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Community Member

Troubleshooting Increasing CRC Errors

I have a 7206 Router with 2 Fast Ethernet Interface. From my ISP's modem a cat5e is connected to FA1/0 (WAN) and my switch is connected to FA2/0(LAN). My question is, the increasing CRC errors and Input Errors in WAN Interface (FA1/0) I know that CRC errors is on the physical layer. I tried replacing the cables and FA interface module but still no avail. I already escalate the problem with my ISP but the weird thing is they did not found any CRC errors on their side. I think the DTE modem on our side is the cause of the problem. Any suggestions?

Cisco Employee

Re: Troubleshooting Increasing CRC Errors

With ethernet, I would check the duplex settings. A duplex mismatch can lead to an increase of errors. If your interface is autonegotiating, try manually setting it to either half or full duplex (you will also need to hardcode the speed), and see if the errors stop increasing.

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