Marketo Support should be able to answer your IP address questions in a jiffy. You can submit a Support Case ticket via your Support Portal. Navigate there by clicking on "How Can We Help" then "My Cases" and selecting "New Case." If you get a message saying that you do not have access, then you should talk with your admin or Customer Success Manager to have your credentials added as an Authorized Support Contact. Keep in mind that the default level of support only allows for a max of 4 Authorized Support Contacts.
I hope that helps!