Loopback for Testing

To perform loopback on a VDAC-ONE card in a lab environment, specify the same source and destination IP addresses in a Route Control (or Outseize Control) message. The source and destination RTP port numbers must be different.

To set up a VoIP call using the same IP address, send Route Control/Outseize Control messages to the same IP address with different port numbers. There are 40 channels per module, so you can establish up to 20 pairs of end-to-end calls per IP address. If you try to re-use a port number for a channel that is already being used for a call (RTP, RTCP, T.38) you receive the following error message:

0x4B: RTP Port in Use.

Example:

Route Control/Outseize Control Message 1:

• Source IP Address: A

• Source Port Number: 1000

• Destination IP Address: A

• Destination Port Number: 1004

Route Control/Outseize Control Message 2:

• Source IP Address: A

• Source Port Number: 1004

• Destination IP Address: A

• Destination Port Number: 1000

The call is now established.