according to NS9210 hardware reference manual:
the processor has controlling bits to run ethernet in promiscous mode.
A look into the Linux ethernet driver:
linux/drivers/net/ns9xxx-eth.c search for ETH_SAF_PRO shows that those bits can be set, so its implemented in the driver.
next step would be to port/cross compile tcpdump for ARM and try to run it on the NS9210, presumed the package will not be to big to run from the Connect ME 9210 flash or RAM.
If its too big, maybe you could get a "tiny" version for busybox or similar thing. see e.g.: