1. Large-scale (Campus) Lan design (Part II)
VLANs
Hierarchical LAN design

2. Virtual LANs (VLANs)
VLANs consist of end systems that are members of a single logical broadcast domain.
A VLAN has no physical proximity constraints for the broadcast domain
A VLAN can span various pieces of network equipment that support VLAN trunking protocols between them
Without a router, hosts in 1 VLAN can’t communicate with hosts in another VLAN

3. Single-switch VLANs

4. VLAN Benefits VLANs break networks into smaller broadcast domains
VLANs provide security
Easier network management
Well-behaved VLANs usually follow 80/20 network design rule

5. VLAN Example

6. VLAN Trunking
Trunk – high-speed connection between internetworking devices
Switches use Trunking protocol to exchange information about VLAN configuration (e.g. IEEE 802.1Q, Cisco’s ISL)
With trunking, tags are added to all the frames traveling on the trunk

7. VLANs are shared through trunks

8. VLAN Implementation By port – each port must belong to only 1 VLAN
By protocol – single port can support more than 1 VLAN
By a user-defined value – e.g. MAC address

9. Single switch VLANs

10. Backbone
Traditional
Collapsed

11. Redundancy in the Backbone

12. Distributed backbone (multiple collapse points)

13. Hierarchical Design
Access
Distribution
Core

14. Hierarchical Design

15. Central Routing

16. Distributed Routing

17. Small campus

18. Medium campus

19. Large campus