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| 2.3 |  | VLAN Types |
| 2.3.2 |  | End-to-end VLANs |

VLANs can exist either as end-to-end networks (campus-wide) or they can exist inside of a limited geographic (local) boundaries. An end-to-end VLAN network comprises the following characteristics:

- Users are grouped into VLANs independent of physical location and dependent on group or job function.
- All users in a VLAN should have the same 80/20 traffic flow patterns.
- As a user moves around the campus, VLAN membership for that user should not change.
- Each VLAN has a common set of security requirements for all members.

Backbone links in a switched LAN should be faster than access level links. Starting in the wiring closet, 10-megabit-per-second (Mbps) dedicated Ethernet ports are provisioned for each user. Each color represents a subnet and, because people have moved around over time, each switch eventually becomes a member of all VLANs. Fast Ethernet Inter-Switch Link (ISL) or IEEE 802.1Q is used to carry multiple VLAN information between the wiring closets and the distribution-layer switches.

ISL is a Cisco-proprietary protocol that maintains VLAN information as traffic flows between switches and routers. IEEE 802.1Q is an open-standard VLAN tagging mechanism that predominates in modern switching installations.

Workgroup servers operate in a client/server model, and attempts have been made to keep users in the same VLAN as their server to maximize the performance of Layer 2 switching and keep traffic localized.

In the core, a router allows inter-subnet communication. The network is engineered, based on traffic flow patterns, to have 80 percent of the traffic within a VLAN and 20 percent crossing the router to the enterprise servers and to the Internet and WAN. End-to-end VLANs allow devices to be grouped based upon resource usage. This includes such parameters as server usage, project teams, and departments. The goal of end-to-end VLANs is to maintain 80 percent of the traffic on the local VLAN.

As corporate networks move to centralize their resources, end-to-end VLANs have become more difficult to maintain. Users are required to use many different resources, many of which are no longer in “their” VLAN. Because of this shift in placement and usage of resources, VLANs now are frequently created around geographic (local) boundaries rather than commonality boundaries.