Depends how you are connecting to the router:
Connecting via console:
Router(config)#line con 0
Router(config-line)#password 1234
Connecting via telnet:
Router(config)#line vty 0 4
Router(config-line)#password 12345
Connecting via aux:
Router(config)#line aux 0
Router(config-line)#password 12345
I haven't worked with the 1700 series, but I have worked with that version ios, so these should work.