Can you tell a Cisco router NOT to cache a DNS lookup?

Discussion in 'Cisco' started by Terra Dactyl, Jan 5, 2005.

  1. Terra Dactyl

    Terra Dactyl Guest

    Normally when a Cisco router performs a DNS lookup to a domain name
    server it caches the lookup in the router's memory for some
    undetermined peroid of time.

    For instance;

    Test-box>ping www.cisco.com

    Is it possible to tell the router not to cache DNS lookups, so that
    it will have to query the DNS server everytime it needs a domain to IP
    address mapping?
    I do have a legitimate reason for wanting the router not to cache a
    DNS entry although I have not posted it here.

    Thanks
     
    Terra Dactyl, Jan 5, 2005
    #1
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  2. Terra Dactyl

    rave Guest

    The solution is setting the ttl to 0 on DNS server.
    Router caches the DNS reply, and ages it out upon ttl expired.
     
    rave, Jan 6, 2005
    #2
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  3. Some versions of BIND don't handle TTL 0 very well. I recommend using 1
    instead. It will be cached, but so briefly that it's not likely to be a
    problem.
     
    Barry Margolin, Jan 6, 2005
    #3
  4. ~ In article <>,
    ~
    ~ > The solution is setting the ttl to 0 on DNS server.
    ~ > Router caches the DNS reply, and ages it out upon ttl expired.
    ~
    ~ Some versions of BIND don't handle TTL 0 very well. I recommend using 1
    ~ instead. It will be cached, but so briefly that it's not likely to be a
    ~ problem.

    It is doubtful however that the OP will be able to prevail
    upon the manager of the cisco.com zone to change the TTL
    field on the www.cisco.com A RR.

    A more practical approach in his case would be to do a
    "clear host <hostname>" prior to his ping. In recent IOS,
    you could write a Tcl script to simply the operation.

    Aaron
     
    Aaron Leonard, Jan 6, 2005
    #4
  5. Terra Dactyl

    Hansang Bae Guest

    [snip]
    [snip]

    How funny. I just figured out what "OP" means. There was a poster a
    while back with that nickname and I just got used to thinking "Op" and
    not "OP"



    hsb


    "Somehow I imagined this experience would be more rewarding" Calvin
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    Hansang Bae, Jan 7, 2005
    #5
  6. Terra Dactyl

    BB Guest

    Try no ip domain-lookup

     
    BB, Jan 7, 2005
    #6
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