOS IP Addressing Command Reference at http://www.cisco.com/en/US/docs/ios/ipaddr/command/reference/iad_book.html. For information about all Cisco IOS commands, go to the Command Lookup Tool at http://tools.cisco.com/Support/CLILookup or to the Cisco IOS Master Commands List.

•ddns (DDNS-update-method)

•debug ip ddns update

•host (host-list)

•http (DDNS-update-method)

•internal (DDNS-update-method)

•interval maximum

•ip ddns update hostname

•ip ddns update method

•ip dhcp client update dns

•ip dhcp-client update dns

•ip dhcp update dns

•ip host-list

•show ip ddns update

•show ip ddns update method

•show ip host-list

•update dns

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.

© 2007 Cisco Systems, Inc. All rights reserved.