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Knowledge Base

TE40 - Calls with H323 protocol not working.When receive a call with H323 protocol from the Cisco system, the incoming call screen opens on the TE40, when you answer the call is disconnected but still continues to ring

Publication Date:  2019-05-27  |   Views:  430  |   Downloads:  0  |   Author:  m84089093  |   Document ID:  EKB1100015925


Issue Description

Customer reported an issue where when he is using H323 with CISCO SX20 but also if he calls in H323 between teo TE40, the system rings and gives the notification of the call (accept or decline) but after the call is accepted nothing is working.

Handling Process

We have decided to perform a remote session where the following operations where performed:

Operations performed:


-          Made a call in SIP from TE40 to CISCO endpoint (Worked just fine)

-          Made a call in H323 from TE40 to CISCO endpoint (Worked just fine)

-          Made a call in H323 from CISCO to TE40 (The notification appears on the TE40, the end user accepts the call however after some seconds the notification appears that “The called site has rejected your call”

-          Customer told us that the CISCO endpoint has this issue when making other calls in H323

-          After  checking the signaling diagnostics it shows that the TE40 accepts the call but CISCO did not send H245 message to TE40 exchange capability and open media channel.

-          Advised customer to check also the issue on CISCO side (H323 communication)

-          At the end we have performed another test between two TE40 by placing a P2P call in h323 and the issue has been reproduced again (TE accepts the call and then there is a message saying that the called party has rejected the call due to timeout)

-          Made signaling diagnostics at the same time on both endpoints and reproduced the issue

-          Gathered debug logs on both endpoints

-          Advised customer to send us the data for further analysis

Root Cause

We have looked over the gathered signaling diagnostics during the remote session and could find that the call is dropped because of the TCP connection that is not being established. This TCP channel needs to be established because of the H245 needed to exchange capability and open media channel.

After the h225 Call Setup is sent in order to establish a connection with a H323 terminal is trying to establish a TCP three way handshake with 91.X.X.X but it fails and as such it instructs to release the call with a destination reject reason

We would recommend to check the network in order to see why the TCP connection from port 1329 -> IP address 91.X.X.X port 1324 cannot be established.


The solution for this issue was implemented by customer after our recommendation sent to check the network environment. They have modified their firewall configuration and they confirm that a call between teo TE40 in H323 can connect withou any issues. They still have an issue with callls with CISCO SX20 in H323 mode however customer will need to conduct further testing with CISCO and check from their side.