I have voice interface NM with 2 voice port that was installed in slot#1 of my cisco 3600 router. I have to remove this voice interface NM as our company requirement and install a new FastEthernet NM with 2 WAN port. On these 2 WAN port I installed the 2 voice port from the old voice interface NM. When I power up my router and check the configuration the new FastEthernet NM was not detected by the router and the LED at the NM backplate was inactive. Only the orange lights from the voice port was on and obviously were not also active. What could be the problem? Is it possible that the new FastEthernet network module is problematic? And is it ok to install a voice-port to a WAN port?