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GSLB handing out the same IP every time.


Abhijith KS

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Hi All,

 

Can someone tell me on what basis does Netscaler GSLB hand out the VIP addresses when the client does a DNS lookup. I have a GSLB set up with 4 services configured and I see that most of the DNS responses are with only 1 ip.

 

There is no weight configured nor GSLB persistence, so just want to understand if Netscaler has a control on what IP to hand over at the time of DNS response. 

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"The static proximity method for GSLB uses an IP-address based static proximity database to determine the proximity between the client’s local DNS server and the GSLB sites. The NetScaler appliance responds with the IP address of a site that best matches the proximity criteria."

 

If you test from the same location you might get the same ip.

Also if you use active-passive deployment  you might get the same ip until the site becomes unreachable.

 

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That is right Mihai, I have 2 sites for example :
Site A & Site B

 

Site A subnet - 10.75.x.x

Site B Subnet : 10.200.x.x

Site A has GSLB services of 10.75.1.1 , 10.75.1.100 &  10.200.1.3 , 10.200.1.7

 

Site B also have the same GSLB services.

 

So whenever I or any other user from any region query they get proximity based IP's and we either get 10.75.1.100 or 10.200.1.7 every time. Atleast 90 % of the time.

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to be honest i always used gslb only with 1 services per site for 1 domain name. So 1 domain name and 2 services.

In your case i see you have 2 services/site for 1 domain name. is that true? Why would you need 2 vips for the same content on the same site ?

 

Using static proximity you will get the same ip   bases on proximity.

 

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Yes only 1 domain name and 2 VIP's in each house. So when you configure cross data center we have 4 services i.e. 2 from Site A and 2 from site B configured in both the houses. And this is the standard way becasuse of DNS. When you have a DNS delegation configured on your LDNS the traffic can either hit site A or site B. 
What if DNS query from LDNS hits site A NetScaler and if your site A VIP's are down for some reason. In that case, there will be intermittent failure. In order to avoid this, we configure both the services in both of the houses.
And I believe, this is the standard way to configure GSLB.

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