The default gateway and DNS server can be different IP addresses. Assume that the TCP/IP adapter of a PC is configured with an IP address of 192.168.1.1, which is the LAN interface of the router which is connected to the internet. The ISP has provided a DNS IP address which is a Public IP address. Before providing any IP address for the DNS Server on the TCP/IP adapter setting of the PC, the user can check the reachability of the public IP address of the DNS server using the ping command. If it is reachable, then the user can configure the Public IP address of the DNS server as the DNS server IP address on the PC.