Hello Nigel,
While it is technically not possible to enter a specific MAC address into the RV042 for blocking purposes, you may find the following features useful. You may also refer to page 20 of the RV042 administrator guide located here: http://www.cisco.com/en/US/docs/routers/csbr/rv042/admin/guide/RV042_V10_UG_C-WEB.pdf
Block MAC address on the list with wrong IP address
To block traffic from devices with MAC addresses on the Static IP list but using the wrong IP addresses, select this option. It prevents users from changing device IP addresses without your permission.
Block MAC address not on the list
To block traffic from devices using dynamic IP addresses, select this option. It blocks all devices with MAC addresses not listed on the Static IP list.
Let me know if you find these features of the RV042 useful for what you are attempting to implement.
Thanks,
-Lindsey
