"Underline connection was closed" "Unable to connect to the remote server"

A customer was getting following error which is very generic error and come in many scenarios.

“They are running some code which returns "Underline connection was closed" or "Unable to connect to the remote server" with Cisco Load Balancer and 2 servers.


Networking team found that some time in the code the server A makes a request for nslookup on the VIP and then reaches the server B. And since the server ”A” and server B are on the same subnet the server b replies directly to the server a. So the server “A” sees that this reply is coming from a different IP (IP of server B) and ignores it.



Work Around: putting up an entry in the host file on both the servers for itself on the http request.