Q: Switching connectivity providers and root name server updates

[Barry Margolin]

In article <9o5auu$dj9 at pub3.rc.vix.com>,
Chin Fang  <fangchin at Stanford.EDU> wrote:
>We believe the lowered TTL should help in this regard, but if a lot
>root servers do not timely (say within a hour or two) pick up the new
>IP addresses of our name servers, our site will remain invisible to
>many folks for quite a while.  This is the potential problem that we
>don't know how to deal with yet.

Even when the GTLD servers pick up the A record change, you still have the
problem that the TTL on those glue records is 2 days.  So does it really
make a big difference whether they pick up the change from NSI in 1 hour or
6 hours?  That changes the actual worst-case timeout from 49 hours to 54
hours?

What you should depend on is your off-site slave servers, whose addresses
won't change when you switch providers.  If your ISP is operating the slave
servers, you should arrange for both the old and new ISPs to do slave DNS
in parallel, and have them point to both the old and new address of the
master server (BIND allows you to put multiple addresses in the "masters"
clause).  After you switch providers, the old ISP should pick up your
changes, and everyone who still has their nameservers in their cache will
get your new addresses.  Once the caches time out, everyone will start
querying your new server or your new ISP's servers, and you can have the
old provider remove the zone from their configuration.

-- 
Barry Margolin, barmar at genuity.net
Genuity, Woburn, MA
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