Frequent ie0: No carrier messages

[Spencer Kantor]

We have an old Sun 3/160 server that's running 3.2 and supporting 8
diskless 3/50's.  Over the last couple of weeks we've been getting a
frequent "ie0: No carrier" message printed to the console.  Despite the
frequency of the message (several times per hour) the system appears to be
running fine.  All cable connections are solid, network services are
running fine (as far as we can tell) and there have been no complaints
from the owners of the diskless clients about service interruptions.  We'd
like to know what causes generation of this message and what corrective
actions may be warranted.  Thanks.