It doesn't even have to be on the router, just the same network segment plus some ARP spoofing tricks (assuming your switch doesn't have ARP spoofing protections or they haven't been enabled) could be enough to MitM a connection.
It doesn't even have to be on the router, just the same network segment plus some ARP spoofing tricks (assuming your switch doesn't have ARP spoofing protections or they haven't been enabled) could be enough to MitM a connection.