Ah, many thanks ! :) On Fri, Sep 18, 2015 at 3:37 PM, John Miller <johnm...@brandeis.edu> wrote:
> The .com nameservers don't know anything about ftp.example.com; they > just know the nameservers for example.com. So have no fear -- BIND > will not cache an upstream response for ftp.example.com: you'll only > hear about ftp.example.com from the example.com nameservers. > > Pretty much all upstream nameservers: root NSs, .com NSs, example.com > NSs--are authoritative-only. They don't cache or offer cached > responses. (Not 100% accurate, but nearly always so.) > > John > > On Fri, Sep 18, 2015 at 2:58 PM, Danny Sinang <d.sin...@gmail.com> wrote: > > As a follow-up to your answer for question #2, after my clearing the > cache > > or restarting BIND, won't BIND find an old cache of "ftp.example.com" > in the > > ".com" top level DNS server ? > > > > Regards, > > Danny > > > > On Fri, Sep 18, 2015 at 2:51 PM, John Miller <johnm...@brandeis.edu> > wrote: > >> > >> On Fri, Sep 18, 2015 at 2:35 PM, Danny Sinang <d.sin...@gmail.com> > wrote: > >> > Hi, > >> > > >> > Our vendor is changing their FTP server's IP address tomorrow. > >> > > >> > 1. How can I tell how long their DNS change will propagate to us ? > >> > >> Whatever TTL you have cached when the vendor makes the switch is how > >> long it'll take for your caching servers to pick up the change. > >> > >> > a. Do I just run dig a "ftp.example.com" and look for the TTL > for > >> > that > >> > DNS entry ? > >> > b. Every time I run that command, the TTL is shrinking. How do I > >> > find > >> > out the full TTL for it ? > >> > >> If you want to know the full TTL, ask the company's NSs directly - > >> authoritative servers only give out the full TTL. > >> > >> > 2. Can I just restart BIND tomorrow to clear its cache and force it to > >> > query > >> > the "example.com" name server for "ftp.example.com" (so as not to > wait > >> > for > >> > the propagation to reach us) ? > >> > >> Sure can. Depending on your BIND version, you can also run rndc > >> flushname <name> and it'll clear just that name from your cache. > >> > >> If the TTL is very long, don't forget about client-side caching as > >> well. Windows and OS X cache DNS lookups by default. > >> > >> John > >> _______________________________________________ > >> Please visit https://lists.isc.org/mailman/listinfo/bind-users to > >> unsubscribe from this list > >> > >> bind-users mailing list > >> bind-users@lists.isc.org > >> https://lists.isc.org/mailman/listinfo/bind-users > > > > > > > > -- > John Miller > Systems Engineer > Brandeis University > johnm...@brandeis.edu > (781) 736-4619 > _______________________________________________ > Please visit https://lists.isc.org/mailman/listinfo/bind-users to > unsubscribe from this list > > bind-users mailing list > bind-users@lists.isc.org > https://lists.isc.org/mailman/listinfo/bind-users >
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