Hello everyone!

I need some help with ettercap so I described in topics to make it easy (or not) to understand the situation.

Structure:
I have a Router/Switch (Wireless too) Linksys WRT54G v.6 with DD-WRT v24-SP1 firmware on it.
The host computer is a Windows Server 2008 with VMware Workstation 6.5 and a guest S-T-D installed.

Problem:
- VMware bridged network option
When I use the '#ettercap -i eth0 -Tq -M arp // //' the host acuses duplicated ip's in the network.

Other options that gives the same result:
#ettercap -i eth0 -Tq -M arp /gateway_ip/ //
#ettercap -i eth0 -Tq -M arp // /gateway_ip/
#ettercap -i eth0 -Tq -M arp /hosts_ip/ //
#ettercap -i eth0 -Tq -M arp // /hosts_ip/

- VMware NAT network option:
Once the network is isolated from my real network, the ettercap works just fine as the virtual "nated" network works as a switch (I guess).

Questions:
1) Is it possible to ettercap ARP Spoof a router/switch or not?
2) Am I missing something here or the router "understand" that there's another "router" (as the ettercap do that forwarding the connections) in the network
   with the same ARP so it goes crazy?
3) Or Am I talking crap? :^D

Thank you very much