Serial link.
Input errors: Gives the total number of no buffer, runts, giants, CRCs, frame, overrun, ignored, and abort counts. Other input-related errors can also increment the count, so this sum might not balance with the other counts.
Overruns: Gives the number of times that the serial receiver hardware was incapable of handing received data to a hardware buffer because the input rate exceeded the receiver's capability to handle the data.
Eth Link:
Input errors: Includes runts, giants, no buffer, CRC, frame, overrun, and ignored counts. Other input-related errors can also cause the input error count to be increased, and some datagrams may have more than one error; therefore, this sum may not balance with the sum of enumerated input error counts.
Overruns: Shows the number of times that the receiver hardware was incapable of handing received data to a hardware buffer because the input rate exceeded the receiver's capability to handle the data.
Its very much important to check for how long the errors are been occuring. You need to clear the counters for the serial or fast eth and check if these errors are on regural basis or on daily.
The input errors will incerese when there is loss in packet transmition. If this is high you may notice a degradiation in the line or interface.
below are the links for serail and eth troubleshooting.
http://www.cisco.com/en/US/docs/internetworking/troubleshooting/guide/tr1915.html
http://www.cisco.com/en/US/docs/internetworking/troubleshooting/guide/tr1904.html
Hope this is helpful...
