In preparation of our CCNA exam, we want to make sure we cover the various concepts that we could see on our Cisco CCNA exam. So to assist you, below we provided a CCNA VLan Cliff Notes article. This section will probably be most helpful to review immediately before you take your Cisco CCNA certification exam on test day!
If you have a 24 port Cisco switch and you plug a PC into each port of the Cisco switch, you have all 24 PCs on a single LAN via that Cisco switch. A VLAN is a Virtual LAN. Now if you still connect all 24 of those PCs to the same Cisco switch, but now you configure this managed Cisco switch to behave in a way in which it “virtually” breaks the switch into two separate switches…well, you have just created a VLAN. These two separate VLANs will each have their own subnet and will only broadcast to other PCs on the same VLAN. This way you get to use the Cisco switch to segment broadcast domain which until implementing this concept was only possible with a Cisco router which controlled or contained broadcasts to a particular subnet.
So a VLAN can be defined as a virtual broadcast domain. Instead of segmenting the broadcast domain with a router, you will segment it with a Cisco switch at layer 2. Each VLAN should have its own IP subnet.
Broadcast Control: Broadcasts generated in one VLAN are not propagated to other VLANs. So now to pass traffic between VLANs on the same Cisco switch, you must use a Cisco router.
Security: Control over each port and user which is not possible with hubs.
Flexibility & Scalability: Allow adding or removing users to broadcast domain regardless of their physical location
Two ways to assign VLANs:
Statically: The administrator assigns users to a VLAN. It works well on networks where users' movement is controlled. This is a commonly used method and most secure but has a lot of administrative overhead.
Dynamically: Determines a node's VLAN assignment automatically using software. Initial administration work required to build the database. Cisco's VLAN Management Policy Server (VMPS) is a MAC address-to-VLAN mapping database.
NOTE: Clients (PCs) on VLANs are unaware of their VLAN membership. Cisco routers, Cisco switches and servers can handle and recognize VLANs membership for each frame.
Access Link: Link that is part of one VLAN, called native VLAN. This is used to connect clients to their associated VLAN.
VLAN Trunking Protocols(VTP)
Inter-Switch Link(ISL): Cisco proprietary.
IEEE 802.1q: It inserts a field into the frame for VLAN identification; original frame is altered, not encapsulated.
LAN Emulation (LANE): Sends VLAN information over ATM links.
802.10: Sends VLAN information over FDDI links.
VLAN Trunk Protocols Operation
VTP Elements Mode of Operation:
Server Mode: This is the default mode of operation.
Client Mode: Receives and forwards VLAN updates. Updates its database but cannot make changes. If you want a switch to become a Server, make it a client first so that it receives all the updates then change it to Server.
I hope you found this article to be of use and it helps you prepare for your Cisco CCNA certification. Achieving your CCNA certification is much more than just memorizing Cisco exam material. It is having the real world knowledge to configure your Cisco equipment and be able to methodically troubleshoot Cisco issues. So I encourage you to continue in your studies for your CCNA exam certification.