[tlug] Re: Absurd DNS failures.

[terranova@example.com]

> When dialled up from Linux, the nslookup command automatically contacts my
> ISP's DNS servers and resolves names like www.yahoo.co.uk, www.yahoo.co.jp,
> and www.att.com.  But it fails with names like www.yahoo.com -- it says that
> it cannot reach any name servers. 
> When dialled up from Windows XP, the nslookup command automatically contacts
> my ISP's DNS servers and resolves all of those names.
> So is there something about the combination of US domain names and Linux and
> my ISP's DNS servers that causes failure?

There could be. First up, there's nothing 'automatic' about it, as I'm sure you realize. Do you know about /etc/resolv.conf? This is where nslookup and other Lx/Ux progs will look for nameserver IP's. Your ISP's nameserver IP's should be in here, but I'm not aware of anything in Lx that does this 'automatically'. 

Let's assume that they are, but that your ISP's DNS setup is faulty, and doesn't have links through to other nameservers. If this is the case, it will succeed with 'local' domain names, but fail with wide area ones.

On the other hand, M$ OS's 'know about' M$'s site, probably including its nameservers, and undoubtedly fall back to them in the event of trouble. This could explain why the M$ dialin succeeds where the Lx one fails.

> Back to Linux, and something that I only reproduced twice in one day because
> this was enough to persuade me that this is unbelievable.
> "nslookup www.asia.microsoft.com" found CNAME records for microsoft.com
> and listed several addresses starting with 207.46.
> But "nslookup microsoft.com" timed out and said it could not reach any name
> servers.

This tends to confirm my doubts about your ISP's DNS setup.

See the references at the bottom of the nslookup man page for more info.

Carl Adams.