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This chapter describes how to configure the Domain Name Server (DNS) client on the Cisco NX-OS device.
This chapter includes the following sections:
This section includes the following topics:
If your network devices require connectivity with devices in networks for which you do not control the name assignment, you can assign device names that uniquely identify your devices within the entire internetwork using the domain name server (DNS). DNS uses a hierarchical scheme for establishing host names for network nodes, which allows local control of the segments of the network through a client-server scheme. The DNS system can locate a network device by translating the hostname of the device into its associated IP address.
On the Internet, a domain is a portion of the naming hierarchy tree that refers to general groupings of networks based on the organization type or geography. Domain names are pieced together with periods (.) as the delimiting characters. For example, Cisco is a commercial organization that the Internet identifies by a com domain, so its domain name is cisco.com. A specific hostname in this domain, the File Transfer Protocol (FTP) system, for example, is identified as ftp.cisco.com.
Name servers keep track of domain names and know the parts of the domain tree for which they have complete information. A name server may also store information about other parts of the domain tree. To map domain names to IP addresses in Cisco NX-OS, you must identify the hostnames, specify a name server, and enable the DNS service.
Cisco NX-OS allows you to statically map IP addresses to domain names. You can also configure Cisco NX-OS to use one or more domain name servers to find an IP address for a host name.
A name server handles client-issued queries to the DNS server for locally defined hosts within a particular zone as follows:
Name servers answer DNS queries (forward incoming DNS queries or resolve internally generated DNS queries) according to the forwarding and lookup parameters configured for the specific domain.
Cisco NX-OS supports stateless restarts for the DNS client. After a reboot or supervisor switchover, Cisco NX-OS applies the running configuration.
Cisco NX-OS supports multiple instances of the DNS clients that run on the same system. You can configure a DNS client in each virtual device connect (VDC).You can optionally have a different DNS client configuration in each virtual routing and forwarding (VRF) instance within a VDC. By default, Cisco NX-OS places you in the default VDC and default VRF unless you specifically configure another VDC and VRF. See the Cisco NX-OS Virtual Device Context Configuration Guide and Chapter14, “Configuring Layer 3 Virtualization”
The following table shows the licensing requirements for this feature:
The DNS client has the following configuration guidelines and limitations:
Table 4-1 lists the default settings for DNS client parameters.
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This section includes the following topics:
Note If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature might differ from the Cisco IOS commands that you would use.
You can configure the DNS client to use a DNS server on your network.
Ensure that you have a domain name server on your network.
Ensure that you are in the correct VDC (or use the switchto vdc command).
2. ip host name address1 [ address2... address6 ]
3. (Optional) ip domain-name name [ use-vrf vrf-name ]
4. (Optional) ip domain-list name [ use-vrf vrf-name ]
5. (Optional) ip name-server address1 [ address2... address6 ] [ use-vrf vrf-name ]
This example shows how to configure a default domain name and enable DNS lookup:
switch(config)# ip domain-name cisco.com 192.0.2.1 use-vrf management
switch(config)# ip domain-lookup
switch(config)# copy running-config startup-config
You can configure a DNS client within a VRF. If you do not enter VRF configuration mode, your DNS client configuration applies to the default VRF.
You can optionally configure a DNS client to use a specified VRF other than the VRF under which you configured the DNS client as a backup VRF. For example, you can configure a DNS client in the Red VRF but use the Blue VRF to communicate with the DNS server if the server cannot be reached through the Red VRF.
Ensure that you have a domain name server on your network.
Ensure that you are in the correct VDC (or use the switchto vdc command).
3. (Optional) ip domain-name name [ use-vrf vrf-name ]
4. (Optional) ip domain-list name [ use-vrf vrf-name ]
5. (Optional) ip name-server server-address1 [ server-address2... server-address6 ] [ use-vrf vrf-name ]
This example shows how to configure a default domain name and enable DNS lookup within a VRF:
switch(config)# vrf context Red
switch(config-vrf)# ip domain-name cisco.com 192.0.2.1 use-vrf management
switch(config-vrf)# copy running-config startup-config
To display the DNS client configuration, perform one of the following tasks:
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This example shows how to establish a domain list with several alternate domain names:
This example shows how to configure the hostname-to-address mapping process and specify IP DNS-based translation. The example also configures the addresses of the name servers and the default domain name.
For additional information related to implementing DNS Client, see the following sections:
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Cisco Nexus 7000 Series NX-OS Unicast Routing Command Reference, Release 5.x |
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Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 5.x |
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No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature. |
Table 4-2 lists the release history for this feature.
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