PMF71, sorry for the late response, just got home from work...nice conference call filled day of convincing change mgmt dept.'s of my custoemrs to allow us to make a change and trying my best to explain the technical areas in english...which I'm not good at I might add
The links at the bottom can answer most of your questions regarding DNS as well....it is a very good resource, with very few mistakes that I spotted (don't ask me to name em off hand, cuz its been about 1.5 yrs since reading it
, mistakes meaning either actual mistakes, or the behavior has been changed in a service pack (wont go into the hotfixes)
I am referring here to your note above:
"ADGod, can you explain why you would need to try and stay away from root hints?
I've been using root hints *only* on my windows server for the past two years, and have had no problems whatsoever. They always work. Never had any DNS problems, except for an odd one within my network."
A: There is no real reason to stay away from root hints...I have actually seen both ways work perfectly fine. Using root hints is a little more resource intensive on the server however, due to having to use more processing power and memory to query the root hints, vs. just passing a request it does not have locally onto specified IP addresses, which of course is quicker and easier. root hints are queried in the order they are listed, from top to bottom if i recall correctly. It is also possible to add more root hints, such as to your ISP, or domain registrar. I believe the caching behavior is the same....I believe all answered queries, whether by recursion using root hints or forwarders, are cached for something like 3600 seconds (yep just double checked thats what it was). I would not expect issues with either configuration (providing it is configured correctly) if you have a smaller sized domain. out of curiosity, whats the odd behavior you were speaking of?
and will go into your original problem statement.....
"I have a new windows 2003 machine that I'm using on my network that serves as (among other things) a DNS server. My initial problem was that DNS lookups were stalling out for about a second before being resolved.
Note: Sounds like misconfiguration of the forwarders, or non recursive DNS servers being the forwarded address (which would log a bunch of events in your DNS log, you will likely see these events occasionally, which is not a worry, its the mass amounts...on another note, I have seen this spike router bandwidth, which could also be a potential culprit...the events (the reason they are being logged rather) could also potentially cause run time errors in DNS service). As a test, try using 4.2.2.2 as a forwarder and see how request times look. After the first query, the result will be cahced for the 3600 second minimum so other requests for the same name will be handled much much faster, since the local DNS server has the information in it's cache.
Forwarders in Win2003 work by specified domain name (conditional forwarding), or a general forwarder address for all other requests that are not cached on the local DNS server. This can be greatly influenced by a few items, including responsiveness of the DNS server being forwarded to, the amount of hops to get to your forwarder, network bandwidth of course, and quite a few quirks that could come in. Let's put it this way, I typically use 4.2.2.2 as a forwarder, since it is public, and it always work extremely well.
My suspicion was that the forwarder wasn't working properly, and Windows was getting hung up looking around to see if it knew were xxx.com was before giving up and forwarding the request on.
Note: what you say here is true...it is lookign around in its local cache for <domain>.com (or <domain>.<domain>.com for that matter), once it finishes that, it will review its conditional forwarders to find out if there is a DNS domain name match, if not, it will move to its general forwarders. If there are no domain names specified in teh forwarders tab as conditional forwarders, it should move directly to the general forwarders. Whereas with root hints, it will review its local cache, then it will check for forwarders, and if none are listed, will move to root hints....if i am recalling correctly...the links below will tell you for sure....all of these processes take time...but it is time in milliseconds...so not necessarily getting hung, but taking longer to get to the forwarder due to hops involved, or something of the sort (typically hops should not be a big issue, but of course, the fewer the hops, teh quicker the request and response)
The reason that I thought this was that if I set a client machine to use the address of the forwarder directly as its primary DNS server (instead of the win2003 server), lookups were very snappy. This ruled out there being a problem with the ISP's server.
Note: This does not necessarily rule out a problem with the ISP DNS servers. The reason for this is that they may be non-recursive, and log so many events from teh DNS server to that effect, that it can cause a run time error in the service, as mentioned above. Again....4.2.2.2 as a test for a forwarder, this will not log any of the problematic errors
I compared and compared settings against another box that had DNS working quite well on, and to the best of my abilities, I could not find anything out of the ordinary.
Note: Assuming a query for an internal resource...you likely would not see anything different, due to internal DNS working perfectly...for query to external resource...if you have one or sporadic machines working good, and the other machines are having the slow queries, there is a potential that it is a client side issue and not server side (would want to look for patterns in os type and sp level, etc.)....for anything like this to be a fair test, you need to run ipconfig /flushdns & ipconfig /registerdns (can reboot instead for good measure)...then try queries and see the behavioral differences
Ok, so now comes the wierd part. I removed the forwarder completely from the Windows DNS, and now DNS lookups are lightning fast.
Note: leads back to issue with forwarder config or forwarder DNS servers themselves
The only address that the server now has is its default gateway, and that (of course) is pointed at my router. All the clients are then pointed at the server for DNS, and it is all working flawlessly."
.....hopefully all this clears it up for you a bit better...questions just ask
dont forget too, you can always make a memebr server a caching only DNS server too to further speed up responses, this can save alot of bandwidth actually in teh long haul
You may find these links helpful:
DNS queries-
DNS-
anything else just ask
-Brandon Wilson
MCSE00/03, MCSA:Messaging, MCSA03, A+
almost got a paragraph there
