I will need to upgrade the Cisco IOS on the above-mentioned Cisco router 3640 so that I can use it as a VPN gateway for a project. I already obtained the instructions involved from Cisco's website site. However, when I change the configuration register from 0x2102 to0x2101 and reboot the router, the router does not go into RxBoot Mode. ie.router(boot)>. I have a Cisco router 2503 at home which uses the same Cisco IOS upgrade instructions as the Cisco router 3620 and when it is put into RxBoot mode, it displays this prompt i.e.router(boot)> were 'router' is the name of the router after changing the configuration register to 0x2101 and rebooting the router. The Cisco instructions also states that you cannot upgrade the Cisco IOS on the router in priviledged mode i.e.router#. Any answers will be greatly appreciated.