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Cisco CRC Errors

Posted on 2004-08-18
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Last Modified: 2008-02-01
Have a point to point leased T1 line from NY to Florida - Cisco 3600 in NYC and a 2600 in Fl.  It is taking input and CRC errors at both ends.  Had the telco run a 2 hour stress test last night and they state the circuit is clean.  I am not seeing any packet loss or latency, just the errors themselves.  I can post configs or stats for either router if someone could help me out or advise me what else I might check.  Last week someone on this site helped me get the clocking set correctly as I was getting slip secs - that corected the issue at my other location that is connected to NYC...but not the Florida location - after monitoring I still see CRC and input errors.  They seem to be accruing more rapidly in the NY 3600 as opposed to the Fl 2600.
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Question by:mrsmileyns
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Author Comment

by:mrsmileyns
ID: 11829759
I see that this T1 is still getting slip secs in my New York router - which would indicate a clocking problem and cause the errors - but I am not sure how to fix this at this point.
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Expert Comment

by:bfarmer
ID: 11830379
Some thoughts:

1)  Did the Telco test to your equipment (on both sides)?  Or only to the Smartjack?

2)  How far is your equipment from the demarc?  You may need to adjust how hot the signal coming from the router is:

2600(config-if)#service-mod t1 lbo ?
  -15db   -15 DB
  -7.5db  -7.5 DB
  none    None


3600(config-controller)#cablelength ?
  long   long cable
  short  short cable
 
3)  Ask your Telco if they are providing clocking on the NY to FL leased line.  I'm guessing they are given the distance and what I would assume to be different LEC's.
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Author Comment

by:mrsmileyns
ID: 11830486
1.  I have to check with the telco - I know they tested on both sides...but not sure how far they went.

2.  I am not sure - In NYC we are on the 8th floor and I believe the demarc has been extended up to our server room - in that case I am only a few feet from the demarc.  I am not sure about Florida.

The NYC 3600 is set to long cable length.  I am not sure how to see how many db's the FL T1 is set to.

3.  Currently the FL T1 is set to clock source internal and NYC is set to line. I can check with my telco.

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Author Comment

by:mrsmileyns
ID: 11830547
Also - if it is worth anything - the NYC 3600 has 2 additional T1's connected to it - one is on the same card and one is on a different card - but neither of these are taking errors.  All of the extended dmarcs are the same distance from the 3600 in my server room, as far as I know.
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Expert Comment

by:bfarmer
ID: 11830744
1)  The next thing may be to ask for an end-to-end test.

     Also, do you have remote access to FL when the line is down?  If so, you can try some of your own testing by turning up a loop on one side and sending extending pings with different patterns.

2)  NYC sounds right for cable length.  The demarc is extended, but the point of entry (telco demarc) is still on the ground floor.  
     FL  the default is 0db.  This is usually fine, but you may want to bump this is you are several hundred feet from the telco demarc.

3)  I've run into both situations with leased lines, that's why its best to check with the Telco on clocking.  Reading your last question, it sounds like you've tried both options already, however...
     
     How is the NY-NJ clocking configured?  Which side is line, which side is internal?
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Author Comment

by:mrsmileyns
ID: 11830876
Talked to telco - they state they tested end to end - CSU to CSU  - they state it is clean - asked them about who is providing the clocking - they state they are not providing the clocking - however they referred to it as timing...not clocking - if that matters.

I do not have access to the FL site when the circuit is down.

For both NY-FL and NY-NJ I have the NY side as line and the remote sites as internal
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bfarmer earned 250 total points
ID: 11831079
I'm not sure how they would have tested end-to-end when they don't have access to your equipment...  [|-)

End to end means they send techs out to both sites with T-birds and test between them.

Clocking/timing  are pretty much interchangable (I'm sure somewhere there's a purist who is grimacing...)

I would try reversing your clocking.  Make NY internal on all as it is the hub site.  Set the remote sites to line.

Otherwise, NY is getting clock from both remote sites, which may be the cause of your slips.
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Author Comment

by:mrsmileyns
ID: 11831170
no - then they didn't test end to end - they state they did csu to csu

i will try reversing the clocking - i see what you are saying - it would be like a conflict
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Author Comment

by:mrsmileyns
ID: 11831315
i just reversed my clocking - all internal on the 3600 controllers - all line on the remote 2600's - I will see if anything accumulates - but nothing so far...:)
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Author Comment

by:mrsmileyns
ID: 11832243
been over an hour - all connections are being used now - not a single error or slip sec - looks good so far - thanks
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Expert Comment

by:bfarmer
ID: 11832264
Cool, glad to hear it.
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