System information

Troubleshooting ATM Switching Environments 21-445
ATM Switching: Frame Relay Port Does Not Come Up
ATM Switching: Frame Relay Port Does Not Come Up
Symptom: A Frame Relay port on a LightStream 2020 ATM switch does not come up properly.
Data cannot be transmitted out the port.
Table 21-5 outlines the problems that might cause this symptom and describes solutions to those
problems.
Table 21-5 ATM Switching: Frame Relay Port Does Not Come Up
Framing type mismatch
Step 1 Check to see whether both ends of the trunk are configured to use the
same framing type (PLCP, HEC, or G.804). Enter the show port
command. If there is a mismatch, the display for both ports will
indicate “DS3 other failure.”
Step 2 Change the framing type on one of the ports, as appropriate, using
the set port c.p characteristics framing type {plcp | t3-hec |
q-804} command.
Cell payload scrambling mismatch If there is a cell payload scrambling mismatch, the trunk-up-down (TUD)
protocol will fail because the payload of the cells is scrambled at one end and
not unscrambled at the other end. The trunks will never come up. However,
packets will appear to be received and transmitted without error in the port
statistics display.
Step 1 Check to see whether one end of a trunk has cell payload scrambling
enabled and the other end has cell payload scrambling disabled. Use
the show port c.p physical command to verify the status of the
payload scrambling.
Step 2 Reconfigure the trunk ports using the set port c.p characteristics
cell-scrambling {enable | disable} command so that cell payload
scrambling is either enabled or disabled on both ends of the trunk.
Telephone company network
problem
Isolate the problem by running the loopback tests described in the section
“Performing Loopback Tests” earlier in this chapter. If you determine that the
problem is occurring in the telephone company network, contact your carrier
to solve the problem.
Hardware or cabling problem
Step 1 Check all cabling and connections to make sure there are no worn
cables or loose connections.
Step 2 Make sure that cable lengths are within specification and that the
cable length port attribute is properly configured. Use the set port
c.p characteristics cable len length command to change the cable
length attribute.
Step 3 Check all hardware for problems. For more information on
troubleshooting hardware, refer to Chapter 3, “Troubleshooting
Hardware and Booting Problems.”
Possible Problem Solution