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Intel® NetStructure™ ZT 8101 10/100 Ethernet Switch User’s Manual 35
Switch Management and Operating Concepts
VLANs
VLANs allow you to group some physical ports as if they were on the same LAN. VLANs can be
created either statically or dynamically:
• Static VLAN—This VLAN is manually configured on the switch.
• Dynamic VLAN—This VLAN uses GVRP (GARP VLAN Registration Protocol) to enable
ports to dynamically join a VLAN group.
VLANs reduce traffic because traffic between VLANs is restricted. Bridges forward unicast,
multicast, and broadcast traffic only on LAN segments that serve the VLAN to which the traffic
belongs.
The switch supports two kinds of VLANs:
• Port based VLAN—These VLANs are defined by the physical port connections to the switch
and are restricted to the number of ports in the switch. They use untagged frames.
• IEEE 802.1Q VLAN—These VLANS are based on a packet-tagging scheme. Packets may be
tagged or untagged. A tagged packet's membership in an 802.1Q VLAN is determined by a tag
that is inserted in the packet header by the switch or an end node indicating the VLAN number
that the packet belongs to. Untagged packets are treated as if they were in a port based VLAN,
where a connection to one of the switch's physical ports determines VLAN membership.
Physical ports can belong to only one VLAN as an untagged port, but can belong to more than
one 802.1Q VLAN as a tagged port.
Initially, all ports belong to a special VLAN called “default.” This default VLAN is a IEEE802.1Q
VLAN, which has the following unique characteristics:
• The name and the type fields are read-only.
• It cannot be deleted.
• All ports can be deleted from this VLAN.
• Its VID is 1, which cannot be changed.
All user-configured VLANs have the following characteristics:
• The size of VLAN name field is 32 bytes.
• Ingress checking defaults to on.
• Up to 32 static VLANs can be configured.
The switch supports a maximum of 255 VLANs (32 static, the rest dynamic).
Port-Based VLANs
A port-based VLAN is the easiest type to configure on the switch because you only need to specify
the following:
• VLAN name
• Member ports