DNS cache problem

[Mike Weller]

Hi,

Our company is currently in the process of changing ISPs.  I gave the
new provider my DNS zone file with the current IP# settings, and
instructed them to set the "minimum TTL" to 10-15 minutes.  This way,
the transition would be smooth for when we switch over the actual
IP#s.

Well, after I changed the DNS authority for our domain (zyvex.com) at
networksolutions to the new ISP, I noticed that the new ISPs SOA
record was corrupt! (this was last Friday night).

> set type=SOA
> zyvex.com
Server:  dfwns1.airband.net
Address:  206.50.26.195
*** dfwns1.airband.net can't find zyvex.com: Non-existent host/domain

Yet, the A, MX and NS records were intact:
> set type=NS
> zyvex.com
Server:  dfwns1.airband.net
Address:  206.50.26.195
<snip>
Authoritative answers can be found from:
dfwns1.airband.net      internet address = 206.50.26.195
dfwns2.airband.net      internet address = 206.50.26.196

> set type=MX
> zyvex.com
<snip>
zyvex.com       preference = 10, mail exchanger = mail.zyvex.com

12 hours later (after trying to desperately get a hold of them), 
they fixed the problem, and set the TTL to 1 hour (this was
Saturday at about noon).

> set type=SOA
> zyvex.com
Server:  gordon.chem.wayne.edu
Address:  141.217.26.2

Non-authoritative answer:
zyvex.com
        origin = dfwns1.airband.net
        mail addr = hostmaster.airband.net
        serial = 2001120101
        refresh = 3600 (1H)
        retry   = 900 (15M)
        expire  = 3600000 (3600000)
        minimum ttl = 3600 (1H)

Authoritative answers can be found from:
zyvex.com       nameserver = dfwns1.airband.net
zyvex.com       nameserver = DFWNS2.airband.net
dfwns1.airband.net      internet address = 206.50.26.195
DFWNS2.airband.net      internet address = 206.50.26.196


Now here's my problem.  As a test, I asked them to change 1
unimportant hostname's IP in their DNS table.  I verified
that the hostname changed on their DNS server (dfwns1.airband.net):

Server:  dfwns1.airband.net
Address:  206.50.26.195
Name:    zyric.zyvex.com
Address:  216.138.97.43

Before the change, I polled a dozen nameservers around the world
for zyric.zyvex.com:
nslookup zyric.zyvex.com  140.221.9.6
nslookup zyric.zyvex.com 141.217.90.3
nslookup zyric.zyvex.com 141.217.1.13
nslookup zyric.zyvex.com 141.217.1.15
nslookup zyric.zyvex.com 206.191.74.19
nslookup zyric.zyvex.com 24.226.1.11

The change was made at 12pm cst today (Monday).
3 hours later, all nameservers still report the old IP
(64.241.222.34), despite the minimum TTL of 1 hour.

My question to you DNS experts is, if an SOA record is corrupt (and
thus, can't read the cache time) how long does the nameserver cache
IPs for?  Is there a way to poll "bind" to determine what the 
cache times are for any particular IP or domain?

I hope it's not too long, because our current ISP is about to drop
our service!

Thanks for any help you can provide.

-Mike

-- 
Michael J. Weller, M.Sc.               office: (972) 235-7881 x.242
weller at zyvex.com                         cell: (214) 616-6340
Zyvex Corp., 1321 N Plano           facsimile: (972) 235-7882    
Richardson, TX 75081                      icq: 6180540