What are the reasons for CRC errors in Cisco 2651 serial port ?

[kaustavcisco]

Hi,

We have a CISCO 2651 multihomed to 2 different ISP 's for Internet access. We find that the Serial 0/1 of bandwidth 256 Kbps of the WIC -2T shows CRC errors constantly increasing with the reliability decreasing. The Service provider says that testing to our modem end has no errors. The other Serial 0/0 connected to another ISP has bandwidth of 1 Mbps has no CRC errors.

What can be the possible reasons for the CRC errors ?

Pls advice

Regds/-

Kast

[m.prouty]

CRC errors are almost always cables. I would start with troubleshooting the cables. They may test fine but once they are on the router interface the CRCs start to climb. Try a few different cables and see if you see any difference in the rate the CRCs increment. If you do you have a cable problem you will need to identify if the cables connects are the problems, cable sheilding, etc. The interface itself might be faulty but if you are almost always in an UP/UP situation then look at the cables.

[vkostic]

Hi,

these CRC Errors are mostly caused by damaged cable/wires.

Change it and look what happens.

regards

Kost

[kmuthukamu]

check for the flg. things

+ Check the cables for damage.

+ Verify the correct cables are being used for the appropriate access card.

[MickPhelps]

If the cables have checked out, do a show controller and look for slip seconds. This is when the timing is drifting.

When you connect to 2 different devices and they supply timing, the router will sync up to one and drift on the other. External CSU/DSU or you supplying clocking (needs to be coordinated through telco) can fix this.

Mick.