Is it safe to use another DNS server?

How would you instruct a Linux system to use the local networks dns cache located at 192.168.1.254 or the isps dns cache located on 1.2.3.4 if the lan name server is unavailable?

• Answer:

  If your linux box acquire address automatically from your router then your computer already is using dns cache located at your router. Router is in almost all cases already using ISP DNS. If you use static IP and some different DNS and you want to change it back to 192.168.1.254 you can use it probably through Network Manager. Most linux distribution has one. Example for Ubuntu Click System menu, click Preferences, then click Network Connections. Select the connection for which you want to configure local DNS. For example: To change the settings for an Ethernet connection, select the Wired tab, then select your network interface in the list. It is usually called eth0. To change the settings for a wireless connection, select the Wireless tab, then select the appropriate wireless network. Click Edit, and in the window that appears, select the IPv4 Settings or IPv6 Settings tab. If the selected method is Automatic (DHCP), open the dropdown and select Automatic (DHCP) addresses only instead. If the method is set to something else, do not change it. In the DNS servers field, enter the local DNS IP addresses, separated by a space: 192.168.1.254 Click Apply to save the changes. If you are prompted for a password or confirmation, type the password or provide confirmation. Test that your setup is working correctly; Repeat the procedure for additional network connections you want to change.