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 >
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