On 4/5/2011 8:23 AM, iharrathi....@orange-ftgroup.com wrote:
Hi,
can i make priority on a A or NS record? Since with round robin if i
put the same record record 2 or 3 time, Bind ignore the duplicates
Records, means
this:
wikipediaNSns2.wikimedia.org.
wikipediaNSns0.wikimedia.org.
is the same like this:
wikipediaNSns2.wikimedia.org.
wikipediaNSns0.wikimedia.org.
wikipediaNSns0.wikimedia.org.
In this 2 case it will send 50% of traffic to ns2 and 50% to ns0;
Is there anyway to enable priority on A or NS record?
Thanks.
For NS records, there is no way to do this in BIND, and it's completely
unnecessary anyway, since every major DNS full-resolver implementation
will keep track of how fast nameservers respond -- based on round-trip
times, known as "RTT"s -- and prefer faster-responding nameservers over
slower-responding ones. So the load spreads itself automatically, and
failures -- which are assessed as really "bad" performance -- are routed
around.
For A/AAAA records, there are mechanisms to control the order in which
the records are presented. See "sortlist" and "rrset-order" (not sure
that "rrset-order" even exists in later versions of BIND, since I've
never used it in production). However, these are only practical on
tightly-controlled intranets, where all of the BIND-instance
configurations can be kept in sync with each other, otherwise one BIND
instance may undo the careful address-record ordering that another
performs. rrset-order and sortlist are pretty much useless for Internet
names, since the vast majority Internet users get their DNS through
intermediate resolvers, which will usually randomize or round-robin the
responses whenever they are answering from their caches.
As another poster pointed out, SRV records provide the capability for
the domain owner to implement per-name failover and "weighting" of
targets, in the DNS data itself. But, thusfar the DNS community hasn't
had much success getting client-software developers (e.g. browser
developers) to adopt SRV record support. Meanwhile, certain
network-hardware companies (including among others a certain huge router
vendor) rake in big money with their sledgehammer "load-balancer device"
approach to the problem. There are software approaches to network
load-balancing as well, but I have no direct experience with those.
- Kevin
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