CCNA 200 - 301 - Lesson 60: Understanding Trunk Ports | Configuration
Section - 13: Learn How to Configure and Verify Interswitch Connectivity
Lesson 60: Understanding Trunk Ports | Configuration
We are back again with a new concept in our free CCNA course series. In this video, we will discuss what trunk ports are.
Previously in the Access Port configuration concept, we have learned how to make communication possible between VLAN10 & VLAN20 by using 2 links between switches one of VLAN10 and the other one for VLAN20.
So, using the same topology again you’ll learn that how you can use the Trunk Port to solve the problem in few steps given below:
Step 1: Take two switches (Switch1 & Switch2) and four computers (Computer1, Computer2, Computer3, & Computer4).
Step 2: Now, connect the Computer1 & Computer2 to Switch1, and Computer3 & Computer4 to Switch2.
Step 3: For the Trunk port we need only one link so create a link between Switch1 and Switch2 and then click on ‘Fast Forward Time’ option.
Step 4: In the CLI of Switch1, run the command ‘int fa0/1’ then run ‘switchport access vlan 10’ command and then run ‘switchport mode access’ command.
Note: The command ‘switchport mode access’ is used to disable the DTP on the port and to access it manually.
Step 5: Run the command ‘int fa02’ then run ‘switchport mode access’ command and then run ‘switchport access vlan 20’ command.
Step 6: Again in the CLI of Switch2, run the command ‘int fa0/1’ then run ‘switchport access vlan 10’ command and then run ‘switchport mode access’ command.
Step 7: Run the command ‘int fa02’ then run ‘switchport mode access’ command and then run ‘switchport access vlan 20’ command.
Step 8: Now, to make a Trunk between the two switches, in the CLI of Switch1 run the command ‘int fastethernet 0/3’ and then run the ‘switchport mode trunk’ command and again use these commands in the CLI of Switch2 as well to make the port trunk.
Step 9: Click on the ‘Fast Forward Time’ option and in the CLI of Switch1 run the command ‘show int trunk’ where you can see the port3 is a trunk and the mode is on.
Now, through the single port, both VLAN10 users and VLAN20 users can easily communicate.
Why use VLAN Tagging?
Let’s say Computer1 will send the data to switch1 where the switch knows that the Computer1 is a member of VLAN10. Now, the switch will forward that data out of the trunk port along with adding a tag in that data to inform the other switch that this data belongs to VLAN10.
Here we use a single channel to send traffic for each & every VLAN. So, to identify that the incoming traffic belongs to which VLAN, the process called VLAN tagging is used.
What is DTP?
The DTP stands for Dynamic Trunking Protocol. Essentially, it prevents all the neighboring interfaces on the switch from becoming trunk ports, so it's known as DTP.
In DTP, we have two modes:
Dynamic Auto
Dynamic Desirable
Dynamic Auto: It allows the interface to become a trunk link in this mode. As long as the neighboring interface is configured as a trunk or desirable interface, the interface will become a trunk link. It is not possible to form a trunk if both switches have auto mode. It is also known as the default mode of CISCO.
Dynamic Desirable: This mode actively attempts to transform the link into a trunk link. Whenever the neighboring interface is set to trunk, desirable, or auto, the interface will become a trunk port.
So, in this video, we have understood what the trunk is, how to configure manual trunk links and what is the basic use of DTP.
Happy Learning :)
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