the phone number in address book has to be configured to some IP Address.
Desktop MFC scan centers dont dial out.
If 9100C has some kinda setting where after you scan / print - it pops-up at the workstation >> then it's definitely by IP Address.
i'd start by looking at the numbers / properties.
Going to the workstation and checking if there is any "desktop software" configured to receive from 9100C
Also try to setup a workstation with the 9100C installer software and see if it can auto-detect 9100C
Disable firewall and try that.
Let me know how this goes.