Within the folder "Router Environment" of each router is a property "routername" which contains the logical name of the router. This name must be set if multiple routers are running on one host. If this property isn't set, the routername is equal to the DNS name of the host where the router is running on.
Be aware, that changing the routername is - even in a connected router network - a very heavyweight change, because all references to this router (authentication grants, static routes etc) must also be changed. For this reason it is the very best, to give each router per default a logical routername on initial configuration. In this case, there are really minimal changes if, for example, a router is transferred on another physical host or another router is started on the same host.