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Old 11-17-2009, 07:54 AM   #1
Registered: Sep 2005
Posts: 861

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Strange VOIP Problem

Hi guys,

I am encountering a strange problem on my VOIP setup. Basically, I have a asterisk appliance IP04. I have setup all the extensions and everything. I use a Linksys PAP2T as an ATA remotely. Now, my problem is the ATA sometimes is okay can call SIP and PSTN but sometimes I just can't hear anything. I thought it was my ISP blocking the VOIP packets but I have tried both the SIP softphone and IAX2 softphone on my PC. For IAX2, it works perfectly however in the SIP, I can hear the other end but they cannot hear me.

These are the ports I have opened on my router

1.) UDP 5060 - SIP Port
2.) UDP 10000 - 20000 - RTP Port
3.) UDP 4569 - IAX2

Do I need to open both TCP/UDP for these ports or UDP should be enough?

These are the test cases:

1.) Using my Wifi Connection and a analog phone connected to ATA --> Sometimes working sometimes not and sometimes you can call SIP but the other end cannot hear you
2.) Using IAX2 in wifi connection --> This one works perfectly
3.) Using a mobile phone connected to Wifi Network --> The same...but you can call and go out on PSTN but the other end cannot hear you
4.) Using a mobile phone connected via 3G --> Works perfectly but as expected it is quite slow and voice quality is awful

Can you suggest what is wrong? I am really lost here. I want to use SIP rather than IAX2 because it is widely used and since my ATA doesn't support IAX2.

Are there other ports I need to open or configure?

Thanks in advance.
Old 11-17-2009, 10:08 AM   #2
LQ Newbie
Registered: Jul 2009
Posts: 28

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I have had similar problems in the past, with great audio one day and nothing the next, and the best I can figure is that the service provider was doing something bizarre with those ports. For me, the solution has been to change the ports SIP and RTP are using away from the defaults of UDP/5060 and UDP/10-20k. SIP, RTP, and RTCP all operate over UDP exclusively.

Failing that, taking packet captures at each hop in the network would help narrow where things are breaking down.

Edit: This is also the poster child problem for firewall or NAT issues. On both ends, your firewalls are set to accept both incoming and outgoing traffic on those ports?

Last edited by gratuitous_arp; 11-17-2009 at 10:11 AM.
Old 11-17-2009, 10:30 AM   #3
Registered: Sep 2005
Posts: 861

Original Poster
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Hi gratuitous_arp,

I have only firewall opened on my base station where my asterisk is located. I did not open anything on client side. Though, I have tried to put it on DMZ but still no luck.

By the way, what ports have you tried that worked?



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