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