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How to clean up routing cache? - Sun Solaris

Hello! My OS is the Solaris 8 When I ping some host that is not alive, first time I get error message after quite long timeout ~15...20 sec... Second time I do it I get error message almost immediately that means the error response is stored somewhere on my computer... If I wait quite long period of time I see that error message again appears after long timeout, that indicates that cache was cleand up... Question: how do I change cache time and where? How can I clean up cache myself? I looked in zillion places and commands and could ...

  1. #1

    Default How to clean up routing cache?

    Hello!

    My OS is the Solaris 8

    When I ping some host that is not alive, first time I get error
    message after quite long timeout ~15...20 sec...

    Second time I do it I get error message almost immediately that means
    the error response is stored somewhere on my computer...

    If I wait quite long period of time I see that error message again
    appears after long timeout, that indicates that cache was cleand up...

    Question: how do I change cache time and where? How can I clean up
    cache myself?

    I looked in zillion places and commands and could not find the option
    to do that...

    Thanks,
    Alexandre
    Alexandre Guest

  2. #2

    Default Re: How to clean up routing cache?

    Alexandre Patchine <com> wrote: 
     
     

    What error?
     

    What error?

    --
    Darren Dunham com
    Unix System Administrator Taos - The SysAdmin Company
    Got some Dr Pepper? San Francisco, CA bay area
    < This line left intentionally blank to confuse you. >
    Darren Guest

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  7. #7

    Default Re: How to clean up routing cache?

    Alexandre Patchine wrote:
     

    There is any such thing as an exact time. It will vary depending on
    what TTL values the DNS records are given when they are created. This
    can be different for each record. Here is some text from the
    BIND Administrator Reference Manual:

    The TTL is assigned by the administrator for the zone where
    the data originates. While short TTLs can be used to minimize
    caching, and a zero TTL prohibits caching, the realities of
    Internet performance suggest that these times should be on
    the order of days for the typical host. If a change can be
    anticipated, the TTL can be reduced prior to the change to
    minimize inconsistency during the change, and then increased
    back to its former value following the change.

    In other words, the TTL is up to the DNS administrator's discretion.

    Also keep in mind that the TTL is only a maximum. A DNS server
    that caches data from other DNS servers may choose to cache things
    for a shorter amount of time.
     

    Well, the first suggestion is that you can use some program like
    "nslookup" or "dig". They both form DNS queries directly and
    bypass the process that the system uses to resolve names. They
    will therefore give a more direct test.

    You could look up a non-existent hostname based on the system's
    time an its own hostname, for example:

    now () { nawk 'END {print srand}' /dev/null ; }
    before=`now`
    nslookup `hostname`-`now`.mydomain.com
    after=`now`
    echo "DNS resolution took `expr $after - $before` seconds"

    The second suggestion I have is that you need to define what
    you mean "slow DNS response". If you are trying to look up a
    hostname across the ocean, and the path between your DNS server
    and the remote DNS server is very slow and clogged up with traffic,
    then it might take 20 seconds for a query to be finished, and this
    might be the best possible performance.

    On the other hand, if you have a DNS server on the same host
    as the one you're testing from and it has the data cached,
    the response might take much less than 0.1 seconds.

    So, what is "slow"? This is something you may have to define
    for yourself since there isn't any obvious objective definition.

    Hope that helps.

    - Logan

    Logan Guest

  8. #8

    Default Re: How to clean up routing cache?

    thanks for the help!...

    Now I have start point for my development...

    already tested script together with Patrol...

    About slow or how much slow:
    our system is load balanced WAP server (5-10 Solaris servers) and DNS is
    supposed to be within the same network segment and situated in the same
    building/area... I thinks that delay around 200-300 ms should be considered
    as very big for it and acceptable range must be no more than 20-30 ms...

    alexandre



    "Logan Shaw" <rr.com> wrote in message
    news:sdPgb.436$austin.rr.com... 
    >
    > There is any such thing as an exact time. It will vary depending on
    > what TTL values the DNS records are given when they are created. This
    > can be different for each record. Here is some text from the
    > BIND Administrator Reference Manual:
    >
    > The TTL is assigned by the administrator for the zone where
    > the data originates. While short TTLs can be used to minimize
    > caching, and a zero TTL prohibits caching, the realities of
    > Internet performance suggest that these times should be on
    > the order of days for the typical host. If a change can be
    > anticipated, the TTL can be reduced prior to the change to
    > minimize inconsistency during the change, and then increased
    > back to its former value following the change.
    >
    > In other words, the TTL is up to the DNS administrator's discretion.
    >
    > Also keep in mind that the TTL is only a maximum. A DNS server
    > that caches data from other DNS servers may choose to cache things
    > for a shorter amount of time.

    >
    > Well, the first suggestion is that you can use some program like
    > "nslookup" or "dig". They both form DNS queries directly and
    > bypass the process that the system uses to resolve names. They
    > will therefore give a more direct test.
    >
    > You could look up a non-existent hostname based on the system's
    > time an its own hostname, for example:
    >
    > now () { nawk 'END {print srand}' /dev/null ; }
    > before=`now`
    > nslookup `hostname`-`now`.mydomain.com
    > after=`now`
    > echo "DNS resolution took `expr $after - $before` seconds"
    >
    > The second suggestion I have is that you need to define what
    > you mean "slow DNS response". If you are trying to look up a
    > hostname across the ocean, and the path between your DNS server
    > and the remote DNS server is very slow and clogged up with traffic,
    > then it might take 20 seconds for a query to be finished, and this
    > might be the best possible performance.
    >
    > On the other hand, if you have a DNS server on the same host
    > as the one you're testing from and it has the data cached,
    > the response might take much less than 0.1 seconds.
    >
    > So, what is "slow"? This is something you may have to define
    > for yourself since there isn't any obvious objective definition.
    >
    > Hope that helps.
    >
    > - Logan
    >[/ref]


    john Guest

  9. #9

    Default Re: How to clean up routing cache?

    posted from another machine and signature came as john :-)
    changed it

    thanks for the help!...

    Now I have start point for my development...

    already tested script together with Patrol...

    About slow or how much slow:
    our system is load balanced WAP server (5-10 Solaris servers) and DNS is
    supposed to be within the same network segment and situated in the same
    building/area... I thinks that delay around 200-300 ms should be considered
    as very big for it and acceptable range must be within 20-30 ms...

    alexandre


    "Logan Shaw" <rr.com> wrote in message
    news:sdPgb.436$austin.rr.com... 
    >
    > There is any such thing as an exact time. It will vary depending on
    > what TTL values the DNS records are given when they are created. This
    > can be different for each record. Here is some text from the
    > BIND Administrator Reference Manual:
    >
    > The TTL is assigned by the administrator for the zone where
    > the data originates. While short TTLs can be used to minimize
    > caching, and a zero TTL prohibits caching, the realities of
    > Internet performance suggest that these times should be on
    > the order of days for the typical host. If a change can be
    > anticipated, the TTL can be reduced prior to the change to
    > minimize inconsistency during the change, and then increased
    > back to its former value following the change.
    >
    > In other words, the TTL is up to the DNS administrator's discretion.
    >
    > Also keep in mind that the TTL is only a maximum. A DNS server
    > that caches data from other DNS servers may choose to cache things
    > for a shorter amount of time.

    >
    > Well, the first suggestion is that you can use some program like
    > "nslookup" or "dig". They both form DNS queries directly and
    > bypass the process that the system uses to resolve names. They
    > will therefore give a more direct test.
    >
    > You could look up a non-existent hostname based on the system's
    > time an its own hostname, for example:
    >
    > now () { nawk 'END {print srand}' /dev/null ; }
    > before=`now`
    > nslookup `hostname`-`now`.mydomain.com
    > after=`now`
    > echo "DNS resolution took `expr $after - $before` seconds"
    >
    > The second suggestion I have is that you need to define what
    > you mean "slow DNS response". If you are trying to look up a
    > hostname across the ocean, and the path between your DNS server
    > and the remote DNS server is very slow and clogged up with traffic,
    > then it might take 20 seconds for a query to be finished, and this
    > might be the best possible performance.
    >
    > On the other hand, if you have a DNS server on the same host
    > as the one you're testing from and it has the data cached,
    > the response might take much less than 0.1 seconds.
    >
    > So, what is "slow"? This is something you may have to define
    > for yourself since there isn't any obvious objective definition.
    >
    > Hope that helps.
    >
    > - Logan
    >[/ref]


    alexandre Guest

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