I've tried with and without ping. Neither really seems to work correctly and I can't really run it any other way but with a windows client. There's no console in the modem interface. Thanks for everyone's help though!

Terminal shell v1.0
Copyright (C) 2013 Motorola Mobility, LLC. All rights reserved.
Motorola Netopia Model NVG589 VDSL/ADSL AnnexA Ethernet
Running Netopia SOC OS version 9.1.0 (build h4d38_1.1)
ADSL/VDSL capable
(admin completed login: Admin account with read/write access.)

NOS/255307918359056> telnetd -l sh -p 9999

Unrecognized command. Try "help".

NOS/255307918359056> telnetd -L sh -p 9999

Unrecognized command. Try "help".

NOS/255307918359056>

I don't think I will be making it to Cambridge although it would be great to meet all you fine people, I just don't travel much and it's really not in the budget.

Stu