CCNA: VLANs/ VTP

2 minute read

Description:

Do not use DTP (auto), set all ports to access or trunk mode!

To create a VLAN on a switch:

1
2
3

   Switch(config)#vlan 100
   Switch(config-vlan)#name ITDept
   Switch(config-vlan)#exit

To create a VLAN on a router:

1
2
3
4
5
6
7
8
9
10

   Router#vlan database
   Router(vlan)#vlan 10
   Router(vlan)#exit
   Router#config t
   Router(config)#int vlan 10
   Router(config-if)#ip address 192.168.1.1 255.255.255.0
   Router(config-if)#description IT_VLAN
   Router(config-if)#ipv6 address
   Router(config-if)#no shut
   Router(config-if)#end

To assign a VLAN to an interface:

1
2
3
4
5
6
7
8

   Switch(config)#vlan 99
   Switch(config-vlan)#name Management
   Switch(config)#config t
   Switch(config)#interface f0/1
   Switch(config-if)#switchport access vlan 99 # this tells the port to use vlan 99 only
   Switch(config-if)#interface vlan 99 # just going into the interface brings it up
   Switch(config-if)#ip address 192.168.99.1 255.255.255.0
   Switch(config-if)#end

To assign multiple VLANs to an interface (trunking):

1
2
3
4
5
6
7
8
9

   Switch(config)#int fa0/0
   Switch(config-if)#switchport mode trunk # this could be all you need to establish trunks between two switches. You don't have to establish the VLANs.
   Switch(config-if)#switchport nonegotiate # recommended to disable DTP
   Switch(config-if)#switchport trunk native vlan 99 # You have to change the native vlan from within an interface. By default this is VLAN1 and should be changed for security.
   Switch(config-if)#switchport trunk allowed vlan 100 # this only allows VLAN 100
   Switch(config-if)#switchport trunk allowed vlan 10, 20-30 # over-rides it to include vlans 10 and 20-30
   Switch(config-if)#switchport trunk allowed vlan add 12 # this is the correct way to add a new VLAN without overridding
   Switch(config-if)#switchport trunk encapsulation dot1q # uses the open standard 802.1q for encapsulation (most common)
   Switch(config-if)#end

Show Commands:

1
2
3
4
5

   show vlan
   show vlan brief
   show interfaces vlan
   show interfaces f0/1 switchport
   show interfaces f0/2 trunk

VTP:

VTP is a Cisco protocol that allows you to create a client/server way to share VLAN info for all switches in a domain.

Enable VTP Server:

1
2
3
4
5
6

   Switch(config)#vtp domain Mydomain.net #enables VTP - domain must match on all switches
   Switch(config)#vtp password cisco # password must match on all switches
   Switch(config)#vtp mode server # set this to server, client, or transparent
   Switch(config)#vtp version 2 #note that catalyst switches can only run v1 and v2/1 are NOT compatible!!
   Switch(config)#vtp pruning # This will tell the switch that VLANs not having any access ports on the end switch are removed from the trunk.
   Switch(config)#end

Enable VTP Clients:

1
2
3
4
5

   Switch(config)#vtp domain Mydomain.net #enables VTP - domain must match on all switches
   Switch(config)#vtp password cisco # password must match on all switches
   Switch(config)#vtp mode client # set this to server, client, or transparent
   Switch(config)#vtp version 2 #note that catalyst switches can only run v1 and v2/1 are NOT compatible!!
   Switch(config)#end

To set VTP Pruning:

1
2
3
4

   # Pruning is disabled by default. You enable it globally and then use it per interface.
   Switch(config)#vtp pruning
   Switch(config)#int fa0/2
   Switch(config-if)#switchport trunk pruning vlan remove 3,10-15 # more info http://www.lab.dit.upm.es/~labrst/config/ciscopedia/switchport%20trunk%20pruning.htm

Show Commands:

1
2
3
4
5

   show vtp status
   show vtp password
   show vtp counters # VTP servers should show only the received counters incrementing, while any VTP clients should show only the transmitted counters incrementing.
   show interface switchport
   show interface trunk

Suggested Training Opportunities

  1. Free Resources
  2. Instructor led:

Comments

You May Also Enjoy