ifstat.mac.rrd question

[McGraw, Robert P]

I am getting this error message in my rrd-data.log about every minute. I looked in the archive about this and only found one entry that did not provide much help. 

Also in the trends in the network traffic graph I see an interface named "mac".

2010-02-15 08:41:35 RRD error updating /local/xymon/data/rrd/gauss.math.purdue.edu/ifstat.mac.rrd from 128.210.3.205: /local/xymon/data/rrd/gauss.math.purdue.edu/ifstat.mac.rrd: illegal attempt to update using time 1266241295 when last update time is 1266241295 (minimum one second step)

QUESTION:

1) what is the "mac" interface?

2) what is causing the above error and how can I prevent this?

Thanks

Robert

_____________________________________________________________________
Robert P. McGraw, Jr.
Manager, Computer System                    EMAIL: rmcgraw at purdue.edu
Purdue University                            ROOM: MATH-807
Department of Mathematics                   PHONE: (765) 494-6055
150 N. University Street                      
West Lafayette, IN 47907-2067