Nicely done!
At 09:15 PM 09/24/2001 -0400, you wrote:
>>Ok.. once and a while when researching mail problems I see a message
>>about invalid glue at root from DNSREPORT.COM .. Can anyone enlighten
>>me as to what glue at root is...
>
>"glue" usually refers to A records in NS lookups, that weren't
>specifically requested, but are needed. For example, if I want to find
>the A record for www.declude.com, I first need to check with the root
>servers to find the NS record for declude.com (the nameservers responsible
>for handling DNS requests for the declude.com domain). The root servers
>say they are udns1.ultradns.net and
>udns2.ultradns.net.
>
>So the question is, how do I figure out what IP address udns1.ultradns.net
>and udns2.ultradns.net are? The answer is that the root server has to
>tell me; that's the "glue". If they didn't tell me, I would have to look
>up the A record for those two domains, but would have to look up the NS
>records first. And what if their DNS server was at declude.com? Then I
>would have to go to the nameserver for declude.com to get the IP address
>of udns1.ultradns.net, but in order to find the nameserver for
>declude.com, I would need to find the IP address of udns1.ultradns.net,
>causing an infinite loop.
>
>I believe the RFCs require the glue to be there for root servers, and
>other DNS servers that are the start of a new zone. Every so often, a
>root server won't give out the glue -- I have no idea why it would not,
>though. I only recall seeing this happen with some of the country TLDs
>(such as .uk). And, when it happens, it seems that some of the root
>servers will have the glue and others will not.
>
>>... what a customer would need to do to fix it ...
>
>That I have no idea of. I guess the first step would be to ask the people
>who are in charge of the root servers for the TLD (.uk, .com, whatever)
>why the glue isn't being sent, to see if there is a valid reason. If not,
>yell at 'em.
>
>>and how it might impact mail delivery?
>
>At the very least, it will slow down mail delivery. That's because
>unnecessary DNS lookups need to be done. Instead of 2 packets being sent
>(1 to root asking for the NS for the domain, and 1 to the NS asking for
>the MX record), 4 or more packets may need to be sent (you also need to
>send an NS for the NS you had requested, and an A for that NS).
>
>---
>
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