Tollfree Call Routing on CUCM over SIP trunk

[Mohammad Azzeh]

malbaqari  bro can you help me with this one?

[Vivek Batra]

Do you have SIP on both call legs viz between CUCM/gateway and gateway/provider?

Please also share the output of debug ccsip messages and show run.

- Vivek

[Mohammad Azzeh]

here is the sh run and the debug

calling number 4456, out mask 3304456

called 9 8008110478

[Ayodeji Okanlawon]

Mohammad,

From the logs everything looks okay except that your provider doesnt send a 183 session progress or 180 ringing before sending a 200 okay. Is this a call center you are calling?

What exactly do you get when you try to dial out? Does this affect all numbers or is it just some numbers?

[Mohammad Azzeh]

It is travel agency you can say with IVR answers your call. The problem happen to some 800 numbers not all. Other numbers working perfectly on same scenario! 

Could it be the ISP not sending proper SIP messages for this tollfree numbers? [the issue appears for sequence numbers 800811XXXX only!]

[Amit Sharawat]

Hi Mohammad,

i agree with Ayodeji, Your provider needs to send 18X response from the call, otherwise the call manager will wait for it and if it does not get it, it will drop the call because it will confuse.

[Ayodeji Okanlawon · Accepted solution]

There are a few possibilities here..

Most toll free numbers play some sort of announcement before the call is connected. It is possible that your provider needs to enable PRACK on their side and you also enable PRACK on CUCM. For this to work, your provider must send 183 with SDP and indicate request fro PRACK

So speak to your provider and explain the situation to them and find out what is going on.

[Mohammad Azzeh]

I'll do so, thanks. Please check the debug for working toll number, if you have any comments.

[Vivek Batra]

Mohammad,

Apart from excellent suggestions from my friends, would you like to change the transport type between CUCM and gateway to UDP... as its TCP here and UDP between gateway and provider. Although this should not create an issue, but for the sake of simplicity, change the outgoing transport type under SIP trunk security profile to UDP and reset the SIP trunk.

Can you also share the traces of working call to other toll free number? 

Also curious to know, are you also trying to invoke MTP for this call?

- Vivek

[Mohammad Azzeh]

Vivek here is attached the debug fro working number. I can see the right messages for the sip and the call is successful.

[Vivek Batra]

Hmm so in working call, provider is sending 18x messages as expected, however SIP provisional responses in nature are optional and that should not be a reason for CUCM to disconnect the call.

Did you try changing the transport type to UDP? I am not sure if this would work as working call is fine with the same configuration however worth to check, else you should once check with provider about the difference in signaling for working and non-working call.

- Vivek

[Mohammad Azzeh]

I'm going to change to UDP but after working hours. and will get back to you.

thanks.

[Ayodeji Okanlawon]

Can you please post the complete logs. Can you also include the ff logs

debug ccsip messages.

[Mohammad Azzeh]

see attached plz below