Frame-Relay PVC Inactive

[mesagreg]

Hi folks,

I have a frame-relay pvc that was configured and working correctly for a couple of weeks. It has gone down, and the status shows inactive when I do a sh frame-relay pvc. The sh interface command reveals that the interface is down and the protocol is down.

The telco says that they can see the CSUs at both ends. The lines are terminated on a channel bank, and the company that maintains the channel bank says that their equipment is okay.

Any ideas on where to start checking? I shut down and restarted the serial interface, but no luck.

Thanks in advance,

Greg

 

[RouterGod]

"Serial0 is down, line protocol is down"

This output means you have a problem with the cable, channel service unit/data service unit (CSU/DSU), or
the serial line. You need to troubleshoot the problem with a loopback test. To do a loopback test, follow the
steps below:
Set the serial line encapsulation to HDLC and keepalive to 10 seconds. To do so, issue the commands
encapsulation hdlc and keepalive 10 under the serial interface.
1.
Place the CSU/DSU or modem in local loop mode. If the line protocol comes up when the CSU,
DSU or modem is in local loopback mode (indicated by a "line protocol is up (looped)" message), it
suggests that the problem is occurring beyond the local CSU/DSU. If the status line does not change
states, there is possibly a problem in the router, connecting cable, CSU/DSU or modem. In most
cases, the problem is with the CSU/DSU or modem.
2.
Ping your own IP address with the CSU/DSU or modem looped. There should not be any misses. An
extended ping of 0x0000 is helpful in resolving line problems since a T1 or E1 derives clock from
data and requires a transition every 8 bits. B8ZS ensures that. A heavy zero data pattern helps to
determine if the transitions are appropriately forced on the trunk. A heavy ones pattern is used to
appropriately simulate a high zero load in case there is a pair of data inverters in the path. The
alternating pattern (0x5555) represents a "typical" data pattern. If your pings fail or if you get cyclic
redundancy check (CRC) errors, a bit error rate tester (BERT) with an appropriate analyzer from the
telco is needed.
3.
When you are finished testing, make sure you return the encapsulation to Frame Relay. Regards,

Don