Version 7.2 533 Mediant 500L Gateway & E-SBC
User's Manual 24. Routing
A release cause code indicates that the IP-to-Tel call has been rejected or disconnected on
the Tel side. The release cause codes are configured in the Reasons for IP-to-Tel
Alternative Routing table. For example, you can configure alternative IP-to-Tel routing for
scenarios where the initial Tel destination is busy and a Q.931 Cause Code No. 17 is
received (or for other call releases that issue the default Cause Code No. 3).
You can configure a default release cause code that the device issues itself upon the
following scenarios:
The device initiates a call release whose cause is unknown.
No free channels (i.e., busy) in the Trunk Group.
No appropriate routing rule located in the IP-to-Tel Routing table.
Phone number is not located in the IP-to-Tel Routing table.
The default release code is Cause Code No. 3 (No Route to Destination). You can change
the default code as follows:
To change the default Q.931 release code:
1. Open the Gateway Advanced Settings page (Setup menu > Signaling & Media tab >
Gateway folder > Gateway Advanced Settings).
2. In the 'Default Release Cause' field, enter the release cause code:
Figure 24-11: Configuring Default Q.931 Release Cause Code
3. Click Apply.
Note:
• If a Trunk is disconnected or not synchronized, the device issues itself the internal
Cause Code No. 27. This cause code is mapped (by default) to SIP 502.
• The default release cause is described in the Q.931 notation and translated to
corresponding SIP 40x or 50x values (e.g., Cause Code No. 3 to SIP 404, and
Cause Code No. 34 to SIP 503).
• For analog interfaces: For information on mapping PSTN release causes to SIP
responses, see PSTN Release Cause to SIP Response Mapping.
• For mapping SIP-to-Q.931 and Q.931-to-SIP release causes, see Configuring
Release Cause Mapping on page 555.
The following procedure describes how to configure alternative routing reasons for IP-to-
Tel calls through the Web interface. You can also configure it through ini file
(AltRouteCauseIP2Tel) or CLI (configure voip > gateway routing alt-route-cause-ip2tel).
To configure alternative Trunk Group routing based on Q.931 cause codes:
1. Open the Proxy & Registration page (Setup menu > Signaling & Media tab > SIP
Definitions folder > Proxy & Registration).
2. From the 'Redundant Routing Mode' drop-down list, select Routing Table so that the
device uses the IP-to-Tel Routing table for alternative routing:
Figure 24-12: Enabling Alternative Routing based on SIP Responses
3. Open the IP-to-Tel Routing table, and then configure alternative routing rules with the
same call matching characteristics as the "main" routing rule, but with different Trunk
Group destinations.
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