Computer Proficiency Practice Test

The function of a DNS cache on a client is to store recent domain-name to IP-address mappings locally so lookups can be resolved quickly without repeatedly contacting a DNS server. When you visit a site, your device resolves the domain to an IP address; if that address is already in the cache and still valid (not expired by its TTL), the system can use it right away, which speeds up the connection and reduces network traffic. Each cached entry has a time-to-live, after which it expires and must be looked up again to ensure the address is still correct. The cache may also store negative results (domains that don’t exist) to avoid repeated failed lookups, which is another efficiency aid. This purpose is different from storing credentials, blocking untrusted domains, or directing email routing.