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ADC GSLB DNS reply Question

Chris Craddock

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Dear Community,


I have GSLB set up for a multitude of services. One Netscaler lives at our Main Data Center while the NS that makes up the other side of the GSLB lives at our DR DC. Both DC's are directly connected via DCI cross connect so they have direct communication between eachother. My question is this. If a client does a DNS lookup for one of the GSLB services that the NS is authoritative for, how does GSLB decide which Netscaler responds to the DNS query? How do I know if its the NS at my primary DC or my DR DC that responded to the query? 


Thank you.

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And to add to Carl's statement, so either gslb-participant responding is a good thing, the point is that during normal operations if your GSLB is configured for Active/Passive, then both will return the primary IP for the dns resolution and only if it is down does the backup ip get resolved instead. 


Having both participate in the DNS response is essential that if the entire primary site is down, the backup DNS (adc) will be queried to hand out its own IP to the dns response.


So you have redundancy for both the DNS resolution and the resource delivery (vip) itself.

See https://support.citrix.com/article/CTX123976 (PDF has more info than in just the article body)

and https://support.citrix.com/article/CTX122619


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