please explain a little if what you want to do is change the external IP adress to the router simply unplug the cable modems power for 15 min and the router do a rest on the router once you pug the modem back in and turn the power on the modem will rest itself and isue a new IP to the modem and router. example the modem will remember the mac address of the router so unless renewed the modem will hand out the same ip each time to the same router you will need to clear the modem first and un poerw all devices if you do not turn the power off the router then the modem will reisue the same IP to that modem most the time.
Most routers come with a default address, usually 10.0.0.1 or 192.168.0.1, which are addresses on network numbers reserved for private networks. These are changed routinely to match the internal numbering scheme of your network. The procedure, however, depends on the manufacturer and model of your router. There is no generic procedure for doing this. Also, there are at least two addresses on a router - the local IP address (LAN) and the remote IP address (WAN). Both need to be set correctly for the router to operate. For Internet use, the WAN interface is uaually set to use DHCP, which automatically receives its address from your service provider , but you must set the LAN interface yourself. Again, the process is specific to each device. Check the manual - you may have to download it from the manufacturer's website - or repost with more information about your router.
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