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jonnyquest_2564's avatar
jonnyquest_2564
Icon for Nimbostratus rankNimbostratus
Mar 31, 2016

gTLD records from rootDNS process question

Hi Folks,

 

I've two questions which I couldn't find the answers after searching for hours. Hope someone here can help me to figure it out.

 

Q1: When the LDNS trys to resolve a FQDN, e.g. it got four gTLD records from the root server, "DNS-CTC, DNS-CNC, DNS-USA1 and DNS-USA2", which one will LDNS choose to get the next level records?

 

I believe LDNS will always choose DNS-CTC cause it's the first one in the list, or am I wrong?

 

 

Q2: When the LDNS got two records for GTMs, e.g.:

 

lb1.redirect.group.com.212.162.7.99

 

lb2.redirect.group.com.69.74.209.171

 

Which one will LDNS choose to contact first or contact both simultaneously?

 

 

Thanks in advance! Cheers.

 

application delivery
BIG-IP
BIG-IP DNS

1 Reply

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  • IanB's avatar
    IanB
    Icon for Employee rankEmployee
    Apr 01, 2016

    Ultimately it depends on your client, but typical client behaviour is to take them in the order received - that is, try the first one, if that doesn't work, try the second, if that doesn't work, try the third etc.

     

    Some DNS servers will randomise the order that they return records in, in order to more evenly balance traffic. GTM goes a step further than that, and returns the 'best' response (where "best" is determined by the GTM's configuration)

     

    With regard to your second question, where the delegated DNS server returns two NS records pointing your GTMs, it doesn't actually matter which GTM they hit, because all GTMS in the same sync group will return the same answer, given the same question from the same LDNS IP address.