System information

Troubleshooting ATM Switching Environments 21-441

Troubleshooting ATM Switching Environments

This section presents troubleshooting information for connectivity and performance problems in

ATM switching environments. The chapter begins with general information about checking ports,

performing loopback tests, and using the ping command on a LightStream 2020 ATM switch.

The remaining sections describe speciﬁc ATM switching symptoms, the problems that are likely to

cause each symptom, and the solutions to those problems.

• ATM Switching: Trunk Does Not Come Up

• ATM Switching: Frame Relay Port Does Not Come Up

• ATM Switching: Virtual Circuit Fails to Be Created

• ATM Switching: Partial Data Delivered over Virtual Circuit

Basic Port Checks

The following steps outline the procedure for performing basic port checks. It is important to

perform basic port checks to verify that a LightStream 2020 port is enabled and functioning

correctly:

Step 1 Use the show port port-number all command to display information about a port.

Step 2 Check the Admin Status ﬁeld to make sure that the port is up.

Step 3 Check for excessive line errors, packet drops, or a lack of receive data. If there is no

receive data or if the error rate on the receive data is excessive, check the hardware,

cabling, and other physical layer components.

For more information on troubleshooting hardware, refer to Chapter 3, “Troubleshooting

Hardware and Booting Problems.”

Step 4 If the port is directly connected to a host, ensure that one side of the connection is

conﬁgured as data communications equipment (DCE) and the other side is conﬁgured as

data circuit-terminating equipment (DTE).

If two ports are connected through a channel service unit (CSU), ensure that the ports on

both sides of the connection are conﬁgured as DTE.

Step 5 If you are working with a low-speed line card (LSC) port, check the bit rate. Refer to the

section “Checking Bit Rates” later in this chapter.

Step 6 If you are working with a medium-speed line card (MSC) port, check for mismatches in

port conﬁguration attributes such as cell payload scrambling, line type, and cable length.