What does the DNS service do?

Discussion in 'Mac OS X Server, Xserve, and Networking' started by 9000, Nov 29, 2013.

  1. 9000 macrumors 6502

    Joined:
    Sep 29, 2013
    Location:
    Hyrule
    #1
    I see a DNS service on Snow Leopard Server running on my Mac Mini. It lets me put in forwarding addresses that it'll use if it gets a DNS lookup it cannot handle itself. And I'm using it for domain name lookups (that is, if I visit macrumors.com, my computer asks the DNS for its IP address). But I don't understand what the service does exactly.

    Now, the question is: When it gets requests that it must ask another server for, does it then cache these in some semi-permanent cache that it'll use in the future? My goal is to get a speedy local DNS that usually won't rely on outside servers.
     
  2. mackpro macrumors member

    mackpro

    Joined:
    Feb 1, 2008
    Location:
    Indiana University
    #2
    Great question! Bump!
     
  3. Peace macrumors Core

    Peace

    Joined:
    Apr 1, 2005
    Location:
    Space--The ONLY Frontier
    #3
    You guys answered your own question. A DNS translates a name into an IP. It stores IP's associated with a name and when you type in the name it takes you to the name.

    This is why some people flush out the DNS on occasion because the name may be associated with a different IP number.

    Yes. A DNS server does have a cache of numbers associated with a name.
     
  4. 9000 thread starter macrumors 6502

    Joined:
    Sep 29, 2013
    Location:
    Hyrule
    #4
    I didn't know it cached them. It could have been merely using other DNS services to handle requests, given my minimal knowledge about this. So it does cache them, you're saying. Do you know how frequently (if ever) it flushes this cache?
     
  5. chris.k macrumors member

    Joined:
    May 22, 2013
    Location:
    YSSY
    #5
    It flushes entires based on the "Time to live" directive told to it by the upstream DNS.

    Each zone (domain) operator can suggest a suitable TTL which is included in the returned record to the querying DNS. The Zone information SOA record generally holds this record, but can be overridden per A/PTR/NS/MX etc.....

    Downstream DNSs are supposed to honour this value, and flush their cache for this zone when it expires.
     

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