Day 16 - VLANs (1)

Jeremy’s IT Lab lecture video:

Day 16 - VLANs (1)

---

Commands

Commands List

VLAN Show Commands

4. VLANs

• show vlan
• show vlan brief --> Shows a brief list of VLANs and the access ports that are using them

Link to original

VLAN Interface Commands

Switchport

1. General

• switchport mode type { access / trunk / dynamic auto / dynamic desirable } --> Configures the switchport type for VLANs
• switchport nonegotiate --> Disables Dynamic Trunking Protocol (DTP) requests between switches (setting the switch to access mode does the same thing)

2. Access Ports

• switchport access vlan vlan-id --> Changes the access port’s VLAN to the specified VLAN ID
• switchport voice vlan vlan-id --> Assigns VOIP (Voice over IP) traffic to be tagged with a specific VLAN ID (Done while the switchport is in access mode)

3. Trunk Ports

• switchport trunk encapsulation mode {auto / negotiate / dot1q / isl}
• switchport trunk allowed vlan argument {vlan-id/ add vlan-id / remove vlan-id / all / none / except vlan-id}
  (Multiple VLANs can be used in add, remove and except by putting a comma in between the vlan-IDs)
• switchport trunk native vlan vlan-id

Link to original

---

VLANs

• A LAN is a single broadcast domain, including all devices in it. And a broadcast domain is a group of devices which will receive a broadcast frame (Dest. MAC ffff.ffff.ffff) sent by any of the members.
• VLANs logically separate a switch’s LANs on Layer 2.
• (PS. Subnets logically separate LAN networks on Layer 3)

Switchport Types

There are two switchport types which use VLANs:

1. Access ports (untagged ports):
   • An access port is a switchport which belongs to a single VLAN, and usually connects to end hosts like PCs. Traffic is ==NOT== tagged when sent over this interface.
2. Trunk ports (tagged ports):
   • A trunk port carries traffic from multiple VLANs. Traffic is tagged on this interface except if the data is being sent on the native VLAN.