Name Servers; Dns Operation; High Availability; Virtualization Support - Cisco Nexus 7000 Series Configuration Manual

Licensing Requirements for DNS Clients

S e n d d o c u m e n t c o m m e n t s t o n e x u s 7 k - d o c f e e d b a c k @ c i s c o . c o m .
On the Internet, a domain is a portion of the naming hierarchy tree that refers to general groupings of
networks based on 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 host name in this domain, the File Transfer
Protocol (FTP) system, for example, is identified as ftp.cisco.com.

Name Servers

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 first identify the host names, then
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.

DNS Operation

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.

High Availability

Cisco NX-OS supports stateless restarts for the DNS client. After a reboot or supervisor switchover,
Cisco NX-OS applies the running configuration.

Virtualization Support

Cisco NX-OS supports multiple instances of the DNS clients that run on the same system. You can
configure a DNS client in each VDC.You can optionally have a different DNS client configuration in
each VRF 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
Licensing Requirements for DNS Clients
The following table shows the licensing requirements for this feature:
Cisco Nexus 7000 Series NX-OS Unicast Routing Configuration Guide, Release 4.x
4-2
An authoritative name server responds to DNS user queries for a domain name that is under its zone
of authority by using the permanent and cached entries in its own host table. If the query is for a
domain name that is under its zone of authority but for which it does not have any configuration
information, the authoritative name server simply replies that no such information exists.
A name server that is not configured as the authoritative name server responds to DNS user queries
by using information that it has cached from previously received query responses. If no router is
configured as the authoritative name server for a zone, queries to the DNS server for locally defined
hosts will receive nonauthoritative responses.
Chapter 14, "Configuring Layer 3 Virtualization."
Chapter 4 Configuring DNS
OL-20002-02