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Optimize Bind DNS Faster Resolve for use with  Exchange 2003

Posted on 2011-03-23
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Last Modified: 2012-05-11
Hello:
I have an Bind DNS with linux for resolve external DNS, works fine but now we are having problems with our Exchange 2003 for faster resolve DNS, I would like know if exist an tune up config of the DNS zone that would help to the Exchange 2003 resolve faster the external DNS. Here is the actual zone file:

$ORIGIN legalpublishing.cl.
$ttl 3600
legalpublishing.cl.      IN      SOA      eros.legalpublishing.cl. postmaster.legalpublishing.cl. (
                  2011031403
                  3600
                  900
                  1209600
                  43200 )
legalpublishing.cl.      IN      NS      eros.legalpublishing.cl.
                        NS      secundario.nic.cl.
                  A      200.111.176.219
                  MX      10 mail.legalpublishing.cl.
curso.legalpublishing.cl.      IN      A      200.111.176.214
elearning            A      200.111.176.214
eros                  A      200.111.176.219
estadisticas            A      190.151.57.18
marketing            A      190.151.57.19
intranetrrhh.legalpublishing.cl.      IN      A      200.111.176.218
lexnxt4                  A      192.168.5.69
lngscldvl01.legalpublishing.cl.      IN      A      200.111.176.212
lngsclweb01            A      190.151.57.18
lngsclweb02.legalpublishing.cl.      IN      A      200.111.176.211
mail.legalpublishing.cl.      IN      A       200.27.203.28      
                  MX      10 mail
ns                  A      200.111.176.219
productos            A      190.151.57.18
productos2            A      200.111.176.211
saad.legalpublishing.cl.      IN      A      200.111.176.217
seminario            A      200.111.176.214
servicios             A      190.151.57.18
streaming            A      200.111.176.214
training.legalpublishing.cl.      IN      A      200.111.176.213
ts.legalpublishing.cl.      IN      A      200.111.176.215
video                  A      200.111.176.214
www.legalpublishing.cl.      IN      A      190.151.57.18
bo                      A       190.151.57.18
bo2                     A       200.111.176.211
www2                    A       200.111.176.211
servicios2              A       200.111.176.211
dj2010                  A       190.151.57.18
dj2011                  A       190.151.57.18
bo99                    A       200.111.176.212
www99                   A       200.111.176.212
productos99             A       200.111.176.212
servicios99             A       200.111.176.212
www1                    A       200.111.176.210
www3                    A       190.151.57.19
productos1              A       200.111.176.210
servicios3              A       190.151.57.19
bo3                     A       190.151.57.19
productos3              A       190.151.57.19
servicios1              A       200.111.176.210
bo1                     A       200.111.176.210
sip                     A       200.73.52.12
conference              A       200.111.176.220

200.27.203.28.legalpublishing.cl.      IN      PTR      mail.legalpublishing.cl

Thank you so much for your help.
Regards

Jose Luis Palacios
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Question by:josepalacios
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by:m_walker
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Why do you think exchange is slow with the DNS?

If exchange is accessing your local DNS server for local records as per your zone file, it should be more then fast enough for exchange.

If exchange is slow in trying to get an external IP address, the there could be an issue in your named.conf file.

One common slow dns lookup is the reverse (ptr) record for an internal IP (eg: 10.1.2.3)  If you dont have this zone setup, and exchange asks for it then it will try to send that to up-stream dns server and search for it and never find it, thus slow.  If you setup the zone (in-addr.arpa for your inside range) even if it has no ptr records, your dns server will get a fast response (even if not known).

So to help out I think we need to understand what is slow.
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by:josepalacios
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I have the the ptr and reverse DNS working fine, well that was a suggestion from an "expert exchange guru", I was checking everything it's fine or at least agree with th most common DNS parameters, only said that but not exactly what would be change for get better performance.

JL
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m_walker earned 500 total points
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I have never tuned dns as such as I have always found bind to be very fast.  Speed and performance issues tend to be around how things work.  I am more then happy to be corrected here.

The way I see it is a stock setup where you have a flat zone file (no updates allowed) and every host has an A record.  I cant see anyway to tune that to get faster.  If you DNS server is under heavy load (lots of lookups) then adding more DNS slaves will help spread the load.

As in you zone file you dont have any trick redirects or the like that could create more lookups or bigger data packets to get the IP requested. eg: CNAME, so its looks about a sinple as it gets.  BIND loads the zone file into memory at startup, so little to no hdd access to do lookups.

If your IP Addresses are static (ie: not changing) you could increase the TTL from 3600.
What this 3600 ttl does is tell other dns servers/caches (windows has a simple dns cache it uses on each computer) is that it can keep using the IP Address for that host for 3600 seconds without asking the dns server again.  So you exchange server will only ask the dns server for that record once per hour.  You can increase that so it will ask less often.  But lets face it, 1 ms every hour is not a bottle neck.

If your DNS server is a caching name server (for internet lookups) then you can look at a few differnt things.
1. No Forwarders.  In this mode, if you dns server does not know the address it will work it our from the root name servers.  
Pro: You should always get the right answer (or at least as correct as any other name server)
Con: May not be as fast as using a forwarder.

2. User forwardes.
Pro: Your ISP DNS servers may be faster then yours, bigger boxs faster data links, aready have the value in cache.
Con: There DNS Server could have bad data that you will get.

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by:Glen Knight
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This question has been classified as abandoned and is closed as part of the Cleanup Program. See the recommendation for more details.
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