Table Of Contents
Dynamic DNS Support for Cisco IOS Software
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
Feature Design of Dynamic DNS Support for Cisco IOS Software
How to Configure Dynamic DNS Support for Cisco IOS Software
Verifying the Host-List Configuration
Configuring DHCP Support of DDNS Updates
Configuring DDNS Update Support on Interfaces
Configuring a Pool of DHCP Servers to Support DDNS Updates
Configuring the Update Method and Interval
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
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.
Feature History for the Dynamic DNS Support for Cisco IOS Software 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 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, page 28
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
Examples
The following example shows how to configure several hosts with VRF:
ip host-list abchost 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.comhost 10.6.6.6 f.comhost vrf abc a.com b.com c.comhost vrf def 10.1.1.1 10.2.2.2 10.3.3.3Verifying 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: abcddns.abc10.2.3.4ddns2.abc10.3.4.5ddns3.com10.3.3.3d.orge.org1.org.2.org3.com10.2.2.2 (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 aip host-list bip host-list cip host-list abcStep 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 whoip host who 10.0.0.2ip host-list ahost 10.1.1.1 a.com b.com 10.2.2.3 10.2.2.2 c.com. 10.3.3.3 10.4.4.4host d.comhost vrf abc 10.10.10.4 10.10.10.8host vrf def 10.2.3.4 10.6.7.8ip host-list bhost a.com b.com c.com 10.1.1.1 10.2.2.2 10.3.3.3host vrf ppp 10.2.1.0ip host-list chost 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.comhost 10.6.6.6 f.comhost vrf zero a.com b.com c.omhost vrf one 10.1.1.1 10.2.2.2 10.3.3.3ip host-list unit-testhost ddns.unit.test 10.2.3.4 ddns2.unit.test 10.3.4.5 ddns3.com 10.3.3.3 d.org e.orghost 1.org.2.org 3.comhost vrf ZERO 10.2.2.2 10.5.5.5 a.net b.netip ddns update hostname use-this.host.nameip ddns update this-method host 10.2.3.4ip ddns update this-method host this-hostip ddns update this-method host-group this-listip ddns update this-method host 10.3.4.5ip ddns update test host 10.19.192.32ip ddns update test host 10.19.192.32ip ddns update a host-group aip ddns update a host-group abip ddns update aa host-group abip ddns update method host 10.33.44.55Step 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 which 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 Clientip host-list servershost 10.19.192.32 10.0.0.1ip ddns update method testingddnsinterface Ethernet1ip dhcp client update dns server noneip ddns update testing host-group serversip address dhcpend!Configure the DHCP Serverip dhcp pool testnetwork 10.0.0.0 255.0.0.0update dns!Enable Debuggingdebug ip ddns update!The update to the server 10.0.0.1 fails in this example00:18:58:%DHCP-6-ADDRESS_ASSIGN: Interface Ethernet1 assigned DHCP address 10.0.0.8, mask 255.0.0.0, hostname canada_reserved00:18:58: DYNDNSUPD: Adding DNS mapping for canada_reserved.hacks <=> 10.0.0.8 server 10.19.192.3200:18:58: DYNDNSUPD: Sleeping for 3 seconds waiting for interface Ethernet1 configuration to settle00:19:01: DDNS: Enqueuing new DDNS update 'canada_reserved.hacks' <=> 10.0.0.8 server 10.19.192.3200:19:01: DYNDNSUPD: Adding DNS mapping for canada_reserved.hacks <=> 10.0.0.8 server 10.0.0.100:19:01: DDNS: Enqueuing new DDNS update 'canada_reserved.hacks' <=> 10.0.0.8 server 10.0.0.100:19:01: DYNDNSUPD: Adding DNS mapping for canada_reserved.hacks <=> 10.0.0.8 server 10.0.0.100:19:01: DDNS: Enqueuing new DDNS update 'canada_reserved.hacks' <=> 10.0.0.8 server 10.0.0.100:19:01: DDNS: Zone name for '10.0.0.11.in-addr.arpa.' is '10.in-addr.arpa'00:19:01: DDNS: Using server 10.19.192.3200:19:01: DDNS: Dynamic Update 1: (sending to server 10.19.192.32)00:19:01: DDNS: Zone = 10.in-addr.arpa00:19:01: DDNS: Prerequisite: 10.0.0.11.in-addr.arpa. not in use00:19:01: DDNS: Update: add 10.0.0.11.in-addr.arpa. IN PTR canada_reserved.hacks00:19:01: DDNS: Zone name for '10.0.0.11.in-addr.arpa.' is '10.in-addr.arpa'00:19:01: DDNS: Using server 10.0.0.100:19:01: DDNS: Dynamic Update 1: (sending to server 10.0.0.1)00:19:01: DDNS: Zone = 10.in-addr.arpa00:19:01: DDNS: Prerequisite: 10.0.0.11.in-addr.arpa. not in use00:19:01: DDNS: Update: add 10.0.0.11.in-addr.arpa. IN PTR canada_reserved.hacks00:19:01: DDNS: Zone name for '10.0.0.11.in-addr.arpa.' is '10.in-addr.arpa'00:19:01: DDNS: Using server 10.0.0.100:19:01: DDNS: Dynamic Update 1: (sending to server 10.0.0.1)00:19:01: DDNS: Zone = 10.in-addr.arpa00:19:01: DDNS: Prerequisite: 10.0.0.11.in-addr.arpa. not in use00:19:01: DDNS: Update: add 10.0.0.11.in-addr.arpa. IN PTR canada_reserved.hacks00:19:01: 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.arpa00:19:01: DDNS: Update: delete 10.0.0.11.in-addr.arpa. all PTR RRs00:19:01: DDNS: Update: add 10.0.0.11.in-addr.arpa. IN PTR canada_reserved.hacks00:19:01: 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 10.19.192.3200:19:01: DDNS: Dynamic Update 1: (sending to server 10.19.192.32)00:19:01: DDNS: Zone = hacks00:19:01: DDNS: Prerequisite: canada_reserved.hacks not in use00:19:01: DDNS: Update: add canada_reserved.hacks IN A 10.0.0.800:19:01: 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 finished00:19:01: 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 10.0.0.100:19:11: DDNS: Dynamic Update 1: (sending to server 10.0.0.1)00:19:11: DDNS: Zone = hacks00:19:11: DDNS: Prerequisite: canada_reserved.hacks not in use00:19:11: DDNS: Update: add canada_reserved.hacks IN A 10.0.0.800:19:11: DDNS: Zone name for 'canada_reserved.hacks' is 'hacks'00:19:11: DDNS: Using server 10.0.0.100:19:11: DDNS: Dynamic Update 1: (sending to server 10.0.0.1)00:19:11: DDNS: Zone = hacks00:19:11: DDNS: Prerequisite: canada_reserved.hacks not in use00:19:11: DDNS: Update: add canada_reserved.hacks IN A 10.0.0.800:19:21: 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 failed00:19:21: 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 failed00:19:21: 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
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 bothip 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 {reverse | both | none}]
5. ip address dhcp
6. exit
DETAILED STEPS
Examples
The following example shows an interface configuration that has precedence over a global configuration. The server will perform reverse updates for Ethernet interface 1. Ethernet interface 2 has both forward and reverse updates done by the server.
ip dhcp-client update dns server bothinterface ethernet1ip dhcp client update dns server reverseip address dhcpinterface ethernet2ip address dhcpConfiguring 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
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 testupdate dns both beforeConfiguring 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. ddns [both]
5. internal name-cache
6. http
7. add url
8. remove url
9. interval maximum days hours minutes seconds
10. exit
11. exit
12. interface interface-type number
13. ip ddns update hostname hostname
14. ip ddns update method-name
15. exit
DETAILED STEPS
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 mytestddnshttp!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 0exitinterface ether1ip ddns update hostname abc.dyndns.org
ip ddns update mytestVerifying 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 Clientip ddns update method testingddnsinterface Ethernet1ip dhcp client update dnsip ddns update testingip address dhcpend!Configure the DHCP Serverip dhcp pool testnetwork 10.0.0.0 255.0.0.0update dns!Enable DebuggingRouter# debug ip ddns update00:14:39:%DHCP-6-ADDRESS_ASSIGN: Interface Ethernet1 assigned DHCP address 10.0.0.4, mask 255.0.0.0, hostname canada_reserved00:14:39: DYNDNSUPD: Adding DNS mapping for canada_reserved.hacks <=> 10.0.0.400:14:39: DYNDNSUPD: Sleeping for 3 seconds waiting for interface Ethernet1 configuration to settle00:14:42: DHCPC: Server performed PTR update00:14:42: DDNS: Enqueuing new DDNS update 'canada_reserved.hacks' <=> 10.0.0.400:14:42: 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 = hacks00:14:42: DDNS: Prerequisite: canada_reserved.hacks not in use00:14:42: DDNS: Update: add canada_reserved.hacks IN A 10.0.0.400:14:42: 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 finished00:14:42: 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 Clientip dhcp-client update dns server noneip ddns update method testingddns bothinterface Ethernet1ip ddns update testingip address dhcpend!Configure the DHCP Serverip dhcp pool testnetwork 10.0.0.0 255.0.0.0update dns!Enable DebuggingRouter# debug ip ddns update00:15:33:%DHCP-6-ADDRESS_ASSIGN: Interface Ethernet1 assigned DHCP address 10.0.0.5, mask 255.0.0.0, hostname canada_reserved00:15:33: DYNDNSUPD: Adding DNS mapping for canada_reserved.hacks <=> 10.0.0.500:15:33: DYNDNSUPD: Sleeping for 3 seconds waiting for interface Ethernet1 configuration to settle00:15:36: DDNS: Enqueuing new DDNS update 'canada_reserved.hacks' <=> 10.0.0.500:15:36: 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.arpa00:15:36: DDNS: Prerequisite: 10.0.0.11.in-addr.arpa. not in use00:15:36: DDNS: Update: add 10.0.0.11.in-addr.arpa. IN PTR canada_reserved.hacks00:15:36: 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 = hacks00:15:36: DDNS: Prerequisite: canada_reserved.hacks not in use00:15:36: DDNS: Update: add canada_reserved.hacks IN A 10.0.0.500:15:36: 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 finished00:15:36: 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 Clientip dhcp client update dns server nonip ddns update method testingddns bothinterface Ethernet1ip dhcp client update dns server noneip ddns update testingip address dhcpend!Configure the DHCP Serverip dhcp pool testnetwork 10.0.0.0 255.0.0.0update dns both override!Enable Debugging on the DHCP ClientRouter# debug ip ddns update00:16:30:%DHCP-6-ADDRESS_ASSIGN: Interface Ethernet1 assigned DHCP address 10.0.0.6, mask 255.0.0.0, hostname canada_reserved00:16:30: DYNDNSUPD: Adding DNS mapping for canada_reserved.hacks <=> 10.0.0.600:16:30: DYNDNSUPD: Sleeping for 3 seconds waiting for interface Ethernet1 configuration to settle00:16:33: DHCPC: Server performed both updatesSample 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 Clientip dhcp client update dns server nonip ddns update method testingddns bothinterface Ethernet1ip dhcp client update dns server noneip ddns update testing host 172.19.192.32ip address dhcpend!Configure the DHCP Serverip dhcp pool testnetwork 10.0.0.0 255.0.0.0update dns!Enable Debugging on the DHCP ClientRouter# debug ip ddns update00:17:52:%DHCP-6-ADDRESS_ASSIGN: Interface Ethernet1 assigned DHCP address 10.0.0.7, mask 255.0.0.0, hostname canada_reserved00:17:52: DYNDNSUPD: Adding DNS mapping for canada_reserved.hacks <=> 10.0.0.600:17:52: DYNDNSUPD: Sleeping for 3 seconds waiting for interface Ethernet1 configuration to settle00:17:55: DDNS: Enqueuing new DDNS update 'canada_reserved.hacks' <=> 10.0.0.700:17:55: DYNDNSUPD: Adding DNS mapping for canada_reserved.hacks <=> 10.0.0.7 server 10.19.192.3200:17:55: DDNS: Enqueuing new DDNS update 'canada_reserved.hacks' <=> 10.0.0.7 server 10.19.192.3200:17:55: 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.arpa00:17:55: DDNS: Prerequisite: 10.0.0.11.in-addr.arpa. not in use00:17:55: DDNS: Update: add 10.0.0.11.in-addr.arpa. IN PTR canada_reserved.hacks00:17:55: DDNS: Zone name for '10.0.0.11.in-addr.arpa.' is '10.in-addr.arpa'00:17:55: DDNS: Using server 10.19.192.3200:17:55: DDNS: Dynamic Update 1: (sending to server 10.19.192.32)00:17:55: DDNS: Zone = 10.in-addr.arpa00:17:55: DDNS: Prerequisite: 10.0.0.11.in-addr.arpa. not in use00:17:55: DDNS: Update: add 10.0.0.11.in-addr.arpa. IN PTR canada_reserved.hacks00:17:55: 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.arpa00:17:55: DDNS: Update: delete 10.0.0.11.in-addr.arpa. all PTR RRs00:17:55: DDNS: Update: add 10.0.0.11.in-addr.arpa. IN PTR canada_reserved.hacks00:17:55: 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 = hacks00:17:55: DDNS: Prerequisite: canada_reserved.hacks not in use00:17:55: DDNS: Update: add canada_reserved.hacks IN A 10.0.0.700:17:55: 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 finished00:17:55: 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 10.19.192.3200:17:55: DDNS: Dynamic Update 1: (sending to server 10.19.192.32)00:17:55: DDNS: Zone = hacks00:17:55: DDNS: Prerequisite: canada_reserved.hacks not in use00:17:55: DDNS: Update: add canada_reserved.hacks IN A 10.0.0.700:17:55: 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 = hacks00:17:55: DDNS: Update: delete canada_reserved.hacks all A RRs00:17:55: DDNS: Update: add canada_reserved.hacks IN A 10.0.0.700:17:55: 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 finished00:17:55: 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 hacksip ddns update method testinternalinterface ethernet0/0ip ddns update test hostname test2ip addr dhcp!Enable DebuggingRouter# 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 <=> 10.0.0.5Using the show hosts command displays the newly added host table entry.
Router# show hostsDefault domain is hacksName/address lookup uses domain serviceName servers are 255.255.255.255Codes: UN - unknown, EX - expired, OK - OK,?? - revalidatetemp - temporary, perm - permanentNA - Not Applicable None - Not definedHost Port Flags Age Type Address(es)test2.hacks None (perm, OK) 0 IP 10.0.0.5Shutting down the interface removes the host table entry.
interface ethernet0/0shutdown*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 <=> 10.0.0.5The show hosts command output shows the entry has been removed.
Router# show hostsDefault domain is hacksName/address lookup uses domain serviceName servers are 255.255.255.255Codes: UN - unknown, EX - expired, OK - OK,?? - revalidatetemp - temporary, perm - permanentNA - Not Applicable None - Not definedHost 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 the new dyndns update method should be used for Ethernet 1 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 Clientip ddns update method dyndnshttpadd http://test:test@<s>/nic/update?system=dyndns&hostname=<h>&myip=<a>interval max 28 0 0 0interface ethernet1ip ddns update hostname test.dyndns.orgip ddns update dyndns host members.dyndns.orgip addr dhcp!Enable DebuggingRouter# debug ip ddns update00:04:35:%DHCP-6-ADDRESS_ASSIGN: Interface Ethernet1 assigned DHCP address 10.32.254.187, mask 255.255.255.240, hostname test.dyndns.org00:04:35: DYNDNSUPD: Adding DNS mapping for test.dyndns.org <=> 10.32.254.187 server 10.208.196.9400:04:35: DYNDNSUPD: Sleeping for 3 seconds waiting for interface Ethernet1 configuration to settle00:04:38: HTTPDNS: Update add called for test.dyndns.org <=> 10.32.254.18700:04:38: HTTPDNS: Update called for test.dyndns.org <=> 10.32.254.18700:04:38: HTTPDNS: init00:04:38: HTTPDNSUPD: Session ID = 0x700:04:38: 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 request00:04:40: HTTPDNSUPD: Response for update test.dyndns.org <=> 10.32.254.18700:04:40: HTTPDNSUPD: DATA STARTgood 10.32.254.18700:04:40: HTTPDNSUPD: DATA END, Status is Response data received, successfully00:04:40: HTTPDNSUPD: Call returned SUCCESS for update test.dyndns.org <=> 10.32.254.18700:04:40: HTTPDNSUPD: Freeing response00:04:40: 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 10.208.196.9400:05:39: HTTPDNS: Update add called for test.dyndns.org <=> 10.32.254.18700:05:39: HTTPDNS: Update called for test.dyndns.org <=> 10.32.254.18700:05:39: HTTPDNS: init00:05:39: HTTPDNSUPD: Session ID = 0x800:05:39: 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 request00:05:39: HTTPDNSUPD: Response for update test.dyndns.org <=> 10.32.254.18700:05:39: HTTPDNSUPD: DATA STARTnochg 10.32.254.18700:05:39: HTTPDNSUPD: DATA END, Status is Response data received, successfully00:05:39: HTTPDNSUPD: Call returned SUCCESS for update test.dyndns.org <=> 10.32.254.18700:05:39: HTTPDNSUPD: Freeing response00:05:39: DYNDNSUPD: Another update completed (outstanding=0, total=0)00:05:39: HTTPDNSUPD: Clearing all session 8 infoConfiguration 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 the result of forward DNS updates being done by the client and reverse updates done by server for Ethernet interface 1 and Ethernet interface 2 will have both forward and reverse updates done by the server.
interface ethernet1ip dhcp client update dns forward reverseip address dhcp!interface ethernet2ip address dhcpThe 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 overrideip dhcp pool abcnetwork 10.1.0.0 255.255.0.0!update dns never!ip dhcp pool defnetwork 10.10.0.0 255.255.0.0Configuration 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 bothip 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 Configurationip dhcp pool mypoolnetwork 10.10.10.0 255.255.255.0default-router 10.10.10.1!!VPDN configuration for PPPoEvpdn enable!vpdn-group pppoeaccept-dialinprotocol pppoevirtual-template 1!interface Loopback0ip 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 FastEthernet0/0ip address 10.0.58.71 255.255.255.0!!Port under test.!interface FastEthernet0/1no ip addresspppoe enable!!Virtual template and address pool config for PPPoE.interface Virtual-Template1ip unnumbered Loopback0ip mtu 1492peer default ip address dhcp-pool mypoolppp authentication chapThe 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 FastEthernet0/1no 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 mytestddnshttpadd http://test:test@members.dyndns.org/nic/update?system=dyndns&hostname=<h>&myip=<a>
interval maximum 1 0 0 0exitinterface ether1ip ddns update hostname abc.dyndns.org
ip ddns update mytestThe 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 TitleDNS servers and clients configuration tasks
"Configuring DNS Servers" chapter of the Network Registrar User Guide on Cisco.com
"Configuring DHCP" chapter of the IP Addressing and Services Configuration Guide
DHCP commands: complete command syntax, command mode, command history, defaults, usage guidelines, and examples
Cisco IOS IP Command Reference, Volume 1 of 4: Addressing and Services, Release 12.3T
Standards
Standards TitleNo new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.
—
MIBs
RFCs
RFCs TitleRFC 2136
Dynamic Updates in the Domain Name System (DNS Update)
RFC 3007
Secure Domain Name System (DNS) Dynamic Update
Technical Assistance
Command Reference
This section documents new commands only.
debug ip ddns update
To enable debugging for Dynamic Domain Name System (DDNS) updates, use the debug ip ddns update command in privileged EXEC mode. To disable the debugging, use the no form of this command.
debug ip ddns update
no debug ip ddns update
Syntax Description
This command has no arguments or keywords.
Command Modes
Privileged EXEC
Command History
Examples
Use the debug ip ddns update command to verify that your configurations are working properly. The following sample configurations are shown for demonstration of possible debug output that could display for each configuration.
Sample Configuration for the Client to Update A RRs and the Server to Update PTR RRs
The following scenario has a client configured for IETF DDNS updating of address (A) Resource Records (RRs) during which a Dynamic Host Configuration Protocol (DHCP) server is expected to update the pointer (PTR) RR. The DHCP client discovers the domain name system (DNS) server to update using an Start of Authority (SOA) RR lookup since the IP address to the server to update is not specified. The DHCP client is configured to include an fully qualified domain name (FQDN) DHCP option and notifies the DHCP server that it will be updating the A RRs.
!Configure the DHCP Clientip ddns update method testingddnsinterface Ethernet1ip dhcp client update dnsip ddns update testingip address dhcpend!Configure the DHCP Serverip dhcp pool testnetwork 10.0.0.0 255.0.0.0update dns!Enable DebuggingRouter# debug ip ddns update00:14:39:%DHCP-6-ADDRESS_ASSIGN: Interface Ethernet1 assigned DHCP address 10.0.0.4, mask 255.0.0.0, hostname canada_reserved00:14:39: DYNDNSUPD: Adding DNS mapping for canada_reserved.hacks <=> 10.0.0.400:14:39: DYNDNSUPD: Sleeping for 3 seconds waiting for interface Ethernet1 configuration to settle00:14:42: DHCPC: Server performed PTR update00:14:42: DDNS: Enqueuing new DDNS update 'canada_reserved.hacks' <=> 10.0.0.400:14:42: 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 = hacks00:14:42: DDNS: Prerequisite: canada_reserved.hacks not in use00:14:42: DDNS: Update: add canada_reserved.hacks IN A 10.0.0.400:14:42: 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 finished00:14:42: DYNDNSUPD: Another update completed (total outstanding=0)Sample Configuration for the Client to Update Both A and DNS RRs and the Server to Update Neither
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 to not update either A or PTR RRs.
!Configure the DHCP Clientip dhcp-client update dns server noneip ddns update method testingddns bothinterface Ethernet1ip ddns update testingip address dhcpend!Configure the DHCP Serverip dhcp pool testnetwork 10.0.0.0 255.0.0.0update dns!Enable DebuggingRouter# debug ip ddns update00:15:33:%DHCP-6-ADDRESS_ASSIGN: Interface Ethernet1 assigned DHCP address 10.0.0.5, mask 255.0.0.0, hostname canada_reserved00:15:33: DYNDNSUPD: Adding DNS mapping for canada_reserved.hacks <=> 10.0.0.500:15:33: DYNDNSUPD: Sleeping for 3 seconds waiting for interface Ethernet1 configuration to settle00:15:36: DDNS: Enqueuing new DDNS update 'canada_reserved.hacks' <=> 10.0.0.500:15:36: DDNS: Zone name for '11.0.0.11.in-addr.arpa.' is '11.in-addr.arpa'00:15:36: DDNS: Dynamic Update 1: (sending to server 10.19.192.32)00:15:36: DDNS: Zone = 11.in-addr.arpa00:15:36: DDNS: Prerequisite: 5.0.0.11.in-addr.arpa. not in use00:15:36: DDNS: Update: add 5.0.0.11.in-addr.arpa. IN PTR canada_reserved.hacks00:15:36: 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 = hacks00:15:36: DDNS: Prerequisite: canada_reserved.hacks not in use00:15:36: DDNS: Update: add canada_reserved.hacks IN A 10.0.0.500:15:36: 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 finished00:15:36: DYNDNSUPD: Another update completed (total outstanding=0)Sample Configuration for the Client to Update A and DNS RRs and the Server to Update Neither
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 explicitly specifies the server to update. The DHCP client is configured to include an FQDN DHCP option that instructs the DHCP server not to update either A or PTR RRs. The configuration is performed using the ip dhcp client update dns command. The DHCP server is configured to override the client request and update both A and PTR RR anyway.
!Configure the DHCP Clientip dhcp client update dns server noneip ddns update method testingddns bothinterface Ethernet1ip dhcp client update dns server noneip ddns update testingip address dhcpend!Configure the DHCP Serverip dhcp pool testnetwork 10.0.0.0 255.0.0.0update dns both override!Enable Debugging on the DHCP ClientRouter# debug ip ddns update00:16:30:%DHCP-6-ADDRESS_ASSIGN: Interface Ethernet1 assigned DHCP address 10.0.0.6, mask 255.0.0.0, hostname canada_reserved00:16:30: DYNDNSUPD: Adding DNS mapping for canada_reserved.hacks <=> 10.0.0.600:16:30: DYNDNSUPD: Sleeping for 3 seconds waiting for interface Ethernet1 configuration to settle00:16:33: DHCPC: Server performed both updatesSample Configuration for the Client to Update A and DNS RRs and the Server to Update Neither
The following scenario has the client 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 which instructs the DHCP server not to update either A or PTR RRs. The DHCP server is configured to allow the client to update whatever RR it chooses.
!Configure the DHCP Clientip dhcp client update dns server nonip ddns update method testingddns bothinterface Ethernet1ip dhcp client update dns server noneip ddns update testing host 172.19.192.32ip address dhcpend!Configure the DHCP Serverip dhcp pool testnetwork 11.0.0.0 255.0.0.0update dns!Enable Debugging on the DHCP ClientRouter# 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_reserved00:17:52: DYNDNSUPD: Adding DNS mapping for canada_reserved.hacks <=> 10.0.0.600:17:52: DYNDNSUPD: Sleeping for 3 seconds waiting for interface Ethernet1 configuration to settle00:17:55: DDNS: Enqueuing new DDNS update 'canada_reserved.hacks' <=> 10.0.0.700:17:55: DYNDNSUPD: Adding DNS mapping for canada_reserved.hacks <=> 10.0.0.7 server 10.19.192.3200:17:55: DDNS: Enqueuing new DDNS update 'canada_reserved.hacks' <=> 10.0.0.7 server 10.19.192.3200:17:55: DDNS: Zone name for '7.0.0.11.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 = 11.in-addr.arpa00:17:55: DDNS: Prerequisite: 7.0.0.11.in-addr.arpa. not in use00:17:55: DDNS: Update: add 7.0.0.11.in-addr.arpa. IN PTR canada_reserved.hacks00:17:55: DDNS: Zone name for '7.0.0.11.in-addr.arpa.' is '11.in-addr.arpa'00:17:55: DDNS: Using server 10.19.192.3200:17:55: DDNS: Dynamic Update 1: (sending to server 10.19.192.32)00:17:55: DDNS: Zone = 11.in-addr.arpa00:17:55: DDNS: Prerequisite: 7.0.0.11.in-addr.arpa. not in use00:17:55: DDNS: Update: add 7.0.0.11.in-addr.arpa. IN PTR canada_reserved.hacks00:17:55: 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 = 11.in-addr.arpa00:17:55: DDNS: Update: delete 7.0.0.11.in-addr.arpa. all PTR RRs00:17:55: DDNS: Update: add 7.0.0.11.in-addr.arpa. IN PTR canada_reserved.hacks00:17:55: 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 = hacks00:17:55: DDNS: Prerequisite: canada_reserved.hacks not in use00:17:55: DDNS: Update: add canada_reserved.hacks IN A 10.0.0.700:17:55: 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 finished00:17:55: 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 10.19.192.3200:17:55: DDNS: Dynamic Update 1: (sending to server 10.19.192.32)00:17:55: DDNS: Zone = hacks00:17:55: DDNS: Prerequisite: canada_reserved.hacks not in use00:17:55: DDNS: Update: add canada_reserved.hacks IN A 10.0.0.700:17:55: 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 = hacks00:17:55: DDNS: Update: delete canada_reserved.hacks all A RRs00:17:55: DDNS: Update: add canada_reserved.hacks IN A 10.0.0.700:17:55: 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 finished00:17:55: DYNDNSUPD: Another update completed (total outstanding=0)Sample Configuration for Updating the Internal Host Table
In the following scenario, the debug output displays the internal host table updates when the default domain name is hacks. The update method named test specifies that the internal Cisco IOS software host table should be updated. Configuring the update method as "test" should be used when the address on the Ethernet interface 0/0 changes. The hostname is configured for the update on this interface.
!Configure the Host Table Updatesip domain name hacksip ddns update method testinternalinterface ethernet0/0ip ddns update test hostname test2ip addr dhcp!Enable DebuggingRouter# 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 <=> 10.0.0.5Using the show hosts command displays the newly added host table entry.
Router# show hostsDefault domain is hacksName/address lookup uses domain serviceName servers are 255.255.255.255Codes: UN - unknown, EX - expired, OK - OK,? - revalidatetemp - temporary, perm - permanentNA - Not Applicable None - Not definedHost Port Flags Age Type Address(es)test2.hacks None (perm, OK) 0 IP 10.0.0.5Shutting down the interface removes the host table entry.
interface ethernet0/0shutdown*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 <=> 10.0.0.5Using the show hosts command confirms that the entry has been removed.
Router# show hostsDefault domain is hacksName/address lookup uses domain serviceName servers are 255.255.255.255Codes: UN - unknown, EX - expired, OK - OK,? - revalidatetemp - temporary, perm - permanentNA - Not Applicable None - Not definedSample Configuration of HTTP DDNS Updates
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, which specifies that updates should be sent at least every 28 days. Configuring the new "dyndns" update method should be used for Ethernet interface 1.
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 Clientip ddns update method dyndnshttpadd http://test:test@<s>/nic/update?system=dyndns&hostname=<h>&myip=<a>interval max 28 0 0 0interface ethernet1ip ddns update hostname test.dyndns.orgip ddns update dyndns host members.dyndns.orgip addr dhcp!Enable DebuggingRouter# debug ip ddns update00:04:35:%DHCP-6-ADDRESS_ASSIGN: Interface Ethernet1 assigned DHCP address 10.32.254.187, mask 255.255.255.240, hostname test.dyndns.org00:04:35: DYNDNSUPD: Adding DNS mapping for test.dyndns.org <=> 10.32.254.187 server 10.208.196.9400:04:35: DYNDNSUPD: Sleeping for 3 seconds waiting for interface Ethernet1 configuration to settle00:04:38: HTTPDNS: Update add called for test.dyndns.org <=> 10.32.254.18700:04:38: HTTPDNS: Update called for test.dyndns.org <=> 10.32.254.18700:04:38: HTTPDNS: init00:04:38: HTTPDNSUPD: Session ID = 0x700:04:38: 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 request00:04:40: HTTPDNSUPD: Response for update test.dyndns.org <=> 10.32.254.18700:04:40: HTTPDNSUPD: DATA STARTgood 10.32.254.18700:04:40: HTTPDNSUPD: DATA END, Status is Response data received, successfully00:04:40: HTTPDNSUPD: Call returned SUCCESS for update test.dyndns.org <=> 10.32.254.18700:04:40: HTTPDNSUPD: Freeing response00:04:40: 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 10.208.196.9400:05:39: HTTPDNS: Update add called for test.dyndns.org <=> 10.32.254.18700:05:39: HTTPDNS: Update called for test.dyndns.org <=> 10.32.254.18700:05:39: HTTPDNS: init00:05:39: HTTPDNSUPD: Session ID = 0x800:05:39: 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 request00:05:39: HTTPDNSUPD: Response for update test.dyndns.org <=> 10.32.254.18700:05:39: HTTPDNSUPD: DATA STARTnochg 10.32.254.18700:05:39: HTTPDNSUPD: DATA END, Status is Response data received, successfully00:05:39: HTTPDNSUPD: Call returned SUCCESS for update test.dyndns.org <=> 10.32.254.18700:05:39: HTTPDNSUPD: Freeing response00:05:39: DYNDNSUPD: Another update completed (outstanding=0, total=0)00:05:39: HTTPDNSUPD: Clearing all session 8 infoTable 1 describes the significant fields shown in the output.
Related Commands
host (host-list)
To specify a list of hosts that will receive Dynamic Domain Name System (DDNS) updates of address (A) and pointer (PTR) Resource Records (RRs), use the host command in host-list configuration mode. To disable the host list, use the no form of this command.
host [vrf vrf-name] {host-ip-address | hostname}
no host [vrf vrf-name] {host-ip-address | hostname}
Syntax Description
Defaults
No list is configured for hosts.
Command Modes
Host-list configuration
Command History
Examples
The following example shows how to configure a list of hosts:
ip host-list testhost vrf abc 10.10.0.0Related Commands
ip ddns update hostname
To enable a host to be used for Dynamic Domain Name System (DDNS) updates of address (A) and pointer (PTR) resource records (RRs), use the ip ddns update hostname command in interface configuration mode. To disable the dynamic updates, use the no form of this command.
ip ddns update hostname hostname
no ip ddns update hostname hostname
Syntax Description
Defaults
No host is configured.
Command Modes
Interface configuration
Command History
Usage Guidelines
Note The interface configuration overrides the global configuration.
Examples
The following example shows how to configure the testhost host to update A and PTR RRs:
interface ethernet1/0ip ddns update testhostRelated Commands
ip ddns update method
To specify a method of Dynamic Domain Name System (DDNS) updates of address (A) and pointer (PTR) Resource Records (RRs) and the maximum interval, use the ip ddns update method command in global configuration mode. To disable dynamic updates, use the no form of this command.
ip ddns update method method-name {ddns [both] | http {add url-string | remove url-string} | internal name-cache} interval maximum days hours minutes seconds
no ip ddns update method method-name {ddns [both] | http {add url-string | remove url-string} | internal} interval maximum days hours minutes seconds
Syntax Description
Defaults
No DDNS update method is configured.
Command Modes
Global configuration
Command History
Usage Guidelines
The interface configuration overrides the global configuration.
Examples
The following example shows how to configure the DHCP server to perform A and PTR RR updates and to override the DHCP client FQDN option:
ip ddns update method unit-test ddns both interval maximum 3 2 15 30The 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 mytestddnshttpadd http://test:test@members.dyndns.org/nic/update?system=dyndns&hostname=<h>&myip=<a>
interval maximum 1 0 0 0exitinterface ethernet1ip ddns update hostname abc.dyndns.org
ip ddns update mytestThe 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:
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.
Related Commands
ip dhcp client update dns
To enable Dynamic Domain Name System (DDNS) updates of address (A) resource records (RRs) using the same hostname passed in the hostname and fully qualified domain name (FQDN) options by a client, use the ip dhcp client update dns command in interface configuration mode. To disable dynamic updates of A RRs, use the no form of this command.
ip dhcp client update dns [server {reverse | both | none}]
no ip dhcp client update dns [server {reverse | both | none}]
Syntax Description
Defaults
If no server keywords are specified, then the reverse keyword is the default.
Command Modes
Interface configuration
Command History
Usage Guidelines
Commands that are configured in interface configuration mode override the commands configured using global configuration mode. The ip dhcp-client update dns command (hyphenated) is the global configuration command.
If you specify the both and none keywords in separate configurations, the DHCP client will update both the A and PTR RRs, and the DHCP server will not perform any updates. If you specify the none and both keywords (in this order), the DHCP client will not perform any updates and the server will update both the A and PTR RRs.
You cannot specify the both and reverse keywords together.
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 tell the server to update "reverse" (the default), "both," or "none." 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.
Even if the client tells 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 the 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 tell 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.
Examples
The following example shows how to configure the DHCP client to perform A and PTR RR updates, but the DHCP server will not perform the updates:
ip dhcp client update dns server noneRelated Commands
ip dhcp-client update dns
To enable Dynamic Domain Name System (DDNS) updates of address (A) resource records (RRs) using the same hostname passed in the hostname and fully qualified domain name (FQDN) options by a client, use the ip dhcp-client update dns command in global configuration mode. To disable dynamic updates, use the no form of this command.
ip dhcp-client update dns [server {reverse | both | none}]
no ip dhcp client update dns
Syntax Description
Defaults
If no server keywords are specified, then the reverse keyword is the default.
Command Modes
Global configuration
Command History
Usage Guidelines
Commands that are configured in interface configuration mode override the commands configured using global configuration mode. The ip dhcp client update dns command (no hyphen) is the interface configuration command.
If you specify the both and none keywords, the DHCP client will update both the A and PTR RRs, and the DHCP server will not perform any updates. The DHCP server can override the DHCP client using the ip dhcp update dns override command.
If you specify the none and both keywords (in this order), the DHCP client will not perform any updates and the server will update both the A and PTR RRs.
You cannot specify the both and reverse keywords or both and both keywords.
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 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 tell the server to update "reverse" (the default), "both", or "none." Obviously, if the ip ddns update method command is configured with the ddns both keyword combination, 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 tells 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 tell 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.
Examples
The following example shows how to configure the DHCP server to perform A and PTR RR updates:
ip dhcp-client update dns server bothRelated Commands
ip dhcp update dns
To enable Dynamic Domain Name System (DDNS) updates of address (A) and pointer (PTR) resource records (RRs) for most address pools, use the ip dhcp update dns command in global configuration mode. To disable dynamic updates, use the no form of this command.
ip dhcp update dns [both] [override] [before]
no ip dhcp update dns [both] [override] [before]
Syntax Description
Defaults
Perform DDNS updates after sending a DHCP ACK.
Command Modes
Global configuration
Command History
Usage Guidelines
Some address pools are configured using the update dns command, and that configuration overrides the global configuration. See the update dns command for more information.
If you specify the both and override keywords, the DHCP server will perform the updates for both A and PTR RRs overriding anything that the DHCP client has specified in the FQDN option.
Examples
The following example shows how to configure the DHCP server to perform A and PTR RR updates and to override the DHCP client FQDN option:
ip dhcp update dns both overrideRelated Commands
ip host-list
To specify a list of hosts that will receive Dynamic Domain Name System (DDNS) updates of address (A) and pointer (PTR) resource records (RRs), use the ip host-list command in interface configuration mode. To disable the host list, use the no form of this command.
ip host-list host-list-name [vrf vrf-name]
no ip host-list host-list-name [vrf vrf-name]
Syntax Description
Defaults
No IP host list is configured.
Command Modes
Interface configuration
Command History
Usage Guidelines
The interface configuration overrides the global configuration.
Examples
The following example shows how to configure a list of hosts:
ip host-list testhost vrf testgroupRelated Commands
show ip ddns update
To display information about the Dynamic Domain Name System (DDNS) updates, use the show ip ddns update command in privileged EXEC mode.
show ip ddns update [interface]
Syntax Description
Command Modes
Privileged EXEC
Command History
Examples
The following output shows the IP DDNS update method on loopback interface 100 and the destination:
Router# show ip ddns updateDynamic DNS Update on Loopback100:Update Method Name Update Destinationtesting 10.1.2.3Related Commands
show ip ddns update method
To display information about the Dynamic Domain Name System (DDNS) update method, use the show ip ddns update method command in privileged EXEC mode.
show ip ddns update method [method-name]
Syntax Description
Command Modes
Privileged EXEC
Command History
Examples
The following example shows how to display the DDNS updates for an internal name cache method:
Router# show ip ddns update methodDynamic DNS Update Method: testDynamic DNS update in IOS internal name cacheRelated Commands
show ip dhcp server pool
To display Dynamic Host Configuration Protocol (DHCP) server pool statistics, use the show ip dhcp server pool command in privileged EXEC mode.
show ip dhcp server pool
Syntax Description
This command has no arguments or keywords.
Command Modes
Privileged EXEC
Command History
Examples
I need some sample output, please?
Related Commands
show ip host-list
To display the assigned hosts in a list, use the show ip host-list command in privileged EXEC mode.
show ip host-list [host-list-name]
Syntax Description
Command Modes
Privileged EXEC
Command History
Examples
The following example shows how to display the host list for the abc-test group:
Router# show ip host-list abctestHost list: abctestddns.abc.test10.2.3.4ddns2.unit.test10.3.4.5ddns3.com10.3.3.3e.org1.org.2.org3.com10.5.5.5 (VRF: green)Related Commands
update dns
To dynamically update the Domain Name System (DNS) with address (A) and pointer (PTR) Resource Records (RRs) for some address pools, use the update dns command in global configuration mode. To disable dynamic updates, use the no form of this command.
update dns [both | never] [override] [before]
no update dns [both | never] [override] [before]
Syntax Description
Defaults
No updates are performed.
Command Modes
Global configuration
Command History
Usage Guidelines
If you configure the update dns both override command, the DHCP server will perform DDNS updates for both PTR and A RRs associated with addresses assigned from an address pool, even if the DHCP client specified in the FQDN that the server should not.
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.
Examples
The following example shows how to configure the DHCP to never update the A and PTR RRs:
update dns neverRelated Commands
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