When I dial out or receive a call on my Cisco VOIP 7960 I cannot hear the caller on the other end. Help!?!?

Question

OKay here's the situation. I have a Cisco VOIP 7960 series phone. I have an RCA DCM425 Cable modem with service through Time Warner Cable. I also have a Belkin FSD5231-4 Router. The VOIP service is through Pingtone. The phone was programed by my boss (computer science degree). When I dial someone from the phone, As soon as I connect to the person on the other end, I cannot hear anything. But they can hear me when I speak through the mouth piece. When they call me, the phone will ring. But again, the same thing happens. The can hear me but I cannot hear them. Too make sure the phone was not defective, I sent this phone back to my boss and they ordered a new phone direct from the seller. So, this is the second phone and the same thing happened. I disconnected the phone from my router and plugged it directly into my modem. The phone could not Configure to Pingtone. I plugged it into my Belkin Router and it connects to Pingtone in 5 minutes. Please help me resolve this situation.

Answer 1

Did you try calling the phone company?? There are issues in the switchboard that would cause this.

Just a suggestion.

Answer 2

This is a complex topic... but, I'll give it a shot...

The problems you are experiencing are typically caused by your NAT Router/Firewall blocking essential PORTs required for proper function of VoIP comms.

1.

Connecting directly to the Modem will not work - as you saw from your test.  This is because IP-Phones/ATA adapters "typically" will not work directly connected to the Internet.  The IP address ranges are not compatible.  This is why the IP-Phone connected to PingTone behind your router and not in front of the NAT-Router.  Your NAT-Router is designed to connect direct to the Internet, whereas IP-Phones/ATAs are not (different IP range compatibility).

2.

What you need to do is connect IP-Phone behind NAT-Router again.

A.

If you know how, give the IP-Phone a "fixed" IP address in the DHCP range of the Belkin router (e.g.: 192.168.2.5 ), as long as it is address not in conflict with your PC or other device behind router.

B.

Configure the Router to open DMZ for IP address 192.168.2.5 , or whatever IP address the Cisco 7960 is being assigned by the DHCP server, or is preset to use as fixed address.

Any device placed in DMZ has ALL PORTS OPENed to it.

Now, see if it works making VoIP calls.

C.

If it works in DMZ, then you know problem is a port forwarding/blocking issue.  

You can either leave it in DMZ (not recommended for security reasons), or turn off DMZ and enable Belkin router Port Forwarding for specific ports required by the IP-Phone.

3.

To know which ports need opening (incoming ports), you need to know which VoIP protocol the Cisco 7960 is set to use with PingTone i.e. SIP vs. H.323?

SIP Ports

AT a mimimum, to use SIP you need UDP ports 5060 (or 5060-5065) for call setup, and an RTP range (possilby 16384-20000 UDP) for voice real-time data.

H.323 Ports (not positive on this?)

Ports 1717-1720 UDP ,1731 TCP for call setup, gatekeeper and audio.

Whatever NAT/Router port forwarding configuration your boss is using at work is what you need to try and duplicate at home.

Good Luck.