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Cisco IOS IP Addressing Services Command Reference
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Introduction
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ARP Commands
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DHCP Commands: accounting (DHCP) through ip dhcp excluded-address
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DHCP Commands: ip dhcp limit lease through lease
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DHCP Commands: netbios-name-server through vrf (DHCP pool)
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DNS Commands: ddns (DDNS-update-method) through ip dns server queue limit
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DNS Commands: ip dns spoofing through view (DNS)
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IP Addressing Commands
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NAT Commands
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NHRP Commands
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Table Of Contents
dns forwarding source-interface
domain resolver source-interface
DNS Commands
ddns (DDNS-update-method)
To specify an update method for address (A) Resource Records (RRs) as IETF standardized Dynamic Domain Name System (DDNS), use the ddns command in DDNS-update-method configuration mode. To disable the DDNS method for updating, use the no form of this command.
ddns [both]
no ddns
Syntax Description
Defaults
No DDNS updating is configured.
Command Modes
DDNS-update-method configuration
Command History
12.3(8)YA
This command was introduced.
12.3(14)T
This command was integrated into Cisco IOS Release 12.3(14)T.
Usage Guidelines
If Dynamic Host Configuration Protocol (DHCP) is used to configure the IP address on the interface, a DHCP client may not perform both A and PTR RRs or any updates. Also, if the DHCP server notifies the client during the DHCP interaction that it will perform the updates, then the DHCP client will not perform the updates. The DHCP server can always override the client even if the client is configured to perform the updates.
If the interface is configured using DHCP and if the DDNS update method is configured on that interface, then the DHCP fully qualified domain name (FQDN) option is included in the DHCP packets between the client and the server. The FQDN option contains the hostname, which is used in the update as well as information about what types of updates the client has been configured to perform.
If the ddns keyword is specified, the A RRs only are updated, but if the ddns both keyword are specified, both the A and the PTR RRs are updated. Also, if the DHCP server returns the the FQDN option with an updated hostname, that hostname is used in the update instead.
Examples
The following example shows how to configure a DHCP server to perform both A and PTR RR updates:
ip ddns update method unit-testddns bothRelated Commands
ip ddns update method
Enables DDNS as the update method and assigns a method name.
dns forwarder
To add an address to the end of the ordered list of IP addresses for a Domain Name System (DNS) view to use when forwarding incoming DNS queries, use the dns forwarder command in DNS view configuration mode. To remove an IP address from the list, use the no form of this command.
dns forwarder [vrf vrf-name] forwarder-ip-address
no dns forwarder [vrf vrf-name] forwarder-ip-address
Syntax Description
Command Default
Provided that DNS forwarding (configured by using the dns forwarding command) is enabled and the interface to use when forwarding incoming DNS queries is configured (if using the dns forwarding source-interface command) and not shut down, incoming DNS queries handled using the DNS view are forwarded to one of the DNS forwarding name servers.
If no forwarding name servers are configured for the DNS view, the router uses any configured domain name server addresses.
If there are no domain name server addresses configured either, the router forwards incoming DNS queries to the limited broadcast address (255.255.255.255) so that the queries are received by all hosts on the local network segment but not forwarded by routers.
Command Modes
DNS view configuration
Command History
Usage Guidelines
This command can be entered multiple times to specify a maximum of six forwarding name servers. After six forwarding name servers have been specified, additional forwarding name servers cannot be specified unless an existing entry is removed.
To display the list of DNS forwarding name server addresses configured for the DNS view, use the show ip dns view command.
Note
DNS resolving name servers and DNS forwarding name servers are configured separately. The domain name-server and domain name-server interface commands are used to specify the DNS resolving name servers (the ordered list of IP addresses to use when resolving internally generated DNS queries handled using the DNS view). The dns forwarder command specifies the forwarder addresses (the ordered list of IP addresses to use when forwarding incoming DNS queries handled using the DNS view).
Versions of Cisco IOS prior to Release 12.4(9)T used the resolving name server list for both resolving internal DNS queries and forwarding DNS queries received by the DNS server. For backward compatibility, if there are no forwarding name servers configured, the resolving name server list will be used instead.Examples
The following example shows how to add three IP addresses to the list of forwarder addresses for the DNS view named user3 that is associated with the VRF vpn32:
Router(config)# ip dns view vrf vpn32 user3Router(cfg-dns-view)# dns forwarder 192.168.2.0Router(cfg-dns-view)# dns forwarder 192.168.2.1Router(cfg-dns-view)# dns forwarder 192.168.2.2The following example shows how to add the IP address 192.0.2.3 to the list of forwarder addresses for the DNS view named user1 that is associated with the VRF vpn32, with the restriction that incoming DNS queries will be forwarded to 192.0.2.3 only if the queries are from the VRF named vpn1:
Router(config)# ip dns view vrf vpn32 user1Router(cfg-dns-view)# dns forwarder vrf vpn1 192.168.2.3Related Commands
dns forwarding
To enable forwarding of incoming Domain Name System (DNS) queries handled using the DNS view, use the dns forwarding command in DNS view configuration mode. To disable forwarding and revert to the default configuration, use the no form of this command.
dns forwarding [retry number | timeout seconds]
no dns forwarding [retry | timeout]
Syntax Description
Command Default
The default value is inherited from the global setting configured using the ip domain lookup global configuration command. However, the dns forwarding command for the DNS view does not have a reciprocal side effect on the setting configured by the ip domain lookup command.
Command Modes
DNS view configuration (cfg-dns-view)
Command History
12.4(9)T
This command was introduced.
15.0(1)M
This command was modified. The retry number and timeout seconds keywords and arguments were added.
Usage Guidelines
This command enables forwarding of incoming DNS queries handled using the DNS view.
To display the DNS forwarding setting for a DNS view, use the show ip dns view command.
If you configure the no domain lookup command for a DNS view while the dns forwarding command has not been disabled for that view, then the dns forwarding command setting will appear in the show ip dns view command output in order to make it clear that DNS forwarding is still enabled.
If you configure the no ip domain lookup global configuration command, however, the no dns forwarding setting is automatically configured also, in order to be backward compatible with the global command form.
Note
By default, domain lookup and DNS forwarding are both enabled for a view. If you then configure the no domain lookup command, DNS forwarding is still enabled. However, if you instead use the older Cisco IOS command no ip domain lookup to disable domain lookup for the global default view, then DNS forwarding is disabled automatically. This is done for backward compatibility with the functionality of the no ip domain lookup global configuration command.Examples
The following example shows how to enable forwarding of incoming DNS queries handled using the DNS view named user3 that is associated with the VRF vpn32:
Router(config)# ip dns view vrf vpn32 user3Router(cfg-dns-view)# dns forwardingRelated Commands
dns forwarding source-interface
To specify the interface to use when forwarding incoming Domain Name System (DNS) queries handled using the DNS view, use the dns forwarding source-interface command in DNS view configuration mode. To remove the specification of the source interface for a DNS view to use when forwarding DNS queries, use the no form of this command.
dns forwarding source-interface interface
no dns forwarding source-interface
Syntax Description
Command Default
No interface is specified for forwarding incoming DNS queries handled using the DNS view, so the router selects the appropriate source IP address automatically, according to the interface used to send the packet, when the query is forwarded.
Command Modes
DNS view configuration
Command History
Usage Guidelines
This command specifies the interface to use when forwarding incoming DNS queries handled using the DNS view.
To display the interface configured by this command, use the show ip dns view command.
Tip
Examples
The following is sample output from the show interfaces command used with the summary keyword:
Router# show interfaces summary*: interface is upIHQ: pkts in input hold queue IQD: pkts dropped from input queueOHQ: pkts in output hold queue OQD: pkts dropped from output queueRXBS: rx rate (bits/sec) RXPS: rx rate (pkts/sec)TXBS: tx rate (bits/sec) TXPS: tx rate (pkts/sec)TRTL: throttle countInterface IHQ IQD OHQ OQD RXBS RXPS TXBS TXPS TRTL------------------------------------------------------------------------* FastEthernet0/0 0 0 0 0 0 0 0 0 0FastEthernet0/1 0 0 0 0 0 0 0 0 0ATM2/0 0 0 0 0 0 0 0 0 0Ethernet3/0 0 0 0 0 0 0 0 0 0Ethernet3/1 0 0 0 0 0 0 0 0 0Ethernet3/2 0 0 0 0 0 0 0 0 0Ethernet3/3 0 0 0 0 0 0 0 0 0ATM6/0 0 0 0 0 0 0 0 0 0NOTE:No separate counters are maintained for subinterfacesHence Details of subinterface are not shownThe following example shows how to configure FastEthernet slot 0, port 1 as the interface to be used to forward DNS queries for the DNS view named user3 that is associated with the VRF vpn32:
Router(config)# ip dns view vrf vpn32 user3Router(cfg-dns-view)# dns forwarder source-interface FastEthernet0/1Related Commands
domain list
To add a domain name to the end of the ordered list of domain names used to complete unqualified hostnames (names without a dotted-decimal domain name) in Domain Name System (DNS) queries handled using the DNS view, use the domain list command in DNS view configuration mode. To remove a name from the domain search list, use the no form of this command.
domain list domain-name
no domain list domain-name
Syntax Description
domain-name
Domain name to add or delete from the domain search list.
Note
Command Default
No domain list is defined for the DNS view.
Command Modes
DNS view configuration
Command History
Usage Guidelines
This command adds a domain name to the end of the domain search list for the DNS view.
Note
To display the list of domain names used to complete unqualified hostnames in DNS queries received by a DNS view, use the show hosts command or the show ip dns view command.
Examples
The following example shows how to add two domain names to the list for the DNS view named user3 that is associated with the VRF vpn32:
Router(config)# ip dns view vrf vpn32 user3Router(cfg-dns-view)# domain list example1.comRouter(cfg-dns-view)# domain list example1.orgThe following example shows how to add two domain names to the list for the DNS view and then delete one of the domain names from the list:
Router(cfg-dns-view)# domain list example2.comRouter(cfg-dns-view)# domain list example2.orgRouter(cfg-dns-view)# no domain list example2.netRelated Commands
domain lookup
To enable the IP Domain Name System (DNS)-based hostname-to-address translation for internally generated DNS queries handled using the DNS view, use the domain lookup command in DNS view configuration mode. To disable domain lookup for hostname resolution, use the no form of this command.
domain lookup
no domain lookup
Syntax Description
This command has no arguments or keywords.
Command Default
The default value is inherited from the global setting configured using the ip domain lookup global command. However, the domain lookup DNS view command does not have a reciprocal side effect on the setting configured by the ip domain lookup global command.
Command Modes
DNS view configuration
Command History
Usage Guidelines
This command enables DNS-based hostname-to-address translation for internally generated DNS queries handled using the DNS view.
To display the DNS lookup setting for a DNS view, use the show ip dns view command.
If you configure no dns forwarding for a DNS view while domain lookup has not been disabled for that view, then the domain lookup setting will appear in the show ip dns view command output in order to make it clear that domain lookup is still enabled.
If you configure the no ip domain lookup global command, however, the no domain lookup setting is automatically configured also, in order to be backward compatible with the global command form.
Note
By default, both domain lookup and DNS forwarding are both enabled for a view. If you then configure no domain lookup, DNS forwarding is still enabled. However, if you instead uses the older Cisco IOS command no ip domain lookup to disable domain lookup for the global default view, then DNS forwarding is disabled automatically. This is done for backward compatibility with the functionality of the no ip domain lookup global command.Examples
The following example shows how to enable IP DNS-based hostname-to-address translation in the DNS view named user3 that is associated with the VRF vpn32:
Router(config)# ip dns view vrf vpn32 user3Router(cfg-dns-view)# domain lookupRelated Commands
domain multicast
To configure the domain name to be used when performing multicast address lookups for internally generated Domain Name System (DNS) queries handled using the DNS view, use the domain multicast command in DNS view configuration mode. To remove the specification of the domain name for multicast address lookups, use the no form of this command.
domain multicast domain-name
no domain multicast
Syntax Description
Command Default
No IP address is specified for performing multicast address lookups for the DNS view.
Command Modes
DNS view configuration
Command History
Usage Guidelines
This command configures the domain name to be used when performing multicast address lookups for internally generated DNS queries handled using the DNS view.
To display the domain name for multicast address lookups, use the show ip dns view command.
Examples
The following example shows how to configure the domain name www.example.com as the domain name to be used when performing multicast lookups for internally generated DNS queries handled using the DNS view named user3 that is associated with the VRF vpn32:
Router(config)# ip dns view vrf vpn32 user3Router(cfg-dns-view)# domain multicast www.example.comRelated Commands
domain name
To specify the default domain for a Domain Name System (DNS) view to use to complete unqualified hostnames (names without a dotted-decimal domain name), use the domain name command in DNS view configuration mode. To remove the specification of the default domain name for a DNS view, use the no form of this command.
domain name domain-name
no domain name
Syntax Description
domain-name
Default domain name used to complete unqualified hostnames.
Note
Command Default
No default domain name is defined for the DNS view.
Command Modes
DNS view configuration
Command History
Usage Guidelines
This command configures the default domain name used to complete unqualified hostnames in DNS queries handled using the DNS view.
Note
To display the default domain name configured for a DNS view, use the show hosts command or the show ip dns view command.
Examples
The following example shows how to define example.com as the default domain name for the DNS view named user3 that is associated with the VRF vpn32:
Router(config)# ip dns view vrf vpn32 user3Router(cfg-dns-view)# domain name example.comRelated Commands
domain name-server
To add a name server to the list of Domain Name System (DNS) name servers to be used for a DNS view to resolve internally generated DNS queries, use the domain name-server command in DNS view configuration mode. To remove a DNS name server from the list, use the no form of this command.
domain name-server name-server-ip-address
no domain name-server name-server-ip-address
Syntax Description
Command Default
No IP address is explicitly added to the list of resolving name servers for this view, although an IP address can be added to the list if dynamic name server acquisition is enabled. If the list of resolving name servers is empty, the router will send the query to the limited broadcast address 255.255.255.255 when this view is used.
Command Modes
DNS view configuration
Command History
Usage Guidelines
This command can be entered multiple times to specify a maximum of six resolving name servers. After six resolving name servers have been specified, additional resolving name servers cannot be specified unless an existing entry is removed.
This method of explicitly populating the list of resolving name servers is useful in an enterprise network where the population of available DNS servers is relatively static. In an Internet service provider (ISP) environment, where primary and secondary DNS server addresses can change frequently, the router can learn a DNS server address through either DHCP or PPP on the interface. To configure the dynamic acquisition of DNS resolving name server addresses, use the domain name-server interface command. Regardless of the method or methods used to populate the list of DNS resolving name servers for the view, no more than six resolving name servers are maintained for the view.
To display the list of DNS resolving name server IP addresses configured for a DNS view, use the show hosts command or the show ip dns view command.
Note
If there is no DNS forwarder configuration in a view, then the domain name server list will be used when forwarding DNS queries. This is done for backward compatibility with the ip name-server global command.Examples
The following example shows how to specify the hosts at 192.168.2.111 and 192.168.2.112 as the name servers for the DNS view named user3 that is associated with the VRF vpn32:
Router(config)# ip dns view vrf vpn32 user3Router(cfg-dns-view)# domain name-server 192.168.2.111Router(cfg-dns-view)# domain name-server 192.168.2.112Related Commands
domain name-server interface
To specify the interface on which the router can learn (through either DHCP or PPP) Domain Name System (DNS) a resolving name server address for the DNS view, use the domain name-server interface command in DNS view configuration mode. To remove the definition of the interface, use the no form of this command.
domain name-server interface interface
no domain name-server interface interface
Syntax Description
Command Default
No interface is used to acquire the DHCP or PPP address to be used for a DNS view to resolve internally generated DNS queries.
Command Modes
DNS view configuration
Command History
Usage Guidelines
This command specifies the interface from which to acquire (through DHCP or PPP interaction on the interface) the IP address of a DNS server to add to the list of DNS name servers used to resolve internally generated DNS queries for the DNS view.
The dynamic acquisition of DNS resolving name server addresses is useful in an Internet service provider (ISP) environment, where primary and secondary DNS server addresses can change frequently. To explicitly populate the list of resolving name servers in an enterprise network where the population of available DNS servers is relatively static, use the domain name-server command. Regardless of the method or methods used to populate the list of DNS resolving name servers for the view, no more than six resolving name servers are maintained for the view.
Note
If there is no DNS forwarder configuration in a view, then the domain name server list will be used when forwarding DNS queries. This is done for backward compatibility with the ip name-server global command.
Tip
Examples
The following is sample output from the show interfaces command used with the summary keyword:
Router# show interfaces summary*: interface is upIHQ: pkts in input hold queue IQD: pkts dropped from input queueOHQ: pkts in output hold queue OQD: pkts dropped from output queueRXBS: rx rate (bits/sec) RXPS: rx rate (pkts/sec)TXBS: tx rate (bits/sec) TXPS: tx rate (pkts/sec)TRTL: throttle countInterface IHQ IQD OHQ OQD RXBS RXPS TXBS TXPS TRTL------------------------------------------------------------------------* FastEthernet0/0 0 0 0 0 0 0 0 0 0FastEthernet0/1 0 0 0 0 0 0 0 0 0ATM2/0 0 0 0 0 0 0 0 0 0Ethernet3/0 0 0 0 0 0 0 0 0 0Ethernet3/1 0 0 0 0 0 0 0 0 0Ethernet3/2 0 0 0 0 0 0 0 0 0Ethernet3/3 0 0 0 0 0 0 0 0 0ATM6/0 0 0 0 0 0 0 0 0 0NOTE:No separate counters are maintained for subinterfacesHence Details of subinterface are not shownThe following example shows how to specify a list of name servers for the DNS view named user3 that is associated with the VRF vpn32. First, the list of name server addresses is cleared, then five DNS server IP addresses are added to the list. Finally, FastEthernet slot 0, port 0 is specified as the interface on which to acquire, by DHCP or PPP interaction, a sixth DNS server IP address.
Router(config)# ip dns view vrf vpn32 user3Router(cfg-dns-view)# no domain name-serverRouter(cfg-dns-view)# domain name-server 192.168.2.1Router(cfg-dns-view)# domain name-server 192.168.2.2Router(cfg-dns-view)# domain name-server 192.168.2.3Router(cfg-dns-view)# domain name-server 192.168.2.4Router(cfg-dns-view)# domain name-server 192.168.2.5Router(cfg-dns-view)# domain name-server interface FastEthernet0/0Related Commands
domain resolver source-interface
To set the source IP address of the Domain Name Server (DNS) queries for the DNS resolver functionality, use the domain resolver source-interface command in DNS view configuration mode. To disable the configuration, use the no form of this command.
domain resolver source-interface interface-type number
no domain resolver source-interface
Syntax Description
Command Default
Disabled. (DNS queries are not forwarded through the expected interface.)
Command Modes
DNS view configuration (cfg-dns-view)
Command History
Usage Guidelines
Sometimes, when a source interface is configured on a router with the split DNS feature to forward DNS queries, the router does not forward the DNS queries through the configured interface. If you want the router to forward the DNS queries through a particular source interface, configure the router using the domain resolver source-interface command.
Examples
The following example shows how to set the source IP address of the DNS queries for the DNS resolver functionality:
Router(config)# ip dns view vrf vpn32 user3Router(cfg-dns-view)# domain resolver source-interface fastethernet 0/0Related Commands
ip dns view
Creates the DNS view of the specified name associated with the specified VRF instance and then enters DNS view configuration mode.
domain retry
To configure the number of retries to perform when sending or forwarding Domain Name System (DNS) queries handled using the DNS view, use the domain retry command in DNS view configuration mode. To remove the specification of the number of retries for a DNS view, use the no form of this command.
domain retry number
no domain retry
Syntax Description
Command Default
number: 2 times
Command Modes
DNS view configuration
Command History
Usage Guidelines
This command configures the number of retries to perform when sending or forwarding DNS queries handled using the DNS view.
To display the number of retries configured for the DNS view, use the show ip dns view command.
Examples
The following example shows how to configure the router to send out or forward ten DNS queries from the DNS view named user3 that is associated with the VRF vpn32 before giving up:
Router(config)# ip dns view vrf vpn32 user3Router(cfg-dns-view)# domain retry 10Related Commands
show ip dns view
Displays information about a particular DNS view or about all configured DNS views, including the number of times the DNS view was used.
domain round-robin
To enable round-robin rotation of multiple IP addresses associated with a name in the hostname cache used by the DNS view, use the domain round-robin command in DNS view configuration mode. To disable round-robin functionality for the DNS view, use the no form of this command.
domain round-robin
no domain round-robin
Syntax Description
This command has no arguments or keywords.
Command Default
Round-robin rotation of multiple IP addresses associated with a name in the hostname cache is disabled for the DNS view.
Command Modes
DNS view configuration
Command History
Usage Guidelines
This command enables round-robin rotation such that each time a hostname in the internal cache is accessed, the system returns the next IP address in the cache, rotated such that the second IP address in the list becomes the first one and the first one is moved to the end of the list. For a more detailed description of round-robin functionality, see the description of the ip domain round-robin global command in the Cisco IOS IP Addressing Services Command Reference.
To display the cached list of hostnames and addresses specific to a particular DNS view or for all configured DNS views, use the show hosts command. To define static hostname-to-address mappings in the global hostname cache or VRF hostname cache for the specified DNS view, use the ip host command. To display the round-robin setting for the DNS view, use the show ip dns view command.
Examples
The following example shows how to define the hostname www.example.com with three IP addresses and then enable round-robin rotation for the default DNS view associated with the global VRF. Each time that hostname is referenced internally or queried by a DNS client sending a query to the Cisco IOS DNS server on this system, the order of the IP addresses associated with the host www.example.com will be changed. Because most client applications look only at the first IP address associated with a hostname, this results in different clients using each of the different addresses and thus distributing the load among the three different IP addresses.
Router(config)# ip host view www.example.com 192.168.2.100 192.168.2.200 192.168.2.250Router(config)# ip dns view defaultRouter(cfg-dns-view)# domain lookupRouter(cfg-dns-view)# domain round-robinRelated Commands
domain timeout
To configure the number of seconds to wait for a response to a Domain Name System (DNS) query sent or forwarded by the DNS view, use the domain timeout command in DNS view configuration mode. To remove the specification of the number of seconds for a DNS view to wait, use the no form of this command.
domain timeout seconds
no domain timeout
Syntax Description
Command Default
number: 3 seconds
Command Modes
DNS view configuration
Command History
Usage Guidelines
This command configures the number of seconds to wait for a response to a DNS query sent or forwarded by the DNS view.
To display the number of seconds configured for the DNS view, use the show ip dns view command.
Examples
The following example shows how to configure the router to wait 8 seconds for a response to a DNS query received in the DNS view named user3 that is associated with the VRF vpn32:
Router(config)# ip dns view vrf vpn32 user3Router(cfg-dns-view)# domain timeout 8Related Commands
show ip dns view
Displays information about a particular DNS view or about all configured DNS views, including the number of times the DNS view was used.
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
12.3(8)YA
This command was introduced.
12.3(14)T
This command was integrated into Cisco IOS Release 12.3(14)T.
Examples
The following example shows how to configure a list of hosts:
ip host-list testhost vrf abc 10.10.0.0Related Commands
ip host-list
Specifies a list of hosts that will receive DDNS updates of A and PTR RRs.
http (DDNS-update-method)
To specify an update method for address (A) and pointer (PTR) Resource Records (RRs) as HTTP and enter DDNS-HTTP configuration mode, use the http command in DDNS-update-method configuration mode. To disable HTTP dynamic updates, use the no form of this command.
http {add url-string | remove url-string}
no http
Syntax Description
Defaults
No HTTP update method is configured.
Command Modes
DDNS-update-method configuration
Command History
12.3(8)YA
This command was introduced.
12.3(14)T
This command was integrated into Cisco IOS Release 12.3(14)T.
Examples
The following example shows how to specify the DynDNS.org to process the updates:
ip ddns update method unit-testhttp add http://myuserid:secret@members.dyndns.org/nic/update?system=dyndns&hostname= mywebsite&myip=10.10.10.10The 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, your account username at the HTTP site should be used. Where the word "PASSWORD" appears in the URL, your 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&IPAddress=<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&username=USERNAME&password=PASSWORD&host=<h>&ip=<a>DYNS
http://USERNAME:PASSWORD@www.dyns.cx/postscript.php?username=USERNAME&password=PASSWORD&host=<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
Related Commands
internal (DDNS-update-method)
To specify an update method for Dynamic Domain Name System (DDNS) address (A) and pointer (PTR) Resource Records (RRs) as a Cisco IOS internal cache, use the internal command in DDNS-update-method configuration mode. To disable the internal dynamic updates, use the no form of this command.
internal
no internal
Syntax Description
This command has no arguments or keywords.
Defaults
No internal cache update method is configured.
Command Modes
DDNS-update-method configuration
Command History
12.3(8)YA
This command was introduced.
12.3(14)T
This command was integrated into Cisco IOS Release 12.3(14)T.
Usage Guidelines
This command is useful in conjunction with turning on the internal Cisco IOS DNS name-server. The DNS name-server is enabled by using the ip dns server command. This command enables the name-server to reply to requests for an IP address associated with the hostname that was added to the internal name cache. Not all images have Cisco IOS DNS name-server functionality, so the internal command will not be available. Refer to Feature Navigator at http://www.cisco.com/go/fn to verify the name-server functionality in your image.
When the internal type of update is specified, an entry into the Cisco IOS name cache is added, which is basically the same as entering the ip host abc.com 10.0.0.1 command. The hostname "abc" and the IP address "10.0.0.1" are associated with an interface.
Examples
The following example shows how to configure a server to send DDNS updates to the internal Cisco IOS cache:
ip ddns update method mytestinternalRelated Commands
ip ddns update method
Enables DDNS as the update method and assigns a method name.
interval maximum
To specify a maximum interval at which Dynamic Domain Name System (DDNS) updates of address (A) and pointer (PTR) Resource Records (RRs) occur, use the interval maximum command in DDNS-update-method configuration mode. To disable the interval, use the no form of this command.
interval maximum days hours minutes seconds
no interval maximum
Syntax Description
Defaults
No maximum interval is configured.
Command Modes
DDNS-update-method configuration
Command History
12.3(8)YA
This command was introduced.
12.3(14)T
This command was integrated into Cisco IOS Release 12.3(14)T.
Examples
The following example shows how to configure the update method, the maximum interval of the updates (globally), and the hostname on the interface:
interface ethernet1ip ddns update hostname abc.dyndns.orgip ddns update mytestip ddns update method mytesthttp add http://test:test@members.dyndns.org/nic/update?system=dyndns&hostname=myhost&myip=10.10.10.10interval maximum 1 0 0 0Related Commands
ip ddns update method
Enables DDNS as the update method and assigns a method name.
interval minimum
To specify a minimum interval at which Dynamic Domain Name System (DDNS) updates of address (A) and pointer (PTR) Resource Records (RRs) occur, use the interval minimum command in DDNS-update-method configuration mode. To disable the minimum interval, use the no form of this command.
interval minimum days hours minutes seconds
no interval minimum
Syntax Description
Command Default
No minimum interval is configured.
Command Modes
DDNS-update-method configuration
Usage Guidelines
DDNS updates for interfaces acquiring their address through DHCP occur every time the DHCP lease is renewed. If the lease is renewed more often than the minimum update interval needed, then a problem may occur with the updates. Sites accepting HTTP-style updates, such as DynDNS.org, may report an error if the updates occur too often. The interval minimum command forces the system to ignore updates that would occur too often.
Currently, the DynDNS.org policy is that updates can not be made more often than once every 10 minutes. This policy is subject to change in the future. The interval minimum command helps to guarantee that updates will not be sent too often.
Command History
Examples
The following example shows how to configure the minimum interval so that updates would not be sent to DynDNS.org any more often than once every 15 minutes.
ip ddns update method my testinterval minimum 0 0 15 0httpadd http://test:test@members.dyndns.org/nic/update?system=dyndns&hostname=myhostname&myip=10.10.10 .1Related Commands
ip ddns update method
Enables DDNS as the update method and assigns a method name.
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
12.3(8)YA
This command was introduced.
12.3(14)T
This command was integrated into Cisco IOS Release 12.3(14)T.
Usage Guidelines
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 hostname testhostRelated Commands
ip ddns update method
Specifies a method of DDNS updates of A and PTR RRs and the maximum interval between the updates.
ip ddns update method
To specify a method and method name for updating Dynamic Domain Name System (DDNS) address (A) and pointer (PTR) Resource Records (RRs) and enter DDNS-update-method configuration mode, use the ip ddns update method command in global configuration mode. To disable the dynamic updating, use the no form of this command.
ip ddns update method method-name
no ip ddns update method
Syntax Description
Defaults
No DDNS update method is configured.
Command Modes
Global configuration
Command History
12.3(8)YA
This command was introduced.
12.3(14)T
This command was integrated into Cisco IOS Release 12.3(14)T.
Usage Guidelines
The interface configuration overrides the global configuration.
Examples
The following example shows how to assign a DDNS update method name:
ip ddns update method unit-testOnce you have assigned the method name, you can specify the type of update (DDNS or HTTP) and set a maximum interval. Refer to the ddns and http commands for more information.
Related Commands
ddns
Specifies DDNS as the update method for A and PTR RRs.
http
Specifies HTTP as the update method for A and PTR RRs.
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 {both | none}]
no ip dhcp client update dns [server {both | none}]
Syntax Description
Defaults
No default behavior.
Command Modes
Interface configuration
Command History
12.3(8)YA
This command was introduced.
12.3(14)T
This command was integrated into Cisco IOS Release 12.3(14)T.
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.
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.
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 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 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.
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 ddns update method
Specifies a method of DDNS updates of A and PTR RRs and the maximum interval between the updates.
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 {both | none}]
no ip dhcp client update dns
Syntax Description
Defaults
No default behavior.
Command Modes
Global configuration
Command History
12.3(8)YA
This command was introduced.
12.3(14)T
This command was integrated into Cisco IOS Release 12.3(14)T.
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.
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 instruct 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.
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 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 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.
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 ddns update method
Specifies a method of DDNS updates of A and PTR RRs and the maximum interval between the updates.
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
12.3(8)YA
This command was introduced.
12.3(14)T
This command was integrated into Cisco IOS Release 12.3(14)T.
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 dns name-list
To add a hostname pattern-matching rule to the end of a Domain Name System (DNS) name list, use the ip dns name-list command in global configuration mode. To remove a rule from a DNS name list or to remove an entire name-list, use the no form of this command.
ip dns name-list name-list-number {deny | permit} pattern
no ip dns name-list name-list-number [{deny | permit} pattern]
Syntax Description
Command Default
No DNS name list is defined or modified. The access list defaults to an implicit deny .* clause. The access list is always terminated by an implicit deny .* clause.
Command Modes
Global configuration
Command History
Usage Guidelines
This command adds a hostname pattern-matching rule to the end of the specified DNS name list. A DNS name list is identified by a unique name-list-number value and defines an ordered list of hostname pattern-matching rules that the Cisco IOS software can use to match hostnames in a DNS query.
If the DNS name list does not exist yet, it is automatically created.
When a DNS name list is used to determine if a DNS view list member can be used to handle an incoming DNS query, the individual deny and permit clauses function as follows:
•
•
•
For any DNS name list number, the ip dns name-list command can be entered multiple times to specify any number of pattern-matching rules in a single name list.
To display a particular DNS name list or all configured name lists, use the show ip dns name-list command.
Use of Pattern Matching Characters to Specify the Hostname Pattern
Any rule in a DNS name list can include Cisco regular expression pattern-matching characters in the regular expression that defines the hostname pattern. For a detailed description of regular expressions and regular expression pattern-matching characters, see the Cisco IOS Terminal Services Configuration Guide.
Use of a DNS Name List Definition
A DNS name list can be referenced by a DNS view list (accessed by using the ip dns view-list command), within a DNS view list member definition (accessed by using the view command) that has been configured to deny or permit the use of that DNS view for handling a given DNS query based on whether the destination hostname adheres to a particular DNS name list. To configure this type of usage restriction on the view list member, use the restrict name-group command.
Examples
The following example shows how to configure DNS name list number 9 so that the name list will be matched if the query hostname matches either www.example2.com or *.example3.com:
Router(config)# ip dns name-list 9 permit www.example2.comRouter(config)# ip dns name-list 9 permit .*.example3.orgRelated Commands
ip dns primary
To configure the router as authoritative for a zone, use the ip dns primary command in global configuration mode. To configure the router as nonauthoritative for a zone, use the no form of this command.
ip dns primary domain-name soa primary-server-name mailbox-name [refresh-interval [retry-interval [expire-ttl [minimum-ttl]]]]
no ip dns primary domain-name
Syntax Description
Command Default
No authority record parameters are configured for the DNS name server, so queries to the DNS server for locally defined hosts will not receive authoritative responses from this server.
Command Modes
Global configuration
Command History
Usage Guidelines
Use this command to configure the router as an authoritative name server for the host table, or zone file, of a DNS domain. The primary name server name and a DNS mailbox name are required authority record parameters. Optionally, you can override the default values for the polling refresh interval, the refresh retry interval, the authority expire time, and the minimum TTL for zone information.
To display the authoritative name server configuration for the router, use the show ip dns primary command.
Examples
The following example shows how to configure the router as the primary DNS server authoritative for the example.com domain, or zone:
Router(config)# ip dns primary example.com soa ns1.example.com mb1.example.com 10800 900 5184000 172800In the above example, the DNS domain name of the router is ns1.example.com, and the administrative contact for this zone is mb1@example.com. The refresh time is 3 hours, the refresh retry time is 15 minutes, the authority expire time is 60 days, and the minimum TTL is 2 days.
Related Commands
ip dns server queue limit
To configure a limit to the size of the queues used by the Domain Name System (DNS) server processes, use the ip dns server queue limit command in global configuration mode. To remove any limit on the queue, use the no form of this command.
ip dns server queue limit forwarder queue-size-limit
no ip dns server queue limit forwarder
Syntax Description
forwarder
Sets the queue limit for the forwarder queue.
queue-size-limit
Specifies the maximum size to be used for the queue. Valid range is from 0 to 1000000. Value 0 indicates no limit.
Command Default
The queue limit is set to 0, indicating there is no limit on the queue.
Command Modes
Global configuration (config)
Command History
12.4(20)T
This command was introduced.
12.4(24)T
The director keyword was removed.
Usage Guidelines
When a DNS query is forwarded to another nameserver for resolution, some memory space is held for the corresponding DNS query until an appropriate response is received or until there is a timeout. If the queries are being received at a very high rate, this may result in the free I/O memory getting exhausted.
Use the ip dns server queue limit command to set a limit to the size of the queue.
Examples
The following example shows how to set the limit to the forwarder queue used by the DNS server:
Router(config)# ip dns server queue limit forwarder 10Router(config)#Related Commands
ip dns server view-group
To specify the default Domain Name System (DNS) server view list for the router, use the ip dns server view-group command in global configuration mode. To remove this definition, use the no form of this command.
ip dns server view-group view-list-name
no ip dns server view-group
Syntax Description
Command Default
No default DNS view list is configured; incoming queries arriving on an interface not assigned a specific DNS view list will be handled using the global default view.
Command Modes
Global configuration
Command History
Usage Guidelines
This command configures the router to use the specified DNS server view list as the default DNS view list. The default DNS view list is used to determine which DNS view the router will use to handle a given incoming DNS query that arrives on an interface that is not configured with a DNS view list. The router checks these types of DNS queries against the DNS view list entries (in the order specified in the DNS view list) and uses the first DNS view list member whose restrictions allow the view to handle that query.
To specify that the router uses a particular DNS view list to choose the DNS view to use to handle incoming DNS queries that arrives on a specific interface, use the ip dns view-group command.
Note
Examples
The following example shows how to configure the DNS name list userlist1 as the default name list:
Router(config)# ip dns server view-group userlist1Related Commands
