Enterasys Networks 5H1XX, 5G1XX manual Vlan Configuration

VLAN Configuration

B.2 VLAN CONFIGURATION

VLAN operation on the switch is enabled by default. Therefore, all frames are transferred internally through the switch with a VLAN tag. This tag may already be on the frame entering the switch, or added to the frame by the switch. VLAN information already existing on frames entering the switch is automatically handled by the switch. The switch learns VLAN information from tagged frames and appropriately switches frames out the proper ports based on this information. The configuration of VLANs for frames entering the switch without tags must be made by the user of the switch. This configuration can be made either through the console interface or via SNMP.

Assigning Ports to VLANs

Before enabling VLANs for the switch, you must first assign each port to the VLAN groups it will participate in. By default, all ports are assigned to VLAN 1 as untagged ports. You should add a port as a tagged port (that is, a port attached to a VLAN-aware device) if you want it to carry traffic for one or more VLANs and the device at the other end of the link also supports VLANs. Then assign the port at the other end of the link to the same VLANs. However, if you want a port on this switch to participate in one or more VLANs, but the device at the other end of the link does not support VLANs, then you must add this port as an untagged port (that is, a port attached to a VLAN-unaware device).

Port-based VLANs are tied to specific ports. The switch’s forwarding decision is based on the destination MAC address and its associated port. Therefore, to make valid forwarding and flooding decisions, the switch learns the relationship of the MAC address to its related port—and thus to the VLAN—at run-time.

VLAN Classification

When the switch receives a frame, it classifies the frame in one of two ways:

•If the frame is untagged, the switch assigns the frame to an associated VLAN based on the PVID of the receiving port.

•If the frame is tagged, the switch uses the tagged VLAN ID to identify the port broadcast domain of the frame.

Port Overlapping

Port overlapping can be used to allow access to commonly shared network resources among different VLAN groups, such as file servers or printers. Note that if you implement VLANs which do not overlap, but still need to communicate, you must connect them using a router or Layer 3 switch.

B-2Virtual LANs (VLANs)