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mlamutt_62697
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Aug 19, 2011

Need help moving traffic between data centers

Hi all,

We ran into an issue recently with a site that we are hosting in 2 Data centers. We use dynamic DNS to route traffic between 2 data centers (GTMS and LTMS). Last week we moved a site between 2 of our Data centers to mitigate a potential issue we were seeing. After the 60 sec. TTL, we began to see new traffic route to the new DC as expected. The issue we found was that most of the existing traffic did not migrate over to the new DC after the TTL expired. After an extended amount of time, we were forced to manually reset all the remaining session to forcibly move them to the new DC.

 

 

 

This is an internal site for one of our clients. When we asked them if they were honoring our TTL they replied that this was an issue with active tcp session lifetimes. They said that regardless of TTL, if we still have a device servicing tcp sessions from them that we’re made EARLIER than the “failover”, they will continue to send requests via those active tcp sessions UNTIL they are torn down by RST or timeout.

 

 

 

They went on to say that since our GTM only advertised a new IP, the routed FROM was still “alive”, thus the tcp sessions from the client were still “valid”. If the our device was told to “reset” the connections, they would have initiated NEW connections to the NEW data center.

 

What is the best way to move traffic between our DCs without having to forcibly kill the connections?

 

Thanks for any advice,

 

Mike

 

 

 

 

 

 

1 Reply

  • Hi Mike,

     

     

    If their client(s) don't do a DNS lookup while using an active TCP connection, I think you'd need to reset their connections to force a lookup and move to the other datacenter. I guess you could proxy traffic to the new datacenter with an iSession tunnel, but I think that defeats your point of moving traffic to the second datacenter.

     

     

    What protocol(s) are you servicing? Is there a concept of redirecting the client to a new FQDN which is specific to the other datacenter? Or a way to force the client to do a new DNS resolution which doesn't involve resetting the connection?

     

     

    Aaron