RE: Windows 2008 DNS? Very slow internet

Often in the process of deploying a new server and DNS in an existing
environment, a bad DNS FORWARDER record gets left behind in your new DNS
server. The problem doesn't present itself until you decomission the old DNS
server. Your new DNS server is very slow with external DNS lookups because
it forwards requests to a DNS server that no longer exists. This process
eventually falls and finds and alternate DNS path for resolution.

To correct this problem look for and remove the "dead DNS forwarder" records
from your new DNS server.

Open the DNS manager,
right click on the DNS server and choose properties,
select the FORWARDERS tab,
remove and invalid DNS server forwarder records.

Resolution should be imediate without restart.

"dor" wrote:

> PLEASE HELP!!!
> We just installed a completely new Windows 2008 domain with 2 servers,
> one running DNS. Everything is working great except the internet.
> The pages come up but its soooo slow to load the pages. We checked
> with ISP and all speeds are above normal.
> What could be causing this…internal DNS problem?
> We have DHCP enabled for all clients with the servers IP address being
> handed out for DNS. The server is using itself for DNS and has all
> static IP info in.
> Any help would really be appreciated!!
> Thanks
> Dor
>
>

"David Smucker" <> wrote in message
news:E2588DAB-AC27-47CD-909B-...
>
> "dor" wrote:
>> PLEASE HELP!!!
>> We just installed a completely new Windows 2008 domain with 2 servers,
>> one running DNS. Everything is working great except the internet.
>> The pages come up but its soooo slow to load the pages. We checked
>> with ISP and all speeds are above normal.
>> What could be causing this…internal DNS problem?
>> We have DHCP enabled for all clients with the servers IP address being
>> handed out for DNS. The server is using itself for DNS and has all
>> static IP info in.
>> Any help would really be appreciated!!
>> Thanks
>> Dor
>>
>>
>
> Often in the process of deploying a new server and DNS in an existing
> environment, a bad DNS FORWARDER record gets left behind in your new DNS
> server. The problem doesn't present itself until you decomission the old
> DNS
> server. Your new DNS server is very slow with external DNS lookups
> because
> it forwards requests to a DNS server that no longer exists. This process
> eventually falls and finds and alternate DNS path for resolution.
>
> To correct this problem look for and remove the "dead DNS forwarder"
> records
> from your new DNS server.
>
> Open the DNS manager,
> right click on the DNS server and choose properties,
> select the FORWARDERS tab,
> remove and invalid DNS server forwarder records.
>
> Resolution should be imediate without restart.
>
>

I wouldn't exactly put it that way. And I wouldn't call it a 'dead'
forwarder. It may not necessarily manifest itself when decommissioning a
server, rather it can manifest itself at any time.

If a DNS server that is set as a Forwarder is no longer functioning, or if
whomever owns the server decides to disable Recursion, which will make it
not respond to queries to zones it does not host (effectively making it a
content only server), or is controlling it by "views" ( a BIND feature to
control what subnets it responds to for queries), then the DNS service will
follow a time-out (TTL or Time to Live) algorithm when it sends the query to
the first Forwarder in the list. If there is no response (NULL response)
after the TTL, then it eliminate that Forwarder for this query only, and it
will then send the query to the next Forwarder in the list. If none of the
Forwarders respond, the DNS service will then send the query to the Root
Hints to devolve the query.

Now - and this is an important "now," if there are many DNS servers listed
in the Forwarders list, such as 3 or 4, the time out value for the number of
Forwarders listed may exceed the timeout (TTL) the client side resolver
service is set to by default (on the client machine making the request),
therefore receiving that familiar 'HTTP 404 not found' in the browser.

For practical purposes understanding the TTLs, I would suggest to never set
more than two Forwarders.

To find out if a DNS server will respond to queries and be eligible to be
used as a Forwarder, you can test it by using the nslookup utility (use
set -d2 option and look for 'recursion available' or 'recursion not
available'


--
Ace

This posting is provided "AS-IS" with no warranties or guarantees and
confers no rights.

Please reply back to the newsgroup or forum for collaboration benefit among
responding engineers, and to help others benefit from your resolution.

Ace Fekay, MCT, MCITP EA, MCTS Windows 2008 & Exchange 2007, MCSE & MCSA
2003/2000, MCSA Messaging 2003
Microsoft Certified Trainer

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