# Troubleshooting the System

This chapter provides information and instructions for using the system command line interface (CLI) for troubleshooting any issues that may arise during system operation.

Test Commands

In the event that an issue was discovered with an installed application or line card, depending on the severity, it may be necessary to take corrective action.

The system provides several redundancy and fail-over mechanisms to address issues with application and line cards in order to minimize system downtime and data loss. These mechanisms are described below.

Using the PPP Echo-Test Command

The system provides a mechanism to verify the Point-to-Point Protocol session of a particular subscriber by sending Link Control Protocol (LCP) packets to the mobile node. This functionality can be extremely useful in determining the quality of the air link and delays that may occur.
The command has the following syntax:

    ppp echo-test { callid call_id | ipaddr ipv4_address | msid ms_id | username subscriber_name }

Keyword/Variable | Description
--- | ---
callid call_id | Specifies that the test is executed for a subscriber with a specific call identification number (callid). call_id is the specific call identification number that you wish to test.
ipaddr ip_address | Specifies that the test is executed for a subscriber with a specific IP address. ipv4_address is the specific IPV4 address that you wish to test.
msid ms_id | Specifies that the test is executed for a subscriber with a specific mobile station identification (MSID) number. ms_id is the specific mobile station identification number that you wish to test.
username subscriber_name | Specifies that the test is executed for a subscriber with a specific username. subscriber_nameis the specific username that you wish to test.

The following displays a sample of this command’s output showing a successful PPP echo-test to a subscriber named user2@aaa.

    USERNAME:
    user2@aaa   MSID: 0000012345   CALLID: 001e8481

     Tx/Rx 1/0   RTT(min/max/avg)
    0/0/0

    USERNAME:
    user2@aaa   MSID: 0000012345   CALLID: 001e8481

     Tx/Rx 1/1   RTT(min/max/avg)
    77/77/77 (COMPLETE)