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isdn flap ...

Posted on 2010-11-22
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Last Modified: 2012-05-10
Hi there,
was looking at an E1 link that is generating lot of CRC errors/slips. The weird thing I see about the link is when i do 'show isdn status', it shows me the following

....

 Layer 1 Status:
        ACTIVE
    Layer 2 Status:
        TEI = 0, Ces = 1, SAPI = 0, State = MULTIPLE_FRAME_ESTABLISHED
        TEI = 0, Ces = 1, SAPI = 63, State = TEI_ASSIGNED
 ...

Now, in normal circumstances you see either 'Multple_frame_established' (which means layer 2 is ok) or 'tei_assigned' (which means its not ok) but  I'm baffled why the two of them are there together ? what does that indicate. Ofcourse, the link has problems routing voice calls but am not sure what to interpret the output of above command as ? any help wud be appreciated, thnx.
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Question by:nabeel92
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SteveJ earned 2000 total points
ID: 34201384
TEI_ASSIGNED means you are not exchanging Layer 2 frames with the switch and that's probably due to the problems you are seeing on the E1 link. MULTIPLE_FRAME_ESTABLISHED just means that you received an ISDN SABME message, and have sent a UA to sync up with the switch but if you are having E1 problems you will have difficulty syncing up and never see RR frames or you will see the RR frames and then if the switch misses 4 RR frames (keep alives) it will resend the SABME frame. In other words, your ISDN line will flap.

Clean up the E1 errors. If you are on a Cisco router, do a show controllers e1 and figure out the source of the errors.

Here's a link (http://www.cisco.com/en/US/tech/tk713/tk628/technologies_tech_note09186a00801509d7.shtml) to troubleshooting "T1" ISDN on Cisco routers . . . maybe you can find the E1 equivalent or at least learn enough from this document to help you figure out where the problem is.

Good luck,
SteveJ
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