Switchport mode dynamic desirable meaning and usage
Switchport mode dynamic desirable is configured by default on all the Cisco switches. When someone buys a new switch from the market, they will find this mode configured for all the switchports on the switch.
The following image shows the default mode of all the switchports on the switch.
Dynamic desirable mode allows the switch to convert the switchport to either access or trunk according to the device connected to the switchport.
If endpoints are connected to the switchport then the dynamic port will act as an access port or if another switch is connected then the port will act as a Trunk port.
Although dynamic desirable mode makes our work easier as it automatically works as per the connected device, it poses a security threat to the network because anyone in the company can connect their network device to the switch and then the switch will communicate with the device by establishing an appropriate connection and this poses a security threat on the production network.
When we connect two switches that are configured as dynamic desirable then both switches will have a trunk connection between them automatically.
We can check the interface details to see the status of the interface connecting to the switch using the below command.
Show interface FastEthernet 0/1 switchport
In the output of the command, we can see the switchport configuration of this particular interface.
The status of the interface is enabled, it will show as disabled if the switchport is disabled.
Administrative mode is dynamic desirable because we have not changed the default mode.
The operation mode is a trunk, as this port is connecting to the other switch; this port automatically establishes the trunk connection with the other switch.
The trunking encapsulation protocol configured on that port can be seen.
In the same way, if we connect this port to the end device then automatically the operation mode of this switchport will change to access mode.
Dynamically switch will change its mode when connected to different devices in the network.
