Configuring Hostname Lookups

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Each host on a TCP/IP network has a designated IP address, and TCP/IP traffic is routed to hosts by address. TCP/IP requires a mechanism for clients to translate hostnames to their numeric addresses. Each client host can store the hostname/address associations in a file called hosts. You can alternately store this information on a central server, and the clients then retrieve the information on demand using a protocol called DNS. The client requests that the DNS server resolve a hostname, and the server returns the IP address. Then the client can use the IP address to communicate directly with the intended destination. In this configuration, the client must keep only one IP address locally: that of the DNS server host.

Depending on the load on the network and the DNS server itself, hostname resolution can take several seconds. This translates directly into delays when making a network connection. This is related to the message you might see in a web browser, “Looking up host name…” followed by, “Connecting to host name…”. This indicates the delay while querying a DNS server to resolve a hostname.

You can speed up hostname resolution by adding the hostname/address mapping of the database server to the hosts file on the client computer. The client can resolve the hostname to its address much faster and more reliably by looking it up in a local file than by querying a service running on another host over the network. This reduces the hostname resolution delay when initiating connections to hosts listed in the local hosts file.

Note: If you use this technique and later change the address of your database server, you must manually update the hosts files on each client workstation. Depending on the number of workstations in your enterprise, this can be tedious and time consuming. That is why DNS was invented, to centralize TCP/IP address administration. The suggestion to keep the database server address in a local file is intended to provide improved connection performance, but you should be aware of the administrative workload that it requires.
Tip: If you object to the general IP address administration tasks required by using TCP/IP (independently from the DNS issue), consider using DHCP to simplify the task of assigning and tracking IP addresses of each host on the network. InterBase works in a DHCP environment as long as the client host has some means to resolve the IP address of the server correctly at the time a client application requests an InterBase connection.