Weird DNS Issue

Hi All,

Maybe someone who knows more than me can help.

My client and I used to have the same ISP.

My client's domain is registered with Network Solutions. He just moved
his name servers and email from his previous internet provider to
Yahoo. So, if I go to Network Solutions or to any other website and do
an NSLOOKUP, it shows correctly.

However, if I do an NSLOOKUP on my email server, it points to his old
internet provider. So, if I send him email, it goes to his old email
account. If anyone else sends him email, it goes to his new
account.......

I do not understand??? I am not running any nameserver on my linux
box.........

On Fri, 07 Jul 2006 15:20:06 -0700, johndo wrote:

> However, if I do an NSLOOKUP on my email server, it points to his old
> internet provider. So, if I send him email, it goes to his old email
> account. If anyone else sends him email, it goes to his new
> account.......

Your ISP's nameserver appears to still have the other party's old DNS
server in its cache. Given enough time and the TTL on that cache will
expire.

Dave Uhring wrote:
> On Fri, 07 Jul 2006 15:20:06 -0700, johndo wrote:
>
> > However, if I do an NSLOOKUP on my email server, it points to his old
> > internet provider. So, if I send him email, it goes to his old email
> > account. If anyone else sends him email, it goes to his new
> > account.......
>
> Your ISP's nameserver appears to still have the other party's old DNS
> server in its cache. Given enough time and the TTL on that cache will
> expire.

I thought these things took like 2 or 3 days, at the most......

On Fri, 07 Jul 2006 16:30:13 -0700, johndo wrote:

>
> Dave Uhring wrote:

>> Your ISP's nameserver appears to still have the other party's old DNS
>> server in its cache. Given enough time and the TTL on that cache will
>> expire.
>
> I thought these things took like 2 or 3 days, at the most......

Depends on how the SOA records were set up on his original DNS server. I
had an ongoing problem with one ISP who had set his TTL to 21 days, a
Windose user as one might expect.

On Fri, 07 Jul 2006 18:57:54 -0500, Dave Uhring wrote:

> On Fri, 07 Jul 2006 16:30:13 -0700, johndo wrote:
>
>>
>> Dave Uhring wrote:
>
>>> Your ISP's nameserver appears to still have the other party's old DNS
>>> server in its cache. Given enough time and the TTL on that cache will
>>> expire.
>>
>> I thought these things took like 2 or 3 days, at the most......
>
> Depends on how the SOA records were set up on his original DNS server. I
> had an ongoing problem with one ISP who had set his TTL to 21 days, a
> Windose user as one might expect.

BTW, you can confirm whether my hypothesis is correct by using dig.

On Fri, 07 Jul 2006 18:57:54 -0500, Dave Uhring wrote:

> Depends on how the SOA records were set up on his original DNS server. I
> had an ongoing problem with one ISP who had set his TTL to 21 days, a
> Windose user as one might expect.

It is also possible that the ISP in question has the zone designated as
primary in its name servers. It had to do this so as to support the name
when the DNS was hosted there, and it may never have removed it.

The ISP may never have been *told* to remove it, esp. if they were not any
type of contact for the domain.

If the ISP mixes resolvers and public name servers in some way, or if they
store their domains as primaries on their resolvers too, then the
resolvers will still have the zone information from when the ISP was
providing DNS service for that domain. In that case, a simple request to
the ISP for this zone to be removed from their primaries will probably fix
the problem.

Whether this is be the case can be determined with dig. Specify
+norecurse when querying your ISP's DNS resolvers for the domain's SOA.
If there's no ANSWER, or if the answer has no AA flag, then what I've
described is not the problem. If there is an AA flagged ANSWER, then what
I've described is in fact the case.

- Andrew