2 - VLANS and Trunking

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TYPE OF VLANS
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STANDARD VLANS
* Range  1 - 1005
* VLAN 1 :
- If a trunk port receives a frame without a tag by default asumes is for vlan 1
- Do not delete it, it is use for exchange in the control plane for a lot of protocols
- VTP will not prune it you have to do it manually from trunks
- It is just for the control plane so don't assign it to any port
- It is a bad design practice use vlan 1 in a trunk
- All ports are assigned for default to vlan 1
* VLAN 1002 - 1005
- its is used in FDDI, Token Ring vlans
- Do not delete it, it is use for exchange in the control plane for a lot of protocols
- VTP will not prune it you have to do it manually from trunks
- It is just for the control plane so don't assign it to any port
- It is a bad design practice use vlan 1002 -1005 in a trunk

EXTENDED VLANS
* Range 1006 - 4094
* Used in VTP transparent mode or VTP version 3
  - VTP version 3 advertises extended vlans when you create them
  - VTP version 3 advertises private vlans
  - Vlans created in transparent mode are locally significant so they must be created in every switch
* There is an internal range which can't not be used but that depends on the platform
INTERNAL VLANS
* Reserverd for internal applications
* This internal range changes on each platform
* To see the numbers used in internal vlans use the command
  - show vlan internal use

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CREATING VLANS
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* A spanning-tree protocol and mac address table instance is created per each vlan you create
* To check the vlans created use the command "show vlan brief", "show spanning-tree vlan"
* A switch in client mode doesn't allow to create vlans..command "vtp mode client"

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ETHERNET PORT TYPES
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LAYER 2 SWTICHPORTS
* Access 
  - One vlan assigned to it
* Trunk
  - Carry multiple vlans
* Tunnel
  - A vlan into vlan encapsulation - transparent layer 2 VPN
* Dynamic
  - DTP negociate if the port is going to be a trunk or access port

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LAYER 2 TRUNKING
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* 802.1Q
  - Open standard
  - Untagged frames are sent to native vlan
* DTP (Dynamic trunking protocol)
  - The switches negociate in a dynamic way which port wil be in trunk mode
* Commands to check trunk ports
  - Show interface trunk
  - Show interfaces switchport (detail information like: which vlan the port belongs, switchport (access, trunk), native vlan etc
  - Show spanning-tree (vlan|interface)

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DTP Negociation
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* Enabled by default
* DTP desirable mode
  - Begins trunking negociation
  - commands:
    - switchport mode dynamic desirable (negociate encapsulation: 802.1Q or isl)
    - switchport mode trunk (encapsulation must be 802.1Q)
* DTP auto mode
  - Waits for trunking negociation
  - Commands : switchport mode dynamic auto

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Disable DTP Negociation
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* Commands:
  - switchport nonegociate
  - switchport mode access
  - switchport mode dot1q-tunnel
* Command to check DTP negociation
  - show interface switchport

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Manual Trunk Prunning
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* Why prunning?: When there is no vlans in common between the two switches to avoid innecesary broadcast or traffic
* All vlans (1 -4094) allowed to forward over the link
* Command for manual pruning
  - switchport trunk allowed vlan
* Command to check manual pruning
  - show interface trunk
  - show interface switchport

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Commands
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* show vlan brief (to check if vlans were created)
* show interface status (quick look of the links status)
* show interface switchport (detail link status)
* show interface trunk (encappsulation, dtp mode, vlans active and forwading)
* show spanning-tree (vlan | interface) (To check if traffic is going to flow out the interface)