DNS server fail error or dns fail to resolve hostname at virtual machine

I have a virtual machine at portal.azure.com and I configure active directory and I also installed and configured salesforce identity coect to syn my active directory users in salesforce successfully and also configured my salesforce for single sign on. Its working fine at same virtual machine but when I try to login in to my salesforce using single sign on button from other networks its giving me an error msg that dns server not found.

Please suggest step to resolve this problem or where I'm missing configuration at virtual machine for dns server.