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DNS BIND

Posted on 2013-01-29
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Last Modified: 2013-02-06
Hello BIND experts,

I'm not a DNS expert. Suppose i have two BIND servers. Both have the entries below:

vpn.pepsi.com.                 in      ns      adns-LA.pepsi.com.
vpn.pepsi.com.                 in      ns      adns-NY.pepsi.com.
adns-LA.pepsi.com.               in      a      1.1.1.1
adns-NY.pepsi.com.               in      a      2.2.2.2


Question#1: Are lookups for vpn.pepsi.com being round-robined or are both A records being returned to the client?

Question #2: If lookups are being round-robined, supposed adns-la.pepsi.com (1.1.1.1) goes down. Wouldn't BIND still try to answer with that record? I assume yes since it doesnt have a way to know that adns-la.pepsi.com is down.
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Question by:trojan81
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Expert Comment

by:Ugo Mena
ID: 38833907
to configure RR on BIND DNS, you would define multiple A records with the same name and different IPs.

adns-LA.pepsi.com.               in      a      1.1.1.1
                                                 in      a      2.2.2.2

adns-NY.pepsi.com.               in      a      3.3.3.3
                                                 in      a      4.4.4.4

or similarly

vpn.pepsi.com                in          a       1.1.1.1
                                         in           a       2.2.2.2
                                         in            a      3.3.3.3
                                         in             a     4.4.4.4

DNS will deliver all the IP addresses defined, the first IP address in the returned list will be in a (default) round robin order (controlled by the rrset-order 'named.conf' statement).
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Author Comment

by:trojan81
ID: 38833920
ultralites, thanks for the explanation. I don't see that in the BIND configs so I assume we are not RR.

So based on my example, when a user does a lookup for vpn.pepsi.com is he querying both ADNS-la.pepsi.com and adns-ny.pepsi.com?
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Accepted Solution

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Ugo Mena earned 500 total points
ID: 38835727
I think it would depend on the routing decisions made based on path, network policies, and/or rule-sets. I would assume the faster/shorter connection would respond first.
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