Q: Switching connectivity providers and root name server updates

[Barry Margolin]

In article <9o5nur$g1d at pub3.rc.vix.com>,
Chin Fang  <fangchin at Stanford.EDU> wrote:
>
>Barry,
>
>[...]
>
>After searching the archive a bit more, I ran into an article in which
>you replied another list reader for a similar situation, excerpted below:
>
>  In article <9mlrgq$4tm at pub3.rc.vix.com>, babu <babu at crestecdigital.com> wrote:
>  >We are going to replace our T1 line with another ISP's T1. So our web  
>  >servers/sites network/IP addresses will change. Is there anyway we can get
>  >our new T1 line with no down time or least down time of our web servers? 
>  >Because DNS updation takes 2,3 days , what should I do to make the servers
>  >available on the internet.
>
>  You'll have the least downtime if you can run both T1's simultaneously for
>  a short while.  Configure your servers with addresses from both ISP's
>  address blocks.  After the new line comes up, change your DNS to give the
>  new server addresses.  Once the TTLs on the old addresses runs out you can
>  shut down the old T1.
>
>In your suggestion above, by "can run both T1's simultaneously" did you mean
>
>1. running BGP on the router for a while, or 
>2. just simply leave one name server on the old T1 (with new IP info of 
>   course for zones that it is authoritative) while the rest name servers 
>   are moved to the new T1 on their new IP addresses?

#2.  BGP is needed to allow two T1's to host the same IP block, but my
point was that you want to continue responding to the *old* IP of your
nameserver while also responding to the new IP.  This doesn't require use
of BGP; you can just route the old IP down the old T1 and the new IP down
the new T1.

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