Answer Re: A transport-level error has occurred when sending the request to the server Was this post helpful ?

For some reason the connection was made through Named Pipes instead of Shared Memory (the default for local connections), which suggests that SqlClient did not recognize the connection was local, and most likely tunneled Named Pipes over TCP, hence, disconnecting the network has impact.  How do you specify the server name - perhaps by its fully qualified domain name (FQDN), or IP address?  If you specify it by the hostname or "." or "(localhost)" SqlClient should recognize the local connection, and you should not see the error.