Description

This article describes how to enable logging for a GTP profile on a Juniper device. GTP profile logging helps identify whether GTP packets are forwarded or dropped and provides the reason for the action. These logs are useful when troubleshooting GTP control plane and user plane traffic.

 

Configure the required logging options under the GTP profile as shown below:

set security gprs gtp profile gtp1 log forwarded detail
set security gprs gtp profile gtp1 log state-invalid detail
set security gprs gtp profile gtp1 log prohibited detail
set security gprs gtp profile gtp1 log gtp-u all
set security gprs gtp profile gtp1 log gtp-u dropped

Logging Options

CommandDescription
log forwarded detailLogs GTP packets that pass inspection and are forwarded.
log state-invalid detailLogs GTP packets dropped because they failed stateful inspection or sanity checks.
log prohibited detailLogs GTP packets dropped because they failed message length, message type, or IMSI prefix validation.
log gtp-u allLogs all GTP-U packets processed by the device.
log gtp-u droppedLogs only GTP-U packets that are dropped.

Symptoms

GTP traffic is being dropped or not behaving as expected, and additional logging is required to determine the reason for packet forwarding or packet drops.

Solution

After enabling GTP profile logging, the device generates log messages that indicate GTP tunnel creation, deletion, updates, packet forwarding, and packet drops.

The following are examples of log messages:

RT_GTP_UPDATE_USER_TUNNEL_V1: update gtpv1 user tunnel, nsapi 5 from sgsn 10.0.0.1/000131ef ggsn 1.1.1.1/9462bc13 to sgsn 20.0.0.1/0000b311 ggsn 113.187.3.73/9462bc13

This log indicates that an existing GTPv1 user tunnel was successfully updated.

RT_GTP_V1_TNL_DELETE_PDP: gtpv1 message delete user tunnel successfully, teardown:0x40, nsapi(5), control tunnel(10.0.0.1/0x1d033c58 -> 1.1.1.1/0x7250b8e2)

This log confirms that a GTPv1 PDP context (user tunnel) was successfully deleted.

RT_GTP_V1_TNL_CREATE_PDP: create gtpv1 primary user tunnel(10.0.0.1/0x00019331 -> 1.1.1.1/0x94711385, nsapi(5/5)) successfully, control tunnel(10.0.0.1/0x1d033c58 -> 1.1.1.1/0x7250b8e2)

This log confirms that a new GTPv1 primary PDP context (user tunnel) was successfully created.

These log messages can be monitored using the system log to verify GTP tunnel establishment, updates, deletions, and to identify the reasons for GTP packet drops during troubleshooting.

Modification History

2025-09-03 : Article Created