Comcast ISP - modem with VOIP passthrough

[mchriss]

I have Comcast ISP. Five years ago I bought a Motorolla SB6121 modem, worked well. I have a Cisco IP phone provied by my employer, connected to my router, worked great. Two years ago Comcast informed me if I were to get a new modem I could get much faster speeds. I bought a Motorolla MG7550, it did improve my speed but VoIP phone no longer works. Motorolla tellls me none of their modems support VoIP. I had Comcast activate my old modem and the IP phone works.

My question is what cable modem will allow VoIP pass through and provide high speed. The Netgear CM1000 is is comcast approved for the speed I want, will it allow VoIP pass through? I do not want to use comcast's phone service. A modem with an analog phone port is not what I need. I am amazed how hard it is to find info for this.

[FURRYe38]

I would check the data spec sheet for the CM1000 to see if it has any of this information.

Might contact one of the forum moderators as well.

@vkdelta 

[vkdelta]

How did you connect your cisco phone behind SB6121? (I know SB6121 has just 1 ethernet port and you will need some kind of switch or a router to connect your router or a PC along with your cisco VoIP phone).

I am not aware of any "voip passthrough" service which comcast sells

.

What may be happening is that you might have had Multiple Public IP service which enables your Cisco IP Phone to get Publicly routable IP and makes it work flawlessly. While this could be accomplished with a router but I have seen some router firewalls playing