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HOW TO TEST A 56/64 KB LINE

TO PROVE IT'S THEM AND NOT US

This page is for the use of the Acadia Parish Library.  Neither the Acadia Parish Library nor the staff recommend using this procedure for any other institution, nor do we  imply or agree to accept any responsibility for damage to equipment or lost time due to the use of any information on this page. This procedure will work with T-1's also, and if you have Adtran TSU's, they come with a their own loopback plug.

First things first.  Are your sure everything is plugged up correctly and turned on?  Next, have you verified that the dip switches on the back of the CSU's are set correctly on both ends?

Adtran CSU Switch settings

Only one switch is set differently, but does it make a difference.  This also happened to me - once. It was us and not the telephone company.  If everything appears to be correct, then continue.

Why do you think it may be them instead of you?  Can you ping across to the other side?  To the router?  To a computer inside the other router? If you can ping the router, but not a computer inside the other lan, then the ethernet port may be administratively down.  If you can ping the router you can telnet into it.  Once into the router, do a show interface command.  When you get to the ethernet0 or (ethernet0/0 for a 2611) is it up or down?  If it is administratively down, try turning it on.  First, use the enable command.  Do a config t, then int eth0, then no shutdown, then ctrl z. Then  do a show run.  Then do another show int and see if eth0 is up.  If it is then see if you can ping into a machine inside the lan.  If that solves your problem great.  If not, keep going. Try an extended ping that is a ping /t.  If it still looks OK, send a larger packet with ping /t /l 1000 192.168.whatever.  For a list of ping commands, at a Dos or Command prompt type ping /?.  To end an extended ping hold down ctrl and press c.  If no time outs or lost packets are shown, you may not have a problem, but if you think you do keep reading.  Your problem may be sporadic and you will need to test for an extended period  to verify that your equipment is good.  Several signs of a line problem are the inability to log into your circ server, the inability to download files, and the buttons on web pages never seem to load.

Telnet into your router and do a show int command.  Is your line up?  Do you show a lot of errors? Do you show a lot of CRC and Frame errors?  A lot of errors is over 1% of total data received.  Do you see a lot of carrier transitions?  If you cannot download and if the buttons on web pages do not appear, you will have a lot of errors.  When was the last time the registers were cleared?

Before you can begin the testing process  you need a  loopback plug  for a 64/56 kb line.  It looks like the following picture.

You have to make it yourself.  The picture should explain how it is done.  You can make four loopback plugs from one six inch piece of cat5 wire.  When you are making them, make at least two, one for each end of the problem line.  When you have them finished, go somewhere and buy at least two (2)  cat5 connectors.  (You usually use cat5connectors  to make two short patch cords into a longer patch cord, but we use them to connect the loopback plug to connect to the gray cord going from the CSU to the telephone company plug.)   When you've got this done, go and unplug your your gray line from the telephone company connection and plug the cable into your loopback tester. 

You actually need to do this on both ends:  at your main router and at the branch with the problem.  This will isolate your equipment for testing purposes.  Once your cable is connected, telnet into your router.  Enable your router and then do a clear counter command.  You will be asked to confirm this decision.  Hit either the  y or enter  key.  Hitting the N key cancels the command.  If you want to just clear the serial counter, do clear counter ser0 (clear counter ser0/0 or clear counter ser0/1 on the 2611 etc.) enter, then y or enter.  Once your counters are clear, log out of the router; exit works.  Now go to a computer and  extend ping command with a large packet such as ping /t /l 3200 192.168.?.?.   The ping to IP address should be either the router or a machine behind the router on the other end of the line you are testing.  You can actually run multiple machines or multiple pings with the same machine to the same address.  This really speeds up the amount of data being sent.  You also need to do this same testing process on the other end and then try to ping back to this end.  After a few minutes log back into the router and do a  show int  command.  You should see that the line is looped and no errors.  If you see errors, it may be you and not them.  If you don't see errors then it is probably them.  You can let this ping process run all night, then copy and paste and print the show int results and then, if you don't show any errors,  you can speak with authority that your equipment is not the problem.  The beauty of this system is that you have tested from the very beginning of your equipment through your system on both ends.  Before you call the telephone company, clear your counters again and let your system run for another 24 hours.  Record the day and time of the reset of your counters.  You may want to telnet into your router every couple of hours and try to determine when the problem occurs.  When you notice a problem, print out the show int information and record the date and  time.  If you can identify a specific time that the problem occurs, it  will help the telephone company identify the problem.  The problem  may be due to many things.  Vibrations caused by a myriad of actions can cause a line to short as can a temperature change of a few degrees.  Obviously, there are other associated reasons for such occurrences, but knowing the time truly helps.  Most of the time when the telephone company checks a line, it is a very quick test for a short period of time.  Sometimes they need to do an extended stress test to identify the problem.  The information you provide will help convince them to do an extended test.

Of course there is always the possibility  that the line is good;  it is just connected to someone else's router.  Don't laugh.  I had that happen in April of 2002.  I could telnet into someone else's system.  That is scary,  because that meant they could do the same to me.  

If you have any questions, feel free to contact Lyle at 337-788-1880 or e-mail me at the address below.