HP 6125XLG R2306-HP 6125XLG Blade Switch Layer 3 - IP Services Configuration G - Page 85

Configuring DNS Overview Domain Name System (DNS) is a distributed database used by TCP/IP applications to translate domain names into IP addresses. With DNS, you can use easy-to-remember domain names in some applications and let the DNS server translate them into correct IP addresses. The domain name-to-IP address mapping is called a DNS entry. DNS services can be static or dynamic. After a user specifies a name, the device checks the local static name resolution table for an IP address. If no IP address is available, it contacts the DNS server for dynamic name resolution, which takes more time than static name resolution. To improve efficiency, you can put frequently queried name-to-IP address mappings in the local static name resolution table. Static domain name resolution Static domain name resolution means setting up mappings between domain names and IP addresses. You can find IP addresses of the corresponding domain names in the static domain resolution table when you use applications such as Telnet. Dynamic domain name resolution Resolution process 1. A user program sends a name query to the resolver of the DNS client. 2. The DNS resolver looks up the local domain name cache for a match. If the resolver finds a match, it sends the corresponding IP address back. If not, it sends a query to the DNS server. 3. The DNS server looks up the corresponding IP address of the domain name in its DNS database. If no match is found, the server sends a query to other DNS servers. This process continues until a result, whether successful or not, is returned. 4. After receiving a response from the DNS server, the DNS client returns the resolution result to the user program. Figure 30 Dynamic domain name resolution Request User program Response Resolver Read Save Request Response DNS server Cache DNS client 76