# GTP Subscriber Trace Configuration

You can configure a NetScreen device to identify and log the contents of GTP-U or GTP-C messages based on IMSI prefixes or Mobile Station-Integrated Services Data Network (MS-ISDN) identification. You can identify subscribers by their IMSI or MS-ISDN and log the content of user data and control messages going to and from the subscriber.

The NetScreen device sends the logged packets to an external server (such as Syslog) dedicated to Lawful Interception operations.

### To Configure the Subscriber Trace feature

1. Enter the following information:

Maximum Simultaneous Active Trace: Enter the number of traces that the NetScreen device can actively handle concurrently. The default value is 3 and the range is 1 to 20.

Trace Message: Specify the number of bytes of data you want the NetScreen device to log. You can log partial or complete packets. The default value is zero, which means that the NetScreen device does not log any of the content from a GTP-U packet.

Subscribers Identified by: Indicate the type of identification by which you want the NetScreen device to identify a subscriber.

ID Type: Select IMSI or MSISDN.

ID: Enter the IMSI or MSISDN number.

Action: Select Add to activate a subscriber trace or Remove to delete it.

2. Click Apply to save your settings.