Dial-on-Demand
A more sophisticated dial-up solution is dial-on-demand. Dial-on-demand Internet connections often use dedicated hardware, such as a small dial-up router, to provide connectivity whenever it’s needed. If you initiate a connection to the Internet from the “remote” end of a dial-on-demand router, it dials up another router on the Internet and routes your packets across. If the connection is idle for more than a specified amount of time, the router drops the connection.
The challenge with DNS is to keep a local name server from continuously bringing the dial-on-demand connection up and down like a yo-yo. This could be costly, because you sometimes pay a premium for connection setup with technologies such as ISDN.
The most important strategy for minimizing this off-net traffic is to configure your resolvers to use a minimal search list (or DNS suffix list, as it’s called in Windows). The default Windows search list (which you get when you don’t specify an explicit list of DNS suffixes to search) searches the ancestors of your local domain, which can cause unnecessary remote traffic. For instance, say your local domain is tinyoffice.majorcorp.com, and you have a dial-on-demand connection to Majorcorp’s enterprise network. On hosts without an explicit DNS suffix list, your default search list includes:
tinyoffice.majorcorp.com majorcorp.com
A user typing telnet foo.tinyoffice.majorcorp.com to log into the workstation next to him might inadvertently cause lookups of both of ...
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