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Cisco router(s) 10/100 taking input/crc errors

I am getting input and CRC errors on the WAN interface of my Cisco router.

I have tried several Cisco routers - (3) 1841's, and now a 2801.

I've  replaced all cabling.  The Internet connection (cable) has been changed  from coax (30x5 - replaced the modem 3 times as well), to fiber at  50x50.

We've worked with ISP and changed speed/duplex to different values - both auto and "locked" to matching values.

Any  possibility the 10/100 interfaces on the 1841/2801 are having issues  with the Gbe links on all sides?  The inside interface is connected to  either a Gbe switch, or to the Gbe port on the Barracuda and does not  report input errors.

Additionally, with 50x50 service, and a  single laptop connected to the inside interface of the 1841/2801, I can  only pull about 20x50.  If I bypass the Cisco and connect directly to  the ISP gear, I can pull the full bandwidth (50x50).

One last nugget of information - this interface (fa0/1) is connected to the cable ISP, but we are using BGP and a GRE tunnel to route IP space from ISP #2, which is also connected to this router with a T1 WIC.  No NAT'ing is performed on this router - ALL  IP's are public IP's.

The current configuration is:

- Cisco ME3400 fiber switch from the ISP

- copper patch cable directly to the 2801

- both devices set to auto speed/duplex

- int s0/0/0 - T1 to ISP #2

- int fa0/0 - "inside"

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Cisco router(s) 10/100 taking input/crc errors

Post the output to the command "sh interface ".

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