VLAN TRUNKS

EXPLICIT MANUAL TRUNKING

PROCEDURE

  1. Configure SW1 interface gi0/0 as a manual trunk port using vlan 99 as the native VLAN and using 802.1Q trunking protocol instead of ISL protocol

  2. Configure SW2 interface gi0/0 as a manual trunk port using vlan 99 as the native VLAN and using 802.1Q trunking protocol instead of ISL protocol

  3. Verify trunking between the two switches

  4. Get a detailed view of the trunking configuration on a specific interface

IMPLEMENTATION

01.Switch1(config)# vlan 99
   Switch1(config-vlan) name NATIVE_VLAN
   Switch1(config)# interface gi0/0
   Switch1(config)# switchport trunk encapsulation dot1q
   Switch1(config-if)# switchport mode trunk
   Switch1(config-if)# switchport trunk native vlan 99
02.Switch2(config)# vlan 99
   Switch2(config-vlan) name NATIVE_VLAN
   Switch2(config)#  interface gi0/0
   Switch2(config)# switchport trunk encapsulation dot1q
   Switch2(config-if)# switchport mode trunk
   Switch2(config-if)# switchport trunk native vlan 99
03.Switch1# show interfaces trunk
   Switch2# show interfaces trunk
04.Switch1# show interface g0/0 switchport
   Switch2# show interface g0/0 switchport
    * VLAN 99 must be created else it will state
      "Trunking Native Mode VLAN: 99 (Inactive)"

    * both interfaces have to match or the trunk link will not form
      properly. Once the trunk link is formed, all VLAN traffic can
      pass over the trunk link

DYNAMIC/ACTIVE TRUNKING

Dynamic/Active is where a DTP mode actively initiates & responds to DTP messages

PROCEDURE

  1. Configure SW1 interface gi0/0 to actively initiate trunking using vlan 99 as the native VLAN and using 802.1Q trunking protocol instead of ISL protocol

  2. Configure SW2 interface gi0/0 to actively initiate trunking using vlan 99 as the native VLAN and using 802.1Q trunking protocol instead of ISL protocol

  3. Verify trunking between the two switches

  4. Get a detailed view of the trunking configuration on a specific interface

  5. Troubleshoot and verify DTP

IMPLEMENTATION

01.Switch1(config)# vlan 99
   Switch1(config-vlan) name NATIVE_VLAN
   Switch1(config)# interface gi0/0
   Switch1(config-if)# switchport mode dynamic desirable
   Switch1(config-if)# switchport trunk native vlan 99
02.Switch2(config)# vlan 99
   Switch2(config-vlan) name NATIVE_VLAN
   Switch2(config)# interface gi0/0
   Switch2(config-if)# switchport mode dynamic desirable
   Switch2(config-if)# switchport trunk native vlan 99
    * You must create VLAN 99; else it the port configuration will
      say VLAN 99 (inactive)
03.Switch1# show interfaces trunk
   Switch2# show interfaces trunk
04.Switch1# show interface g0/0 switchport
   Switch2# show interface g0/0 switchport
    * VLAN 99 must be created else it will state
      "Trunking Native Mode VLAN: 99 (Inactive)"
    * both interfaces have to match or the trunk link will not
      form properly. Once the trunk link is formed, all VLAN traffic
      can pass over the trunk link
05.Switch1# show interfaces trunk
   Switch2# show interface gi0/0 switchport
    * with these commands, you are looking for the following:
       - administrative mode:
       - operational mode:
       - status: trunking
       - native vlan:

DYNAMIC/PASSIVE TRUNKING

Dynamic/Passive is where a DTP mode passively waits for other side to send DTP messages

PROCEDURE

  1. Configure SW1 interface gi0/0 to passively trunk and wait for the other side to send DTP messages using vlan 99 as the native VLAN and using 802.1Q trunking protocol instead of ISL protocol

  2. Configure SW2 interface gi0/0 to passively trunk and wait for the other side to send DTP messages using vlan 99 as the native VLAN and using 802.1Q trunking protocol instead of ISL protocol

  3. Verify trunking between the two switches

  4. Get a detailed view of the trunking configuration on a specific interface

  5. Troubleshoot and determine why the interfaces are not trunking

  6. Fix the issue IOT have the two switches form a "trunk" link

IMPLEMENTATION

01.Switch1(config)# vlan 99
   Switch1(config-vlan) name NATIVE_VLAN
   Switch1(config)# interface gi0/0
   Switch1(config-if)# switchport trunk encapsulation dot1q
   Switch1(config-if)# switchport mode dynamic auto
   Switch1(config-if)# switchport trunk native vlan 99
02.Switch2(config)# vlan 99
   Switch2(config-vlan)  name NATIVE_VLAN
   Switch2(config)# interface gi0/0
   Switch2(config-if)# switchport trunk encapsulation dot1q
   Switch2(config-if)# switchport mode dynamic auto
   Switch2(config-if)# switchport trunk native vlan 99
03.Switch1# show interfaces trunk
   Switch2# show interfaces trunk
    * No trunk links will be established because both links are in a
      passive state & are waiting for either side to initiate DTP
      messages which will not happen when a trunk port is set to
      dynamic auto
04.Switch1# show interface g0/0 switchport
   Switch2# show interface g0/0 switchport
    * VLAN 99 must be created else it will state
      "Trunking Native Mode VLAN: 99 (Inactive)"
05.Switch1# show interfaces trunk
   Switch2# show interface gi0/0 switchport
    * with these commands, you are looking for the following:
       - administrative mode:
       - operational mode:
       - status: trunking
       - native vlan:
07.Switch1(config)# interface gi0/0
   Switch1(config-if)# switchport mode dynamic desirable
   Switch1(config-if)# do show interfaces trunk
   Switch1(config-if)# do show interface gi0/0 switchport

    * Having the two switches on dynamic auto will not form a trunk
       - This is because both link will wait for the other side
         to send DTP message which will never happen
       - To fix the issue, configure one side to be either an
         explicit trunk port or dynamic desirable state
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