Creating Virtual Local Area Networks (VLANs) in Cisco

A VLAN is a group of end stations with common requirements regardless of their physical location. VLANs have the same attributes as physical local area networks, but end stations can be grouped even if they are physical local area networks. Not physically on the same LAN segment. VLANs are typically mapped to IP subnetworks. For example, all terminals within a particular IP Subnets belong to the same VLAN. Traffic between VLANs must be routed. LAN port VLAN Membership is manually assigned per port VLAN (Virtual LAN) is a logical grouping of devices within the same broadcast domain. VLANs are typically configured on a switch by putting some interfaces in one broadcast domain and some interfaces in another broadcast domain. Each VLAN acts as a subset of switch ports on the Ethernet LAN.

Default Settings for VLANs:

• VLAN ID: 1; range: 1-4094
• VLAN name:
  • VLAN 1: “default”
  • Other VLANs: “VLANvlan_ID”
• 802.10 SAID: 10vlan_ID; range: 100001-104094
• MTU size: 1500; range: 1500–18190
• Translational bridge 1: 0; range: 0–1005
• Translational bridge 2: 0; range: 0–1005
• VLAN state: active: active, suspend
• Pruning eligibility:
  • VLANs 2-1001 are cropping eligible
  • VLANs 1006-4094 are not cropping eligible

VLANs Functionality:

1. VLAN helps in securing the network
2. .VLAN helps in QoS.
3. VLAN helps in fault management as users as isolated from each other.

Consider a topology:

Without any VLANs, a broadcast message by any of the PCs would reach all the PCs. All the PC would get the entire frame and process it, wasting CPU process time. When we isolate the PCs using VLAN, a broadcast message generated will stay within the VLAN.

Configure VLAN Interface Settings On Switch:

Step 1: Log in to the web-based application and select VLAN Management → Interface Settings.

Step 2: Choose an interface from the Interface Type drop-down list, click Go, and enter the list of ports or LAGs for the interface.

• Port: Select Port from the Interface Type drop-down list if you need to select only one port.
• Lag: Select the lag you want to configure from the interface type drop-down list. This affects the set of ports defined in the LAG configuration.

Step 3: Click the radio button for the port or LAG you want to change. Click the edit icon.

Step 4: From the drop-down menu, click the radio button corresponding to the desired VLAN mode for the interface.

Step 5: Click Apply, and then click Close.

Configure VLAN on links:

interface range f0/1-3
switchport access vlan 20
exi

Note: These practicals are executed on Cisco devices.