The IB tws program needs network access. Although you may well want to have more than one network link to improve system reliability, the configuration and security issues involved with obtaining network connections to the outside world are beyond the scope of this tutorial, and in any case have little impact on shim configuration, since the IB tws serves as an intermediary to the upstream net.
This by no means detracts from the importance of such issues. Although network configuration planning will not be considered furthur herein, it would nevertheless seem prudent to have multiple network connections if you intend to risk real money by making trades with the IB tws. Please also keep in mind that network connections to the IB tws program from the trading-shim require that the tws accept a network socket connection, and that such connections are not themselves secured by password access, so that both your network and your IB tws host must be secure.