To change the Defualt password (in Cisco routers the defualt usename and password is cisco) on a Cisco router and Enable Telnet access to the router we need to type the following commands:
router#config t
Router(config)#enable secret mypassword
Set VTY password (Telnet)
Router(config)#line vty 0 15
Router(config-line)#login
Router(config-line)#password mypassword
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