IP connectivity with Xfinity

[SW7259]

I have a Cisco SPA508G IP phone. How do I hook that up to my Xfinity router/modem?   Comcast says just hook it into the Tel. 1 jack, but the phone doesn't have a telephone jack on it, only Ethernet ports.

[CCAndrew]

If you have Xfinity phone service, it’s not going to work at all

[SW7259]

Thanks for your reply.  Can you help me unerstand why Comcast advertises Xfinity Voice as "an IP, Internet Protocol communication services that are enabled to offer voice functionality which are multy-directional and efficient", when they don't work with an IP phone (Cisco)?