Configuring VLAN Chapter 14 powered by DJ 1

Chapter Objectives At the end of this Chapter you will be able to:  Understand basic concept of VLAN  Configure VLAN powered by DJ 2

VLAN Basics  Layer 2 switched networks are typically designed—as flat networks. With this configuration, every broadcast packet transmitted is seen by every device on the net- work regardless of whether the device needs to receive that data or not.  By default, routers allow broadcasts to occur only within the originating network, while switches forward broadcasts to all segments. it’s called a flat network is because it’s one broadcast domain Flat Network Structure powered by DJ 3

 You can solve many of the problems associated with layer 2 switching with VLAN i.e.  VLANs greatly enhance network security.  VLANs increase the number of broadcast domains VLAN 1 Host A VLAN 2 Host B powered by DJ 4

VLAN Memberships Static VLANs In Static Membership each switch port is configured manually with a VLAN Membership based upon which VLAN the host needed to be a member of. Dynamic VLANs On the other hand, a dynamic VLAN determines a node’s VLAN assignment automatically. Using intelligent management software, you can base VLAN assignments on hardware (MAC) addresses powered by DJ 5

Identifying VLANs There are two different types of links in a switched environment.  Access Ports An access port belongs to and carries the traffic of only one VLAN. Traffic is both received and sent in native formats with no VLAN tagging whatsoever  Trunk Ports A trunk link is a 100- or 1000Mbps point-to-point link between two switches, between a switch and router, or even between a switch and server, and it carries the traffic of multiple VLANs—from 1 to 4,094 at a time powered by DJ 6

Access and Trunk Links in a switched network powered by DJ 7

Frame Tagging  This frame identification method uniquely assigns a user-defined ID to each frame. Sometimes people refer to it as a “VLAN ID” or even “color.”  Once the frame reaches an exit that’s determined by the forward/filter table to be an access link matching the frame’s VLAN ID, the switch will remove the VLAN identifier. This is so the destination device can receive the frames without being required to understand their VLAN identification. powered by DJ 8

VLAN Identification Methods It’s how switches identify which frames belong to which VLANs, and there’s more than one trunking method.41.0  Inter-Switch Link (ISL) Inter-Switch Link (ISL) is a way of explicitly tagging VLAN information onto an Ethernet frame. This tagging information allows VLANs to be multiplexed over a trunk link through an external encapsulation method (ISL), which allows the switch to identify the VLAN membership of a frame over the trunked link. powered by DJ 9

 IEEE 802.1Q Created by the IEEE as a standard method of frame tagging, IEEE 802.1Q actually inserts a field into the frame to identify the VLAN. If you’re trunking between a Cisco switched link and a different brand of switch, you’ve got to use 802.1Q for the trunk to work. powered by DJ 10

VLAN Trunking Protocol (VTP)  Cisco created this one too. The basic goals of VLAN Trunking Protocol (VTP) are to manage all configured VLANs across a switched internetwork and to maintain consistency throughout that network VTP allows you to add, delete, and rename VLANs—information that is then propagated to all other switches in the VTP domain. powered by DJ 11

VTP Modes of Operation powered by DJ 12

 Server This is the default mode for all switches. The switch must be in server mode to be able to create, add, and delete VLANs in a VTP domain.  Client In client mode, switches receive information from VTP servers.  Transparent Switches In transparent mode don’t participate in the VTP domain or share its VLAN database, but they’ll still forward VTP advertisements through any configured trunk links. They can create, modify, and delete VLANs because they keep their own database. powered by DJ 13

Configuring VLANs  S1#config t  S1(config)#vlan ?  WORD ISL VLAN IDs  internal internal VLAN  S1(config)#vlan 2  S1(config-vlan)#name Sales  S1(config-vlan)#vlan 3  S1(config-vlan)#name Marketing  S1(config-vlan)#vlan 4  S1(config-vlan)#name Accounting powered by DJ 14

Routing between VLANs powered by DJ 15

Configuring Inter-VLAN Routing  By default, only hosts that are members of the same VLAN can communicate. To change this and allow inter-VLAN communication, you need a router or a layer 3 switch.  To support ISL or 802.1Q routing on a Fast Ethernet interface, the router’s interface is divided into logical interfaces—one for each VLAN. These are called sub interfaces. From a Fast Ethernet or Gigabit interface, you can set the interface to trunk with the encapsulation command: powered by DJ 16

 ISR#config t  ISR(config)#int f0/0.1  ISR(config-subif)#encapsulation ?  dot1Q IEEE 802.1Q Virtual LAN  ISR(config-subif)#encapsulation dot1Q ?  IEEE 802.1Q VLAN ID powered by DJ 17

Configuring VTP  All Cisco switches are configured to be VTP servers by default. To configure VTP, first you have to configure the domain name you want to use.  S1#config t  S1#(config)#vtp mode server  Device mode already VTP SERVER.  S1(config)#vtp domain Lammle  Changing VTP domain name from null to Lammle  S1(config)#vtp password hcl  Setting device VLAN database password to hcl powered by DJ 18

THANK YOU powered by DJ 19