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Shweta GargShweta Garg 

System.CalloutException: Unable to tunnel through proxy. Proxy returns "HTTP/1.0

Hello Developers,

While calling webservice from Salesforce Org,I am getting an Exception "System.CalloutException: Unable to tunnel through proxy. Proxy returns "HTTP/1.0 ".I have made a lot of search and found that This is a Firewall issue.
I have added these IP ranges in my Salesforce Org.

204.14.232.0/23 East Coast Data Center (set one)
204.14.237.0/24 East Coast Data Center (set two)
96.43.144.0/22  MidWest Data Centers
96.43.148.0/22  MidWest Data Centers
204.14.234.0/23 West Coast Data Center (set one)
204.14.238.0/23 West Coast Data Center (set two)
182.50.76.0/22  Japan Data Center

here 204.14.232.0/23 .->  204.14.232.0 - 204.14.233.255
I have added the IP address Like this. But Still I am getting the same issue. I suspect  these ip address should be added at the server side(where web service resides)?Am I right. Or i am doing mistake while adding IP address.
Please suggest me with your ideas.