This is easy to do with the Route solver using the ROUTENAME property. This has been described in the forums many times. Search on the ROUTENAME and you will find previous posts. For example:
There are no limitations on the record numbers. Though loading and working with 2 million may take a while. Have you opened the Stops sub layer's attribute table and verified their are only 71,200 records? The NA Window does not allow you to "expand" the stops there as it will take a long time to refresh that window if their are hundred's of things in it. But will show a accurate number of records that were loaded.
You could also run the GP tool Add Locations to first compute the network location fields on your input data (both sets) and look at the status field to make sure they are getting "located" on the network. Once you have verified that the data is correct then you can load this data into a route layer's Stops feature class using the network fields (not geometry) and the load will go very fast.
Do try by splitting the data. Can you tell me what version of the ArcGIS software you are using and how much RAM is on that machine? It could be running out of memory.
8 GB RAM (HP Z600 WORKSTATION)