[c-nsp] EOBC0/0 ifInErrors

[Tim Rayner]

Eugene Grosbein wrote on 12/10/2020 20:28:
> It seems so:
[...]
>    Tx Errors/State:
>     One Collision Error   = 306656       More Collisions       = 1209541
[...]
>     Input Errors           = 28517
>     Output Drops          = 0            Giants/Runts          = 0/28517

> uh, obviously collisions are a transmit phenomenon, but you're seeing rx
> errors, so this isn't collisions.  I don't know what the root cause is
> here, but runts are not good on ethernet and usually indicate physical
> cabling problems.  As the EOBC interface is "cabled" via the crossbar at
> the rear of the chassis, there are relatively few failure points.

> Nick

One possibility that springs to mind here is a duplex mis-match.  If the EOBC0/0 interface that you're seeing runts on is running as full duplex, and the interface that it connects to is running at half duplex, then the half-duplex interface will record a collision and stop transmitting when it receives a frame overlapping with one that it is transmitting.  Your full-duplex interface will only see the part of that frame that is transmitted before the collision is detected - which the full-duplex interface may record as a runt.

It would be interesting to know what happens to the runt and collision stats if you can force both ends to full duplex, or both ends to half duplex.

Tim