Chabot College ET Cisco Semester 3 Chapter 3 VLANs M. McGregor, Los Medanos College, Pittsburg, CA

Chabot College Introduction to VLANs

Chabot College What is a VLAN?

Chabot College Why create VLANs?

Chabot College Switches are the core of VLANs

Chabot College VLAN Switching and Filtering Each switch has the intelligence to make filtering and forwarding decisions by frame, based on VLAN metrics defined by network managers, and to communicate this information to other switches and routers within the network.

Chabot College Frame filtering and tagging The most common approaches for logically grouping users into distinct VLANs are: frame filtering frame tagging

Chabot College Frame Filtering

Chabot College Tradeoffs with frame filtering Filter-based VLANs do not scale well because each frame has to be referenced to a lookup table. The IEEE 802 committee has adopted frame tagging as the standard because it is more scalable.

Chabot College IEEE 802 VLAN Standardization

Chabot College Frame Tagging

Chabot College VLAN Flexibility

Chabot College Problems with broadcasts

Chabot College Problems with broadcasts When no routers are placed between switches, broadcasts (Layer 2 transmissions) are sent to every switched port. This is commonly referred to as a “flat” network where there is one broadcast domain across the entire network

Chabot College VLANs can control broadcasts

Chabot College VLANs can provide security

Chabot College VLANs provide flexibility

Chabot College Where are the routers? Layer 3 communication, either embedded in the switch or provided externally, is an integral part of any high-performance switching architecture.

Chabot College What are hubs good for?

Chabot College Leveraging your investment

Chabot College Port-Centric VLANs

Chabot College Port-centric VLANs VLAN Membership by port maximizes forwarding performance because:  Users are assigned by port.  VLANs are easily administered  Maximizes security between VLANs  Packets do not “leak” into other domains  VLANs and membership are easily controlled across network

Chabot College Static VLANs

Chabot College Dynamic VLANs Dynamic VLANs are ports on a switch that can automatically determine their VLAN assignments.

Chabot College VLANs across backbones

Chabot College VLANs across backbones Fast Ethernet - ISL (Inter-Switch Link) FDDI - IEEE ATM - LAN Emulation (LANE)

Chabot College VTP - VLAN Trunk Protocol VTP Domain VTP Configuration revision number VLAN IDs (ISL) Emulated LAN names (ATM) SAID values (FDDI) MTU Frame format VLAN configuration