Helpful Hints about INE’s virtual lab environment:

• Save your configuration changes frequently in the event that you get locked out of a device or lose connectivity
• If you are suddenly logged out of the GNS3 lab environment and log back in again, you may see the prompt, “Another GNS3 instance is running, continue? (Y/N)”. Select “Yes”

• If you ever lose console access to one (or more) of your devices you will need to reboot the Ubuntu Virtual Machine that is hosting your GNS3 lab environment. To do this,

  • Minimize your GNS3 window
  • Open the “Terminal” app within the Ubuntu device

  

  • Type “reboot” within the Terminal window
  • Wait 20-30 seconds and then click the “Reconnect” option to log back in.

Solutions:

This lab started up with a pre-configuration which included some VLANs and trunking. By default, a trunk port forwards all known VLANs. For security or other purposes that behavior can be modified by suppressing unnecessary VLANs on a trunk port. According to the task, we must configure Sw1 to allow VLAN 200 on its Gig3/0 interface, and Sw1 and Sw2 must be configured to allow both VLANs 100 and 200 on their Gig1/0 interface. We must also configure Sw3 to allow VLAN 200 on its Gig3/0 interface.

    Sw1:
    interface Gig1/0
     switchport trunk allowed vlan 100,200
    !
    interface Gig3/0
     switchport trunk allowed vlan 200

    Sw2:
    interface Gig1/0
     switchport trunk allowed vlan 100,200

    Sw3:
    interface Gig3/0
     switchport trunk allowed vlan 200

Verification

We can filter the VLANs on an interface using the switchport trunk allowed-vlan add | remove | none | except commands. In this particular task, we have configured the trunk interfaces to allow only necessary VLANs. It can be verified by using the show interface trunk command as shown below.

    Sw1#show interfaces trunk

    Port        Mode             Encapsulation  Status            Native vlan
    Gi1/0       on               802.1q         trunking      1
    Gi3/0       on               802.1q         trunking      1

    Port        Vlans allowed on trunk
    Gi1/0       200,300
    Gi3/0       200

    ###################

    Sw2#show interfaces trunk

    Port        Mode             Encapsulation  Status            Native vlan
    Gi1/0       on               802.1q         trunking      1

    Port        Vlans allowed on trunk
    Gi1/0       100,200

    ####################

    Sw3#show interfaces trunk

    Port        Mode             Encapsulation  Status            Native vlan
    Gi3/0       on               802.1q         trunking      1

    Port        Vlans allowed on trunk
    Gi3/0       200