Sun Microsystems GigaSwift Ethernet Adapter - Manual (Page 88)

66 Sun GigaSwift Ethernet Adapter Installation and User’s Guide • August 2004
Configuring VLANs
VLANs can be created according to various criteria, but each VLAN must be
assigned a VLAN tag or VLAN ID (VID). The VID is a 12-bit identifier between 1
and 4094 that identifies a unique VLAN. For each network interface (
ce0 , ce1 , ce2
and so on), 4094 possible VLAN IDs can be selected. Because IP subnets are
commonly used, it is best to use IP subnets when setting up a VLAN network
interface. This means that each VID assigned to a VLAN interface of a physical
network interface will belong to different subnets.
Tagging an Ethernet frame requires the addition of a tag header to the frame. The
header is inserted immediately following the Destination MAC address and the
Source MAC address. The tag header consists of two bytes of Ethernet Tag Protocol
Identifier (TPID, 0x8100) and two bytes of Tag Control Information (TCI).
FIGURE 5-2
shows the Ethernet Tag Header format.
FIGURE 5-2 Ethernet Tag Header Format
By default, a single VLAN is configured for every port, which groups all ports into
the same broadcast domain, just as if there were no VLANs at all, VLAN tagging for
the switch port turned off.
Note – If you configure a VLAN virtual device for an adapter, all traffic sent or
received by that adapter must be in VLAN-tagged format.
TPID (0x8100
3 bits 1
bit
12 bytes
User_priority CFI VID
Octet
1
2
3
4