1. Change the Router default hostname

For our first lab, we will keep things very basic. We have two routers, and we need to change the default hostnames.

First router

Switch to Privileged EXEC mode
At first we need to switch from User EXEC Mode to Privileged EXEC Mode. Before Switching to Privileged EXEC CLI should look like:
```
Router>
```
To Enable the Privileged EXEC Mode We need to type enable and press enter.
```
Router>enable
```
After this the CLI should look like:
```
Router#
```
Switch to Global Configuration mode
In this mode we can not modify the configuration of the routers. So we need to switch to Global Configuration mode.
```
Router#configure termonal
```
After this the CLI should look like:
```
Router(config)#
```
To change the Router default hostname to R1
```
 Router(config)#hostname R1
```
After this , the CLI should look like:
```
 R1(config)#
```
To Exit the Configuration mode.
```
R1(config)#end
```
Then save this configuration to startup-config
```
R1#write memory
```

Complete Command Sequence

Router>enable
Router#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#hostname R1
R1(config)#end
R1#
%SYS-5-CONFIG_I: Configured from console by console

R1#write memory
Building configuration...
[OK]

Second router

Router>enable
Router#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#hostname R2
R2(config)#end
R2#
%SYS-5-CONFIG_I: Configured from console by console

R2#write memory
Building configuration...
[OK]

I used Cisco Packet Tracer to complete this lab.