- Preface
- New and Changed Information for this Release
- Overview
- Configuring Switch Profiles
- Configuring Module Pre-Provisioning
- Using Cisco Fabric Services
- Configuring User Accounts and RBAC
- Configuring Session Manager
- Configuring Online Diagnostics
- Configuring System Message Logging
- Configuring Smart Call Home
- Configuring Rollback
- Configuring DNS
- Configuring SNMP
- Configuring RMON
- Configuring SPAN
- Configuring NTP
- Index
Configuring DNS
This chapter contains the following sections:
- Information About DNS Client
- Prerequisites for DNS Clients
- Licensing Requirements for DNS Clients
- Default Settings for DNS Clients
- Configuring DNS Clients
Information About DNS Client
If your network devices require connectivity with devices in networks for which you do not control 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 hostnames 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
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 hostnames, 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 hostname.
DNS Operation
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 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 receive nonauthoritative responses.
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.
Prerequisites for DNS Clients
The DNS client has the following prerequisites:
Licensing Requirements for DNS Clients
The following table shows the licensing requirements for this feature:
Product | Licence Rquirement |
---|---|
Cicco NX-OS | DNS requires no license. Any feature not included in a license package is bundled with the Cisco NX-OS system images and is provided at no extra charge to you. For a complete explanation of the Cisco NX-OS licensing scheme, see the Cisco NX-OS Licensing Guide. |
Default Settings for DNS Clients
The following table shows the default settings for DNS client parameters.
Parameter | Default |
---|---|
DNS client | Enabled |
Configuring DNS Clients
You can configure the DNS client to use a DNS server on your network.
1. switch# configuration terminal
2. switch(config)# vrf context managment
3. switch(config)# ip host name address1 [address2... address6]
4. (Optional) switch(config)# ip domain name name [use-vrf vrf-name]
5. (Optional) switch(config)# ip domain-list name [use-vrf vrf-name]
6. (Optional) switch(config)# ip name-server server-address1 [server-address2... server-address6] [use-vrf vrf-name]
7. (Optional) switch(config)# ip domain-lookup
8. (Optional) switch(config)# show hosts
9. switch(config)# exit
10. (Optional) switch# copy running-config startup-config
DETAILED STEPS
The following example shows how to configure a default domain name and enable DNS lookup:
switch# config t switch(config)# vrf context management switch(config)# ip domain-name mycompany.com switch(config)# ip name-server 172.68.0.10 switch(config)# ip domain-lookup