Implement VLAN based solution, given a network design and a set of requirements (CCNP SWITCH 642-813)
Describe how VLANs create logically separate networks and the need for routing between them (CCNA 200-120)
Configure and verify VLANs (CCNA 200-120)
What is a VLAN?
A VLAN is a layer 2 logical network. Devices on that VLAN are part of the same broadcast domain, meaning any broadcasts sent on that VLAN are sent and received to devices solely on that VLAN. Broadcasts do not transmit to other VLANs.
Configuring a VLAN on a Cisco switch is very simple. Enter global configuration mode:
SwitchA(config)# vlan 10 SwitchA(config-vlan)# name SERVERS
We issue the vlan command followed by the VLAN number. In the next line I label VLAN 10 as SERVERS.
To associate a device on VLAN 10 we must enter interface configuration mode for the port that should be in VLAN 10. If a server was on fast ethernet port 15 then I would issue the following commands:
SwitchA(config)#interface f0/15 SwitchA(config-if)#switchport mode access SwitchA(config-if)#switchport access vlan 10
switchport mode access makes this port an access port. A trunk cannot be formed over an access port.
switchport access vlan 10 is the actual command that associates the interface with that VLAN.
There are a couple of ways to verify our configuration:
show vlan brief
This command would display the VLANs configured on the switch. We should see VLAN 10 and int Fa0/15 associated with that VLAN:
10 SERVERS active Fa0/15
View the interface configuration. We can check the running-config to verify we have associated the interface to the right VLAN:
SwitchA#sh run interface f0/15 Building configuration... Current configuration : 85 bytes ! interface FastEthernet0/15 switchport access vlan 10 switchport mode access end
Take time to consider your VLAN design. Determine whether you want to implement an End-to-End strategy or just use local VLANs. Learn more about these strategies over at this post.