XBee ZNet 2.5 (formerly Series 2)

After upgrading the xbee firmware to 1241 for router/ end device, how to set a particular xbee to act as as a router or end device. Cant find any commnad or setting for that
Please guide..

There isn't a setting or command to change it; it is a completely different firmware. If you want an XBee module to be a Router or End Device, you should flash it with the 1241 firmware version. If you want the XBee module to be a Coordinator, it should be flashed with the 1041 firmware version. These version numbers refer to the "ZNet Router/End Device AT" and "ZNet Coordinator AT" function sets. I hope that helps.

EDIT: maybe I misread the question...
Once the module has the correct firmware on it, it is already configured with the default values needed to function as a Router/End device (with firmware 1241). You may need to send it the AT commands to join a particular network if you are not using the default values on your other modules. Remember that with the ZNet modules, a Coordinator must exist to form the network.