What is VLAN? How to configure VLAN on CISCO 3500XL switch ?

Published by naveed at 7:22 PM under Cisco

Planing to Configure in your Orgnization ? this is really good to use VLAN, becasue traditional network designs use routers to create broadcast domains and limit broadcasts between multiple subnets. This prevents broadcast floods in larger networks from consuming resources, or causing unintentional denials of service unnecessarily. Unfortunately, the traditional network design methodology has some flaws in design Geographic Focus - Traditional network designs focus on physical locations of equipment and personnel for addressing and LAN segment placement.

Because of this there are a few significant drawbacks: Network segments for physically disjointed organizations cannot be part of the same address space. Each physical location must be addressed independently, and be part of its own broadcast domain. This can force personnel to be located in a central location, or to have additional latency or connectivity shortfalls. Relocations of personnel and departments can become difficult, especially if the original location retains its network segments. Relocated equipment will have to be reconfigured based on the new network configuration.

A VLAN solution can alleviate both of these drawbacks by permitting the same broadcast domain to extend beyond a single segment.

Additional Bandwidth Usage - Traditional network designs require additional bandwidth because packets have to pass through multiple levels of network connectivity because the network is segmented. A proper VLAN design can ensure that only devices that have that VLAN defined on it will receive and forward packets intended as source or destination of the network flow.

How to Configure a VLAN...

Connect to your Cisco Switch

enter enable mode

BWL-SW#sh vlan brief

VLAN Name                             Status    Ports
---- -------------------------------- --------- -------------------------------
1    default                          active    Fa0/1, Fa0/2, Fa0/3, Fa0/4,
                                                Fa0/5, Fa0/6, Fa0/7, Fa0/8,
                                                Fa0/9, Fa0/10, Fa0/11, Fa0/12,
                                                Fa0/13, Fa0/14, Fa0/15, Fa0/16,
                                                Fa0/17, Fa0/18, Fa0/19, Fa0/20,
                                                Fa0/21, Fa0/22, Fa0/23, Fa0/24,
                                                Fa0/25, Fa0/26, Fa0/27, Fa0/28,
                                                Fa0/29, Fa0/30, Fa0/31, Fa0/32,
                                                Fa0/33, Fa0/34, Fa0/35, Fa0/36,
                                                Fa0/40, Fa0/41, Fa0/42, Fa0/43,
                                                Fa0/44, Fa0/45, Fa0/46, Fa0/47,
                                                Fa0/48, Gi0/1, Gi0/2
1002 fddi-default                     active
1003 token-ring-default               active
1004 fddinet-default                  active
1005 trnet-default                    active

Now to create a VLAN:

BWL-SW#vlan database

BWL-SW(vlan)#vlan 150 name sales

VLAN 150 added:

Name: sales

BWL-SW(vlan)#apply

BWL-SW(vlan)#exit

BWL-SW#conf t

Enter configuration commands, one per line. End with CNTL/Z.

BWL-SW(config)#interface fastEthernet 0/40

BWL-SW(config-if)#switchport access vlan 100

BWL-SW(config-if)#^Z

BWL-SW#sh vlan brief
VLAN Name                             Status    Ports
---- -------------------------------- --------- -------------------------------
1    default                          active    Fa0/1, Fa0/2, Fa0/3, Fa0/4,
                                                Fa0/5, Fa0/6, Fa0/7, Fa0/8,
                                                Fa0/9, Fa0/10, Fa0/11, Fa0/12,
                                                Fa0/13, Fa0/14, Fa0/15, Fa0/16,
                                                Fa0/17, Fa0/18, Fa0/19, Fa0/20,
                                                Fa0/21, Fa0/22, Fa0/23, Fa0/24,
                                                Fa0/25, Fa0/26, Fa0/27, Fa0/28,
                                                Fa0/29, Fa0/30, Fa0/31, Fa0/32,
                                                Fa0/33, Fa0/34, Fa0/35, Fa0/36,
                                                Fa0/40, Fa0/41, Fa0/42, Fa0/43,
                                                Fa0/44, Fa0/45, Fa0/46, Fa0/47,
                                                Fa0/48, Gi0/1, Gi0/2
150 sales                            active Fa0/37, Fa0/38, Fa0/39, Fa0/40
1002 fddi-default                     active
1003 token-ring-default               active
1004 fddinet-default                  active
1005 trnet-default                    active
BWL-SW#copy running-config startup-config
Destination filename [startup-config]?
Building configuration...
[OK]
BWL-SW#