[TriLUG] Slides from last night's DNS Presentation

[Jon Carnes]

> I have a follow up, due to us running out of time.
> 
> It might be worth explaining what lame servers are as those new to DNS
> will most likely see them in their DNS logs and might wonder what they
> are.
> 

I believe a "lame server" is one that does not respond to a dns queury.
All domains have at least two domain name servers so the domain
information my still be available - on one of the other servers - but
the first server you went to for the information did not respond.

Example:

  A person or application using your DNS server tries to contact
www.ftnc.net, to that they need the ip address of the server.

  They send a request for the ip address to your DNS server.

  Your DNS server does a quick check of the .net root domain server
which points it to:
      NS1.TFDA.ORG   216.134.205.133
      NS2.TFDA.ORG   216.134.205.134
as the athoritative servers.

Your DNS server tries to contact NS1.TFDA.ORG for the information on
www.ftnc.net. The server is overloaded or down. The request times out.

NS1.TFDA.ORG is marked as a "lame server" by your DNS server, and it
tries the next server in its list: N2.TFDA.ORG

This server responds in a reasonable amount of time and your user
continues to browse - with just a bit of an annoying wait.

The next time your DNS server needs to find an address for the domain
ftnc.org it will skip the server marked as "lame" - unless you have your
DNS server set otherwise.

Jon