I am trying to access a web service built by a client that is hosted on their internal servers. They have exposed access to the public internet, but have restricted access to Salesforce's IP range. When I am trying to access their web service, I get an error suggesting the IP restrictions aren't set up right. But I am not sure what is the best way to troubleshoot this. If it was my local machine having problems, I would do simple tests via command line etc., but obviously I don't have those tools available from the Dev Console.
What have other folks used in the past to troubleshoot connectivity issues to a server when it is restricted to SFDC IP ranges?
EDIT: At this point, I get this error in the SFDC Logs:
Access control configuration prevents your request from being allowed at this time. Please contact your service provider if you feel this is incorrect.
I 'think' that is their proxy throwing an error, but I am trying to provide more detail to the client's team to help them fix the issue...