Cisco Collaboration Blog by Dmytro Benda: April 2022

Welcome Message

Welcome to my blog about Cisco Collaboration, voice, and contact center technologies.

I’m Dmytro Benda, a Cisco instructor (CCSI#33268) and collaboration specialist. Here I share practical articles, lab notes, configuration tips, and troubleshooting ideas based on real work with Cisco Unified Communications Manager, Unified CME, gateways, CUBE, and contact center solutions.

This blog is for engineers, students, and anyone working with Cisco collaboration technologies who wants clear technical content and real-world examples. I also post updates about Cisco training, my own courses, and upcoming learning activities.

If you have a question related to a post, a technology covered here, or Cisco training, feel free to get in touch.

Wednesday, April 13, 2022

Soure Port 5060 on Cisco CUBE for your SIP trunk connection to an ITSP

Recently, one of our students encountered a problem when connecting his CUCM to a telephony provider (ITSP) via a SIP trunk. Between the CUCM and the ITSP, a CUBE gateway was installed, as expected. The problem was the following: when making an outgoing call to the ITSP, CUBE sent a SIP INVITE, however, the provider did not respond to this request in any way, and no response messages were received from it.

Of course, the first thing to do in such a situation is to check which transport layer protocol (TCP or UDP) is configured on the gateway. However, in this case, the ITSP requested SIP messages to be sent with UDP transport, but Cisco gateways by default send all SIP messages with UDP, i.e. this was not the cause of the problem (you can control it with debug ccsip messages command). After talking with the provider's engineer, it was found out that they expect communication to the SIP gateway with the Destination Port = 5060, but they would also like to see Source Port as 5060 as well.