I have an IP phone that has been working, the customer just changed out the modem, I am connecting to the SL1100, but no audio, display reads can not sent RTP packets. What could be the cause? Thanks

UDP is not being passed.

Thanks,I'll check to make sure the ports are forwarded.

UDP forwarding is correct. Now the voip phone can transmit, but not receive. I called my cell, from the voip phone, voip phone transmits but doesn't receive my audio from my cell, place the call on hold, at the voip phone, and I get the MOH. I am getting intercom dt.

Well the problem is you modem (obviously). Better question is what end is having the issue? Where was that modem switched out? Do you have any other phones out in the field with this issue?

I am assuming the cable modem switched? Put the modems WAN Ip address in the SL.

Modem changed at the SL100 side. Everything on the Ip phone is working, DSS,CLID,display,ICM DT, can answer an inbound call. I can access a line on the IP phone, I don't get DT, but can dial my cell phone, answer the call on my cell phone, talk from the IP phone to my cell phone that answered the call , but when I talk from my cell phone to the IP phone, I don't here the audio from my cell phone on the IP phone. Time for a reset?

Might want to try that. But, if I were a betting person that modem doesn't sound like it's in a gateway configuration. Like you have a router behind a router which won;t work without serious tweaking if at all.

I should have bet you. The reset cleared the problem. Thanks Coral Tech.