The Dns-Server [Ip Address] Cisco command

The 'dns-server [ip address]' command is used to configure a primary or secondary Domain Name System (DNS) server address in Cisco devices. This command is applied to enable the resolution of domain names to IP addresses, allowing devices to communicate across networks and access various online services.

Syntax:

dns-server [ip-address]

Parameters:

• ip-address: The IP address of the primary or secondary DNS server to be configured.

Usage: To configure a primary or secondary DNS server, use the following steps:

1. Enter the configuration mode on the Cisco device by using the 'configure terminal' command.
2. Specify the type of DNS server you want to configure using the 'dns-server' command.
3. Provide the IP address of the DNS server using the '[ip-address]' parameter.
4. Repeat step 3 to add additional DNS servers if desired.
5. Save the configuration by entering the 'end' command.

Functionality: The 'dns-server [ip address]' command configures the device to use the specified IP address for DNS resolution. When a device sends a request to resolve a domain name, the device will query the configured DNS server to obtain the corresponding IP address. If the DNS server is unavailable or does not have the necessary information, the device will continue querying other configured DNS servers or forward the request to an upstream DNS server.

Applicable Devices: The 'dns-server [ip address]' command is commonly used on a variety of Cisco devices, including:

• Routers
• Switches
• Firewalls
• Wireless Access Points
• Network Modules

Benefits: Configuring DNS servers allows devices to efficiently resolve domain names, enabling access to online resources and services. It also helps ensure that devices can communicate properly with other devices on the network. Additionally, having multiple DNS servers configured provides redundancy and improves overall network resilience.

dns-server [ip address] Usage Examples

The Cisco command dns-server [ip address] is used to specify a DNS server for a specific interface on a Cisco router or switch. Here are some examples:

Configuring a single DNS server for an interface:

interface GigabitEthernet0/1
 dns-server 192.168.1.1

This command sets the DNS server for interface GigabitEthernet0/1 to 192.168.1.1.

Configuring multiple DNS servers for an interface:

interface GigabitEthernet0/1
 dns-server 192.168.1.1
 dns-server 192.168.1.2

This command sets the DNS servers for interface GigabitEthernet0/1 to 192.168.1.1 and 192.168.1.2. In case the primary DNS server becomes unavailable, the router will automatically use the secondary DNS server.

Configuring DNS servers for an interface using a domain name:

interface GigabitEthernet0/1
 dns-server example.com

This command sets the DNS server for interface GigabitEthernet0/1 to the IP address associated with the domain name example.com. The router will resolve the domain name to an IP address using a DNS server configured on the router or through DHCP.

Configuring DNS servers for an interface using an IPv6 address:

interface GigabitEthernet0/1
 dns-server 2001:db8:85a3:08d3:1319:8a2e:0370:7334

This command sets the DNS server for interface GigabitEthernet0/1 to the IPv6 address 2001:db8:85a3:08d3:1319:8a2e:0370:7334.

Configuring DNS servers for an interface using the default DNS server:

interface GigabitEthernet0/1
 dns-server default

This command sets the DNS server for interface GigabitEthernet0/1 to the default DNS server configured on the router. The default DNS server is typically configured using the ip domain-lookup command.

Removing DNS server configuration for an interface:

interface GigabitEthernet0/1
no dns-server

This command removes the DNS server configuration for interface GigabitEthernet0/1.