VLAN Memberships

VLAN members can communicate with other members only on the same VLAN; for example, a member from VLAN 100 cannot communicate with a member from VLAN 200. Inter-VLAN communication is possible only with the addition of routing functionality, either with a route-switching module (RSM) in the VLAN switch, or a router external to the VLAN switch.

NOTE

The RSM provides Layer-3 switching at more than one million packets per second (pps) between switched VLANs.

VLAN members are assigned one of three ways, depending upon the VLAN implementation. These are:

• Port based VLAN The systems manager (or administrator) assigns each port of a switch to a VLAN. For example, ports 6 through 10 might be assigned to the R&D VLAN, ports 1 through 4 to the Marketing VLAN, and ports 4 through 6 to the Sales VLAN. The main drawback of VLANs defined by port is that the systems manager must reconfigure VLAN membership when a user moves from one port to another.

• MAC address-based VLANs Membership is defined by the source or destination MAC (hardware address). The advantage of this model is that you do not need to reconfigure the VLAN switch when a user makes a move to a different port. The issue with MAC address-based VLANs is that a single MAC address cannot be a member of multiple VLANs without extensive effort and configuration.

• Layer-3 VLANs Based on Layer-3 (OSI Model Network Layer) information, take into account the protocol type (IP, NetBIOS) and the Layer-3 addresses when you are determining VLAN membership. One of the benefits of this method is that users can move their workstation without having to reconfigure their network addresses. The issue with Layer-3 VLANs is that Layer-3 gives you slow performance.