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rugby
I think I know it all.
VIP
join:2000-09-26
Plainfield, IN

1 edit

Comcast SIP connection problems

I'm having some VoIP frustration here. I have Comcast at home in Indianapolis and a hosted PBX in a datacenter there. I use Zoiper to connect to the server just fine from home. I am visiting family in Buffalo Grove, IL and Zoiper will connect to my PBX from here, but I get no audio. No dialtone, no ringing, no voice. I bypassed everything and hooked my macbook pro right up to the modem and I have the same problem. If I establish a PPTP tunnel to the network in the datacenter I can use Zoiper just fine, I just can't use it without the VPN. On a whim I hooked up an ATA in Buffalo Grove and have the same problem. I know the ATA works as it used to be in my office.

So, to recap:

ATA works at my office, not in Buffalo Grove
Zoiper works at my home, but not in Buffalo Grove
If I establish a VPN connection to the datacenter, they both work just fine in Buffalo Grove.

Any ideas?


sragle

join:2005-08-08
San Jose, CA

Sounds like a NAT issue, make sure that if you using more then one SIP device on the same network that both device are using a different local SIP port. If you have 2 SIP device behind the same NAT IP, and using the same local port, the NAT'ing device will get confused where to send the SIP message to.


sragle

join:2005-08-08
San Jose, CA
reply to rugby

have you try using X-Lite? X-Lite seems to be good about dealing with NAT.


rugby
I think I know it all.
VIP
join:2000-09-26
Plainfield, IN
reply to rugby

But I plugged the ATA right into the cable modem and it had a public IP address, along with my laptop running Zoiper, wouldn't that take care of NAT altogether?

My PBX has a public IP address as well.


sragle

join:2005-08-08
San Jose, CA

You using Static IPs with comcast? If you not using Comcast Business account when you plug the ATA right to the cable modem, you need to power cycle the cable modem to pick up the new Mac Address since they only allow one mac address per resident user.

Is there a firewall in front of the PBX and when you VPN in are you connecting behind the firewall? If you are running asterisk you should be able to ssh to the box and run tcpdump and see if the packets are making to the PBX and its the packets that PBX is sending that is not making it to you, that will help let you know at what direction the failing point is happening at.

If you did power cycle the cable modem when you hooked up the ATA to it, then for sure that eliminated a local NAT issue as you stated, and possible a firewall issue local to the PBX box. The PBX box should be allow to receive 2 kind of ports 1st one is SIP port 5060 (SIP Control Port) and the other will be RTSP (Used for Audio) the RTSP is define in the PBX config, in asterisk it is /etc/asterisk/rtp.conf it would be the line "rtpstart" (Starting Port of RTP) and "rtpend" (the ending port of RTP), on the firewall you would need to configure that whole range on the firewall to be allowed to the PBX.



IDunno

@comcast.net
reply to rugby

This is a real long-shot but it seems like the 911 emergency do-gooders got a law passed requiring all new ATAs to be reregistered after relocation.


sragle

join:2005-08-08
San Jose, CA

That law is for VoIP providers not for private box.


rugby
I think I know it all.
VIP
join:2000-09-26
Plainfield, IN
reply to sragle

We don't have static IP's here in Buffalo Grove. I know the ATA works as I've used it in other locations without issue. I can't even get my softphone to work. I've even used it on other Comcast locations (Arizona when I went to visit my parents). It just won't work here for some reason.

I think I've gotten a solution, I"m going to put in a VPN router here as it's a remote extension that's pretty important. I know the VPN works as I've created a PPTP tunnel from here and my softphone works fine.