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

Single switch VLANs

9

Multi-switch VLANs

10

11

Backbone Traditional

Collapsed

12

Redundancy in the Backbone

13

Distributed backbone (multiple collapse points)

14

Distributed backbone (multiple collapse points)

15

Hierarchical Design Access Distribution Core

16

Hierarchical Design

17

Central Routing

18

Distributed Routing

19

Small campus

20

Medium campus

21

Large campus