Terminating ISDN calls return a Q.850 Cause Code when they end. We can use these codes to determine whether or not to reroute the call to another signaling group via additional configured entries in the Call Route Table. A Cause Code Reroute table contains one or more Q.850 Cause Codes which, when matched, trigger a reroute. To use a table created here, select it from the Cause Code Reroute field in a Call Routing Table entry.

Note

When there are multiple redirects of a call, the SBC operates as follows:

A redirect can be a SIP 3xx or a Cause Code Reroute. If there is a redirect of a call, all works well. If there is more than one redirect, the SBC goes back to using the original Calling and Called numbers. In the example below where the Calling number is 1234567 and the Called number is 7654321:

  • SIP 302 redirects the call to Contact: 9876543
  • the SBC sends a new INVITE to the redirected number 9876543

If this call, then, fails and is Cause Code rerouted, the SBC uses the Calling number 1234567 and the Called number 7654321 for the next attempt. 

In other words, if a redirect happens on the outbound side, the SBC redirects the call to a new number. If the call disconnects with a Cause Code in the Cause Code Reroute table (this happens when the SBC clears the call back to the inbound side), the SBC reroutes the original call, not the redirected outbound call. Hence, the SBC uses the original numbers as the Called and the Calling numbers for this call, not the redirected numbers.


Working with Cause Code Reroute Tables

  1. In the WebUI, click the Settings tab.

  2. In the left navigation pane, go to Telephony Mapping Tables > Cause Code Reroutes.

To view a profile's properties:

  1. Click the pop-up icon () next to the entry you want to view.
  2. When you are finished, close the window.

To delete an entry, select the checkbox next to the entry and then click the Delete () icon.

Creating and Modifying Cause Codes
Q.850 to SIP Reroute Mapping Table