Using VLANs

VLANs enable grouping users by logical function instead of physical location. They make managing bandwidth usage within networks possible by:

  • Allowing grouping of high-bandwidth users on low-traffic segments

  • Organizing users from different LAN segments according to their need for common resources and individual protocols

  • Improving traffic control at the edge of networks by separating traffic of different protocol types.

  • Enhancing network security by creating subnets to control in-band access to specific network resources.

This chapter describes static VLANs configured for port-based or protocol-based operation.

Static VLANs are configured with a name, VLAN ID number (VID) and port members. For dynamic VLANs, see GVRP. 802.1Q compatibility enables you to assign each switch port to multiple VLANs.

Some recommended steps to take for using VLANs:

  1. Plan your VLAN strategy and create a map of the logical topology. Include consideration for the interaction between VLANs and other features such as Spanning Tree Protocol, port trunking and IGMP. See Effects of VLANs on other switch features. If you plan on usingdynamic VLANs, include the port configuration planning necessary to support this feature, see GVRP.

    By default, the switches covered in this guide are 802.1Q VLAN-enabled, allow for up to 256 static VLANs and 2048 total static and dynamic VLANs.

  2. Configure at least one VLAN in addition to the default VLAN.

  3. Assign the desired switch ports to the new VLANs.

  4. If you are managing VLANs with SNMP in an IP network, the VLAN through which you are managing the switch must have an IP address. For information on the procedure and restrictions when you configure an IP address on a VLAN interface, see Comparative operation of port based and protocol based VLANs.