There are four steps required to enable SSH support on an IOS router:

1- Configure the hostname command.

2- Configure the DNS domain.

3- Generate the SSH key to be used.

4- Enable SSH transport support for the virtual type terminal (vtys).

example:

!--- Step 1: Configure the hostname if you have not previously done so.
hostname carter
!--- The aaa new-model command causes the local username and password on the router
!--- to be used in the absence of other AAA statements.
aaa new-model
username cisco password 0 cisco
!--- Step 2: Configure the DNS domain of the router.
ip domain-name rtp.cisco.com
!--- Step 3: Generate an SSH key to be used with SSH.
cry key generate rsa
ip ssh time-out 60
ip ssh authentication-retries 2
!--- Step 4: By default the vtys' transport is Telnet. In this case,
!--- Telnet is disabled and only SSH is supported.
line vty 0 4
transport input SSH
!--- Instead of aaa new-model, you can use the login local command.