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Simple DNS Authority Question

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Jay Bollyn
Honored Contributor

Simple DNS Authority Question

Here is a simple DNS situation. I have a hunch about it, but I would appreciate if someone could confirm my hunch, and perhaps elaborate.

Our main University IP address is 66.99.13.58. When I enter this IP addr in nslookup at work (using our DNS server 66.99.13.51) I get www.neiu.edu, as expected.

When I enter 66.99.13.58 in nslookup at home, using one of the DNS servers for attbi.com (63.240.76.4), I get:

*** ns6.attbi.com can't find 66.99.13.58: Server failed

Yet when I enter 66.99.13.58 in the IE address bar at home, it displays our NEIU home page.

I THINK IE is able to display the NEIU home page, because it does not rely strictly on my local DNS server for a non-authoritative answer. It subsequently queries the Authority for this IP addr range (sun1.neiu.edu.) and displays the home page.

Thanks for any info / detail / direction.

(I already have 'DNS and Bind, 4th Ed.' I am trying to build a basic understanding of DNS / bind.)

:-) Jay
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Willem Grooters
Honored Contributor
Solution

Re: Simple DNS Authority Question

Jay,

What happens if you enter "www.neiu.edu" as URL-address instead of the address at home?
If that fails, the _name_ is unknown outside the university domain. Probably there is no DNS server in your campus that exports these (internal) addresses, is authoritive for external resolutions, or DNS communication (port 53) is locked by a firewall. I think this is the point since using the IP address succeeds - no translation will be done (authoriative or not).
You _could_ try to set your server to the internal DNS server at your university (that is: 66.99.13.51) but that may fail - because of above restriction.
Another possibility is that DNS in that machine is limited to certain networks or mecahines - where external have no access.

Willem
Willem Grooters
OpenVMS Developer & System Manager
Jay Bollyn
Honored Contributor

Re: Simple DNS Authority Question

Thanks Willem,

I am able to display the NEIU home page in a browser using either the IP addr or the URL. I posted this question to get a better understanding of DNS.

We are having a problem with a remote database vendor, who authenticates our requests by IP addr range. For some reason, recently we are getting blocked instead of passed through, and no one seems to know why.

:-) Jay
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Edwin Gersbach_2
Valued Contributor

Re: Simple DNS Authority Question

I first thought was that backtranslation fails somehow, but when I did nslookup on my workstation, it corectly returned 'www.neiu.edu'. The problem may be with the DNS server of your provider.
Edwin
Robert Atkinson
Respected Contributor

Re: Simple DNS Authority Question

Jay,
you don't say where you're doing the NSLOOKUP from, so I'm assuming it's an Alpha box running UCX or TCP/IP Services.

Check your DNS setup to start off with. Are you using local DNS or are you forwarding to a Windows DNS server?

If you're forwarding, then your setup should look something like this :-

ALPHA_ROB$$ tcpip show name

BIND Resolver Parameters

Local domain: tbs-ltd.co.uk

System

State: Started, Enabled

Transport: UDP
Domain: TBS-LTD.CO.UK
Retry: 4
Timeout: 4
Servers: codc-1, codc-2, codc-3
Path: UK.RANDOMHOUSE.COM, uk.randomhouse.com

Process

State: Enabled

Transport:
Domain:
Retry:
Timeout:
Servers:
Path:
ALPHA_ROB$$

You also need to make sure that the Windows DNS server is configured to allow you to lookup DNS entries.

Robert.
Jay Bollyn
Honored Contributor

Re: Simple DNS Authority Question

Thanks to everyone for the input. I will continue to read up on DNS and bind.

:-) Jay
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