Lab 13: Setting Switchports to Dynamic

Lab Objective:

The objective of this lab exercise is for you to learn and understand how to set the auto-negotiation type on a trunk link.

Lab Purpose:

Switch interfaces are set to automatically attempt to create a trunk link when connected to another switch. You need to know how to set either dynamic desirable or dynamic auto.

Certification Level:

This lab is suitable for CCENT exam preparation.

Lab Difficulty:

This lab has a difficulty rating of 5/10.

Readiness Assessment:

When you are ready for your certification exam, you should complete this lab in no more than 10 minutes.

Lab Topology:

Please use the following topology to complete this lab exercise:

Task 1:

In preparation for the configuration, configure a hostname on Sw1 as well as Sw2.

Task 2:

Configure Sw1 so that auto-negotiation of trunking is set to dynamic auto.

Task 3:

Configure Sw2 so that auto-negotiation of trunking is set to dynamic desirable.

Task 4:

Verify your configurations with the appropriate show commands (illustrated in Task 3 below).

Configuration and Verification

Task 1:

For reference information on configuring hostnames, please refer to earlier labs.

Task 2:

Sw1#show int fast0/1 switchport 
Name: Fa0/1 
Switchport: Enabled 
Administrative Mode: dynamic auto 
Operational Mode: static access 
Administrative Trunking Encapsulation: dot1q 
Operational Trunking Encapsulation: native 
Negotiation of Trunking: On 
Access Mode VLAN: 1 (default) 
Trunking Native Mode VLAN: 1 (default)

The interface is actually already set to dynamic auto, which is the default setting for this model of switch (yours may vary). Let’s put the command in anyway.

Sw1(config)#int fast0/1 
Sw1(config-if)#switchport mode dynamic auto

Task 3:

NOTE: You need to have at least one switch set to either trunk or dynamic desirable for a trunk link to form.

Sw2#show int fast0/1 sw 
Name: Fa0/1 
Switchport: Enabled 
Administrative Mode: dynamic auto 
Operational Mode: static access 
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: native 
Negotiation of Trunking: On 
Access Mode VLAN: 1 (default) 

Sw2#show interface trunk 

Sw2(config)#int fast0/1 
Sw2(config-if)#switchport mode dynamic desirable 
Sw2(config-if)#end 

Sw2#show int fast0/1 switchport 
Name: Fa0/1 
Switchport: Enabled 
Administrative Mode: dynamic desirable 
Operational Mode: trunk 
Administrative Trunking Encapsulation: dot1q 
Operational Trunking Encapsulation: dot1q 
Negotiation of Trunking: On 
Access Mode VLAN: 1 (default) 
Trunking Native Mode VLAN: 1 (default) 

Sw2#show interface trunk 
Port        Mode         Encapsulation  Status        Native vlan 
Fa0/1       desirable    n-802.1q       trunking      1

The n indicates that it negotiated the encapsulation type.


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