HP 6125G HP 6125G & 6125G/XG Blade Switches Layer 3 - IP Services Conf - Page 69

Configuring IPv4 DNS, Overview, Static domain name resolution, Dynamic domain name resolution

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Configuring IPv4 DNS Overview Domain Name System (DNS) is a distributed database used by TCP/IP applications to translate domain names into corresponding 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. 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. IP addresses of the corresponding domain names can be found in the static domain resolution table when you use applications such as Telnet. Dynamic domain name resolution 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 a higher level DNS server. 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 application. Figure 35 Dynamic domain name resolution User Request program Response Resolver Read Save Request Response DNS server Cache DNS client Figure 35 shows the relationship between the user program, DNS client, and DNS server. The DNS client is made up of the resolver and cache. The user program and DNS client can run on the same device or different devices, but the DNS server and the DNS client usually run on different devices. 61

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61
Configuring IPv4 DNS
Overview
Domain Name System (DNS) is a distributed database used by TCP/IP applications to translate domain
names into corresponding 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.
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. IP
addresses of the corresponding domain names can be found in the static domain resolution table when
you use applications such as Telnet.
Dynamic domain name resolution
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 a higher level DNS server. 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
application.
Figure 35
Dynamic domain name resolution
Figure 35
shows the relationship between the user program, DNS client, and DNS server.
The DNS client is made up of the resolver and cache. The user program and DNS client can run on the
same device or different devices, but the DNS server and the DNS client usually run on different devices.
Request
Response
Response
Request
Save
Read
DNS client
DNS server
Resolver
Cache
User
program