A secure shell works just like Telnet, SSH allows a user to access a device remotely to manage it. In SSH the connection between the user and the remote device is encrypted and secure including usernames and passwords.

Secure shell (SSH) is a client-server protocol, an SSH client is a PC, and an SSH server is a remote device such as a router, switch, or firewall. When we establish the connection a network admin can execute commands on the remote device which could be a route, switch, or firewall.

We know that having the talent to manage remote devices is not exactly a security best practice because of talent's lack of security. Instead, the accepted alternative to talent is a Secure shell as we discussed earlier encryption and security of SSH.

We have two versions of Secure Shell (SSH) and SSH version 2 is an IETF standard in this lab we are using SSH version 2. SSH version 1 is not secure compared with version 2. We need to set up access to the Cisco device for SSH, we need a user account on our remote device.

By default, telnet is enabled but, in a few steps, we can configure a secure shell: -

First, we must ensure that our IOS supports SSH.
Configure a hostname if you already preconfigure that is good if not then we need to configure the hostname.
Configure domain name if it preconfigures then well and good if it's not then we need to configure.
Configure client authentication.
Configure a server (router, switch, or firewall) to generate the RSA (Rivest-Shamir-Adelman) key.
Configure the SSH version.
Enable SSH on the VTY lines.

Let's see the topology: -

Topology; -

Goal: -

configure the topology as per the diagram.
configure user name cisco and password cisco321 on both SSH servers.
assign IP address to their interfaces.
configure domain name internetworks.
configure SSH key1024 bit on both SSH servers.
configure default gateway 192.168.10.1
configure VLAN interface address 192.168.10.100/24
make sure PCs get full access remotely to our router and switch.

Router(config)#hostname ROUTER_1

ROUTER_1(config)#username cisco privilege 15 password cisco321

ROUTER_1(config)#ip domain-name internetworks

ROUTER_1(config)#crypto key generate rsa

The name for the keys will be: ROUTER_1.internetworks

Choose the size of the key modulus in the range of 360 to 2048 for your

General Purpose Keys. Choosing a key modulus greater than 512 may take

a few minutes.

How many bits in the modulus [512]: 1024

% Generating 1024 bit RSA keys, keys will be non-exportable...[OK]

ROUTER_1(config)#line vty 0 4

*Mar 1 0:18:13.680: %SSH-5-ENABLED: SSH 1.99 has been enabled

ROUTER_1(config-line)#login local

ROUTER_1(config-line)#transport input ssh

ROUTER_1(config-line)#exit

ROUTER_1(config)#interface gigabitEthernet 0/0

ROUTER_1(config-if)#ip address 192.168.10.1 255.255.255.0

ROUTER_1(config-if)#no shutdown

ROUTER_1(config-if)#exit

Switch(config)#hostname SWITCH-1

SWITCH-1(config)#username cisco privilege 15 password cisco321

SWITCH-1(config)#ip domain-name internetworks

SWITCH-1(config)#crypto key generate rsa general-key modulus 1024

The name for the keys will be: SWITCH-1.internetworks

% The key modulus size is 1024 bits

% Generating 1024 bit RSA keys, keys will be non-exportable...[OK]

*Mar 1 0:26:11.185: %SSH-5-ENABLED: SSH 1.99 has been enabled

SWITCH-1(config)#line vty 0 4

SWITCH-1(config-line)#login local

SWITCH-1(config-line)#transport input all

SWITCH-1(config-line)#end

SWITCH-1(config)#interface vlan 1

SWITCH-1(config-if)#ip address 192.168.10.100 255.255.255.0

SWITCH-1(config-if)#no shutdown

SWITCH-1(config-if)#exit

SWITCH-1(config)#end

%LINK-5-CHANGED: Interface Vlan1, changed state to up

%LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan1, changed state to up

(now we need to configure IP address on our PC1)

(after clicking on X scroll down and click on Telnet/SSH client)

(after clicking on Telnet/SSH Client new window popup)

( now give the hostname or IP address which is 192.168.10.100 for switch / 192.168.10.1 for router and user name cisco for both after this give the password cisoc321)