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Point to Point T1 looping

Posted on 2003-10-21
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Last Modified: 2013-11-30
Hello.  I am trying to set up a Verizon point to  point T1 between two of our buildings.  We currently have a Frame-relay connection that we installed due to the fact that we were planning to connect three buildings together.  We have consolidated our staff into two buildings so we decided that a Point to point T1 is the more cost effective way to connect.

The issue that I have is that whenever I connect the new circuit to our Cisco routers, the routers say that the circuit is looping.  This should be a very simple process as I am using the same equipment that to working fine with the Frame-relay.  I remove the Frame-relay encapsulation from each end and the routers default the HDLC encapsulation.  The circuit then starts looping (all packets that go out come right back).  Verizon can find nothing in their configuration of the line that would be causing this problem.

Do you have a suggestions as to where I might be going wrong with the router config?  I am just removing the frame-relay encapsulation and setting the IP address of the interface on each end.

Thanks for any help that you can provide.

Charles E. Moncrief
CEM Computer Service
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Question by:cemtech
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by:NicBrey
ID: 9591424
Are you sure Verizon do not have a loop on the link. Contact them and ask to remove.
It happens all the time that ISP's test a line and forget to take the loop off...
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by:scraig84
ID: 9591913
External or internal CSU/DSU's?  Are you certian they are not configured with loop currently?  What is the message you are getting from the routers telling you about the loop?
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Author Comment

by:cemtech
ID: 9595246
Verizon says that there is no loop in the circuit, but I do not really believe them.  After my 4th complaint, their techs came out and completely rebuilt the circuit at both ends with new cards on each end and in the central office.  Both ends say that they are looped.

The main router uses an external AdTran DSU/CSU connected to the serial port of the 3800 series router which the other end has a T1 card installed in the router.  When I do a show interface on the serial interfaces, the first line on the main router says that the Serial0 is up, Line Protocol is up (looped).  On the remote router, it says Serial0/0 is up, Line Protocol is up (looped).  While the Frame-relay is set, the messages say nothing about being looped.

Thanks for you help.  I really need to get this new line up and running as the Frame costs significantly more than the Point-to-point T1.
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mburdick earned 250 total points
ID: 9595942
Check in the configuration of both routers for settings that have put the interfaces into loopback mode. If you don't find anything there, check the WIC-1DSU card on the "remote" router to make sure that the switch on the back isn't configured to loop the circuit.

Try connecting only one router at a time. What happens with the serial interface? If it's showing looped, there's a problem with Verizon. Period. Have them verify not only the local loop portion of each circuit, but make sure that the *service* isn't looped.
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by:scraig84
scraig84 earned 150 total points
ID: 9598364
If mburdick's test shows the problem is on your end and you are sure that your equipment is configured correctly, remember that a loop can be anywhere so there could be a problem with inside wiring.  Is there any chance you can get to the demarc in each building?  If so, you could bring the router down to the demarc and plug right in to the NIU (smartjack - assuming there is one).  If you plug in at the demarc and the problem goes away, that could indicate that you have faulty wiring from the demarc to your router location.

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Author Comment

by:cemtech
ID: 9598450
When I connect only the main router to the circuit, it does say that it is looped.  What should I say to Verizon to make them understand that there is a problem with their circuit.  I tried to tell them everything that I have written here and they insist that there is not a loop in the circuit.

The equipment that I am moving to the Point-to-point T1 is the exact same equipment that is working properly with the current frame-relay circuit.  I have told Verizon that also and they insist that they do not have a problem.

Thanks for the help.  I will keep bugging Verizon.
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by:mburdick
mburdick earned 250 total points
ID: 9598491
scraig84 makes an excellent point - I had a problem in the past with a DS-3 circuit not showing loop on the router, but serial packet debugs showed that I was only getting my packets back. Turned out that the DS-X was a "new" style with the connectors being in different places. I had to pull the cover to learn that I had my router connected back to itself...

Ask Verizon to run tests on the circuit to loop up each end. Also, ask them to loop all the way to your equipment. If they can't see your router on the line, then the problem is either their circuit or wiring at your end. Check for any light changes on the smart jack when you connect your router to it as well.
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by:ShineOn
ShineOn earned 100 total points
ID: 9600101
If the premise wiring has been verified, then it seems to me that it would be a configuration issue if you are using the exact same equipment and just swapping connections.  If Verizon is getting clear loopback to the smart jacks, and the premise wiring checks out, and the mburdick test comes up with the same results, that has to be the answer.

Have you double-checked the frame type on the new circuit?  Is it the same encoding as the Frame Relay T1?  (I forget the alphabet-soup for the T1 frame encoding types off the top of my head)

When you reconfigure the T1 interfaces for point-to-point, are you getting green lights, no status messages, on the adtran?  Can you get Verizon to send a tech to verify your TSU configuration is correct for the point-to-point?  Is the T1 NIC a model that handles both frame and point-to-point?  Are you also reconfiguring the route not to go through the frame network?  Just want to be sure you're covering all your bases...
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by:cemtech
ID: 9608160
Verizon finally found a wiring problem in their central office and once they corrected that, everything is just fine.

Thanks for all your help in confirming the problem.
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by:mburdick
ID: 9613489
On a 500-point question, I would have expected you to at least point-split this....
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by:ShineOn
ID: 9614769
The answer you accepted didn't really come all that close to the solution, either, IMHO.
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by:cemtech
ID: 9637848
I know.  I did not understand how to do the points and I was trying to split the points and it did not work.  Is there a way that I can fix it??
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by:qwaletee
ID: 9637979
Post a zero-piint queston in community support, giving teh URL of thsi question.  A moderator will help you out.
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by:ShineOn
ID: 9638192
Back on topic - this just goes to show that even when a "telco" says something is as it is, you have to keep badgering them and disproving their theories until *you* are sure they are not at fault.  

Too often in my experience, the "telco" (I say "telco" 'cause I remember when everything was AT&T) will not 'fess up to any responsibility unless you have covered every base twice to prove it is not your problem.  This is unfortunate.

It's kinda like when the old Pont-To-Point Leased Lines were popular.  You'd call with a problem connecting to a remote site.  They would "loop test" the circuit and find no problems.  After the "loop test" everything magically works again.

I swear there's some cultural dynamic that still pervades all of the telecom entities of "always blame the customer, unless you get caught."  This is too bad, and I wish the telecom industry would change their collective attitude.
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by:qwaletee
ID: 9638338
I don't blame them so much.  As a computer geek, I've been caught many times teling customers what I thought to be true -- that it was this or that guy's other process taht was to blame for an error or incorrect result -- when as it turned out, it was either all my fault, shared responsibility, or even a third party.

You examine, you analyze, you try to debug using the incomplete and imperfect data you have, and oftentimes, you arrive at the wrong conclusion despite best efforts and talent.  And, since unit tests are less likely to find probelms than system tests, and you can't always test the coplete system, you frequently find nothing wrong at your end.

The telco guys have the same problem.
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by:ShineOn
ID: 9638658
No matter what you say, qwaletee, I will always remain skeptical of the accuracy (and veracity) of what a Telco tells me.  I have had too many "telco fixes" of comm issues not to be - where all they do is a "circuit test" and voila! there's no problem.  
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by:NicBrey
ID: 9640332
Agree with ShineOn here. This is obiously a case where the Telco company did not do a proper test/troublshooting on their side. Like cemtech said: "Verizon finally found a wiring problem in their central office and once they corrected that, everything is just fine."

How many days was it since the first call was logged untill they found the wiring problem on their network. My experience is also that you have to ask them and ask them and then ask them again. This case was so obvious from the description that there is a loop somewhere, yet it took so long to resolve. They always assume the problem is on your network/routers and always look at their equipment last. In their defence though, one have to undestand that if they do not make sure that the customer's equipment is not the problem, and send out technicians for every call logged,  they would probably have to increase their rates to pay for the extra techs. they have to employ....
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by:mburdick
ID: 9641101
I, too, agree with ShineOn. I can't count how many problems that have 'magically' disappeared after they run line tests.

In my opinion, there's one word that sums up the reasons that the TELCO is so hard to work with - UNION. 'Nuff said.
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by:cemtech
ID: 9646977
I would like to thank all of you for the help.  I am new at this so how do I do a point split to give more that one person credit?
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by:mburdick
ID: 9647070
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