Periodic Busy Signal with UC540 has plagued my phone system!

[williamyeack]

I have had a UC540 with several 7975g phones for several months now and I use Skype Connect as my SIP Trunk service provider.

Throughout the entire time that I have had the system, I have been  plagued by intermittant busy signals.  It seems to happen the most when  nobody has called for awhile (for instance, the first call of the day),  but it sometimes happens more often.

Usually, when a person would call in and get a busy signal, if they  called right back they would get through, but sometimes it would be busy  a few times in a row before getting through.

I have spent many hours on the phone with Skype, Cisco and NETGEAR (my  router is a netgear router) and they all blame eachother and nobody has  been able to help me fix it.

I am not a 'total' tech person but I have set up this system myself and I  know how to get around it 'fairly' well.  The only thing that I am not  great with is CLI.

Here are some of the settings which I believe to be relevant - let me know if you need any more information -

UC540 Settings

Static internet IP address of 192.168.1.3

Default Gateway 192.168.1.1 (which is the IP of the NETGEAR router)

Primary DNS 192.168.1.2

Secondary DNS 4.2.2.2

Network Setup

The UC540 sits behind a NETGEAR FVS336gv2 router with the following relevant settings:

Forwards UDP ports 5060 & 8000-8009 to 192.168.1.3 (IP Address of the UC540)

Static Route 1

Name UC500-Data

Destination 192.168.10.0

Gateway 192.168.1.3

Metric 10

Static Route 2

Name UC500-Voice

Destination 10.1.1.0

Gateway 192.168.1.3

Metric 10

Static Route 3

Name UC500-CUE

Destination 10.1.10.0

Gateway 192.168.1.3

Metric 10

Thanks in advance for all of your help!

[Darren DeCroock · Accepted solution]

Hello William,

I can't really say what the problem is at this point, but there are a few things I would try to see what may be causing the problem.

The first thing I would do, is to run a debug on the UC500 to catch the incoming calls. (Debug voice ccapi inout, Debug ccsip messages.  This can be done in CCA)   If you can do this early in the morning, and call it yourself, to find out if you get a busy signal or not.  If you do, I would check to see if the UC500 is recieving the call.  If it is not, then the problem would appear to be with the Netgear, or Skype.  Another thing you could try, is to just remove the Netgear from the equation, and connect the UC500 directly to the internet connection.  (This could be little work, since I am not exactly of your topology.)

Thank you,

Darren

[williamyeack]

Hi Darren,

I will try that setup tonight after hours - do you know have any idea what could conceivably cause the issue though?

[Steven DiStefano]

William,

Does it ever happen with internal calls calling eachother, or only the incoming SIP trunk call?

If it was what i was thinking, it would happen 50% of the time and that is where you dont have a 1:1 mapping of ephones to ephone-dns.  One of them map have 2 ephone-dns is cases I observered previously.

You have some good advise from Darren I'd say outside of that.

Steve

[williamyeack]

It never happens with internal calls and it never happens with the FXO line (we have 1 FXO line and a SIP Line).  Our incoming phone calls are routed to an Auto Attendant but I was getting the same problem as I am now even without the auto attendant -

Do you think it could be the SIP registration interval?  How do I change it?

[David Trad]

Hi William,

Do you think it could be the SIP registration interval?  How do I change it?

Highly unlikely

I have a sneaky suspicion on what it could be...

So let me get the ingress call topology worked out on this.

• Client calls Sype Number
• Skype talks to the UC
• UC sees that this SIP trunk ingress call has to go to AA
• First time calls comes into AA user busy message?
• Second attempt calls process to AA fine?

I am not sure if you can or not, but can you force your Skype trunk to use G.711uLaw instead of G.729? I am not sure if Skype allow for this as I have never used them, but I am really suspicious of the issue being a Codec Negotiate issue, this is a typical thing I see often with SIP trunks and in particular with the UC's AA

It is a working theory, and would like to eliminate it if we can.

Cheers,

David.

[william.yeack]

Hi David,

Skype told me that I should change the G.711/G.729 on the UC500 and they don't handle it from their end.  Is there a way to make this change from CCA?

Also - I reset the UC500 to factory settings and I put it right up next to the WAN (to remove the router from the equation).  However, I am unable to receive calls at all now - do I need to add entries into the NAT in CCA?

[mcasimirc63]

If you are setting up your UC500 from scratch you might be able to make use of this video I made when I had Skype.  It shows you the setup process

https://supportforums.cisco.com/docs/DOC-16346

[williamyeack]

I solved it!  I reset the UC540 to the factory settings and put it directly in front of the WAN (removing the NETGEAR router from the equation).  After setting everything up again, the problem appears to be fixed.  I have no idea what the router was doing to cause the problem, but I'm grateful to finally have a working phone system!

William

[mcasimirc63]

For future reference, when you have SIP issues just set the SIP provider to none which will erase the entire SIP configuration and then re-create it. 

[paolo bevilacqua]

Thta is the best choice for SIP trunking, but be aware that in doing so you are expose to toll fraud unless you configure security:

http://www.cisco.com/en/US/tech/tk652/tk90/technologies_tech_note09186a0080b3e123.shtml