A VLAN is a group of end stations with a common set of requirements, independent of physical location. VLANs have the same attributes as a physical LAN but allow you to group end stations even if they are not located physically on the same LAN segment.
VLANs are usually associated with IP subnetworks. For example, all the end stations in a particular IP subnet belong to the same VLAN. Traffic between VLANs must be routed. LAN port VLAN membership is assigned manually on an port-by-port basis.
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So let us assume there are no VLANs, what happens here is: Since the basic functinality of a switch is to flood if the destination MAC address is not present in its CAM table (And also if it's cam table is full).. we will see a lot of broadcast messages all of the above said usages.
And also let us take the example of the VoIP ... since there are no VLANs and switch is expereincing a lot of broadcast messages and the users are using VoIP obviously some of the packets will drop because of the broadcast storm that switch is experiencing. So there will be a lot of disturbance in that call.. And same thing applies all the above types of traffic.
So inorder to overcome the above issues we need seperate the traffic types which means broadcast domains by creating virtual LANs.. in this way VLANs seperate layer 2 traffic to enhance stability and security.
Agian how securty is achieved : simple inorder to communicate between two VLANs you need a layer3 device (a router) where we cann assign ACLs like which VLANs traffic to pass or bypass it.
And also VLANs are location independent it means it can span to multiple switches.. untill the user belong to the same VLAN he can communicate with the members in same VLAN without using layer3 device....
This is actually a pretty cool feature, i didn't even know it existed until I was looking for a solution to advertise a subnet (prefix in BGP talk), only if a certain condition existed. This is exactly what conditional advertisements does
j ai une question j ai achete un routeur cisco 887VA-k9 , je le configuré avec la configuration ci- dessous
si je le lier avec mon pc portable sur l un de ses ports directement ça marche toute est bien ( la connexion internet + m...
Attached policy provides CLI access to the Cisco 4G router over text messaging. Two files are in the attached .tar file:
2. PDF with instructions on how to load and use the .tcl file.