around radius - printers, ip phones and others

Hi, What do you suggest to do with printers, ip phones and other network devices wchich can not support 802.1x ? What are you doing to secure this backdoor? One idea is to identify such devices by MAC but I think it should be something else - cause someone can disconnect fi printer - change mac addres on pc on the same as printer and welcome home :). any suggestions? Bartosz Chodzinski.