Trunking

Connecting VLANs

• VLANs can exist on multiple switches
• Connecting VLANs without trunks
  • Requires access links (one per VLAN)
  • Doesn't scale well
• Better alternative is trunk links
  • Cisco sends all traffic across the trunk link

• Uplinks are actually just associated with the VLAN
• IS almost like the network is splitted right down the middle

Trunking

• Instead of using individual wires for each VLAN

• Trunk link carries frames from all the different VLANs

• IEEE 802.1q

• Trunk port tags on egress

• Tag removed on ingress

• Connecting VLANs with trunks

  • The opposite of an access point.
  • Requires a single link
    • Physical
    • Logical

• Trunks carry all VLANs by default

  • Can set allowed lists on trunks

• Native VLAN is untagged

• VLAN tags gives us the ability to isolate our traffic

  • Also gives us the ability to do quality of service