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CRC errors on serial interface

CRC errors on serial interface

CRC errors on serial interface

I am getting many crc errors on my serial interface.  My interface resets frequently bringing the circuit down.  How can I perform software and hardware loopback testing on the router to see if it is the problem?  I am not at the location nor will the telco help out anymore here.  They tested clean many times so the testing is in my court now.


RE: CRC errors on serial interface

I had a similar problem and it turned out to be bad hardware(rj-45 cbl to smartjack from router eth).
CRC errors, etc..I had the
provider loopback the csu-dsu and it tested clean. After replacing the cable it went back to normal. In other words: most of the time a hardware issue.

Good Luck.

RE: CRC errors on serial interface

I disagree. Most of the times, CRCs are cuased by the telco. When the telco tells you that they have looped the circuit, they mean (in the case of a T1)they have looped the smart jack. They are unable to test all of the way through the smart jack. If they tell you that they have tested through the CSU/DSU, then I would believe a possible hardware problem.

If you have a user at the site the can unplug a cable, make up a loopback plug and send it to the site. Unplug the cable from your router and plug in the loopback. If you run clean, call the telco, plug the loopback into the smart jack and see how they run to that.

RE: CRC errors on serial interface

usually CRC and framing errors reveal a clocking problem. If you have high volume of CRC's though it's usualy a bad wire.

the fact that the link is up sometimes tells me that you can get a connection so a true to form clocking problem is not the problem. If it was you wouldn't even get the circuit up.

try using a different cable. this should help, sincec your provider tested clean.

    "Weapons are tools of destruction,
    not used by good leaders.
    When their use cannot be avoided,
    the best policy is calm restraint."


RE: CRC errors on serial interface

Just as an FYI, most smartjacks automatically go into loopback when the customer cable is disconnected.  That way, the NOC isn't flooded with alarms.

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