you can create a custom property on that interface and add any name on that like wan, mpls, int etc. After that you can create a traffic report through web console or by report writer and filter the nodes by its interface (name you added on that interface). By this you can fetch the data of any particular node or interface.
There are a few different ways to accomplish this but lets start with the Web Based reports.
A good resource for learning how to build these is here http://www.solarwinds.com/documentation/Orion/docs/WebConsoleReportingGuide.pdf
Try the following:
From the Orion web console Navigate to Settings -> Manage Reports. Click Create New Report
1. Add a Custom Chart Resource
2. Select Objects using your preferred options and give your Selection a name, i.e All Interfaces Named Dialer2 You could choose Static Object, Dynamic Selection based on certain criteria as anil.singh mentioned using a custom property on the interface would be a really nice way of going this per customer. See here for details on how to create custom properties
3. When you click the "Add to Layout Button" you will brought to the Layout Option. Click the "Add Data Series" button for the Left Y-Axis
4. When adding the Data Series, Choose the required metric eg Total Average bps (Transmitted + Received)
5. Finally Choose the Sample Interval
6. Review the resource to check it is what you expected.
Sales Engineer - Solarwinds