Unable to IP dial to an internal Polycom video conferencing system

My apologies for the dual posting (Cable/Modem).

We are new to Comcast Business and have a question about configuration. We have a Polycom video conferencing system. It is connected directly to the Comcast modem. An IP address 10.x.x.x was assigned to it automatically from the modem.  We are able to IP dial out to other sites. But other sites are able to IP dial into the Polycom. I read some of the articles in the knowledge based and some suggest the following. 

Enable Bridge Mode – Do we need to assign one of the five usable static IP address to the Polycom?

Router – Connect the Polycom to a router and then the router is connected to the modem.

Any help would be appreciated.

Thank you.