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How Does DNS query ns servers.
Okay, this is going to tax some of your brains, but here we go.
Lets say I have 4 ns records for a said subdomain(s). When a dns server queries to get these record(s) it is sent a list of ns records from my upper level ns server, cloudflare. It then queries said ns record(s) and gets an answer for A or AAAA.
My question is do modern dns servers query NS via a round robin, or do they query all to decrease look up times / test to see which is the best / closest host?
I.e. the dns server already has the ns records, and it now needs to look up the exact subdomain A or AAAA record. How does it make its choice on what to query for said subdomain record.
Comments
It seems that (from my googleing) that each time a DNS query is sent to the host the IP in the response is rotated, giving a diffrent record to each question given to the dns server. IDK how true this is, but here you go:
http://en.wikipedia.org/wiki/Round-robin_DNS
From my knowledge authoritative DNS are queried in random. If one fails, recursive DNS would query another authoritative DNS server.
source
It has to be round robin. If it does what you've described then it's Anycast.
wouldn't there be an advantage of query all, and then which one ever has the fastest response use?
Anycast is a concept at the IP level afaik, not at the application level (DNS). If so, then doing anycast DNS would be absolutely pointless...
Is a waste of traffic.
A waste of traffic? How much traffic do you get on your DNS servers? I mean like ~12 gigs a month is how many queries?
Also Which NS records take priority? the 4 you set at your registrar or the 5 you set in NS records?
Dunno, then ask to the creators of the protocol why works like this.
you're doing it wrong if your DNS is using ~12gb of bandwidth.
it isn't, I was trying to point out the fact that it doesn't even use that much bandwidth.
Try: dig +trace yourdomain AAAA (or whatever record type) to see it walk the path. Use dig +trace @ns to start directly with ns in the chain to see what happens.
thanks unused, seems that it is round robin. Sorta what I thought.
I thought it was a more-or-less random selection. Though with 3 nameservers I see a consistent pattern:
ns1 handles the most queries
ns2 handles fewer
ns3 handles the least
The 4 you set at the registrar are the only ones used. AFAIK
@sleddog interesting so registrar takes priority over dig NS?
@bdtech - maybe start with reading RFCs etc to understand whole process ...
or watch this http://www.youtube.com/watch?feature=player_embedded&v=vZ007Vi5HIM
Thanks. I was waiting for your answer in this thread
@gbshouse, I understand that. Just wasn't sure what the current thinking process of how to find said address was in modern servers. I looked at a ton of google searches, and because it is such on odd request very few informative answers came up.