Sun Microsystems 806-2989-10 - Manuel (Page 67)

Chapter 5 Configuring VLANs 47
■
The Main Server is a high-use server that needs to be accessed from all VLANs
and IP subnets. The server has an Sun GigabitEthernet adapter installed. All three
IP subnets are accessed via the single physical adapter interface. The server is
attached to one of the SunSwitch’s Gigabit Ethernet ports, which is configured for
VLANs 1, 2, and 3. Both the adapter and the connected SunSwitch port have
tagging turned on. Because of the tagging VLAN capabilities of both devices, the
sever is able to communicate on all three IP subnets in this network, but continues
to maintain broadcast separation between all of them.
■ The Accounting Server is available to VLAN 3 only. It is isolated from all traffic
on VLANs 1 and 2. The switch port connected to the server has tagging turned
off.
■ Clients 1 and 2 are attached to a shared media hub that is then connected to the
switch. They belong to VLAN 2 only, and are logically in the same IP subnet as
the Main Server and Client 5. The switch port connected to this segment has
tagging turned off.
■ Client 3 is a member of VLAN 1, and can communicate only with the Main Server
and Client 5. Tagging is not enabled on Client 3’s switch port.
■ Client 4 is a member of VLAN 3, and can communicate only with the servers.
Tagging is not enabled on Client 4’s switch port.
■ Client 5 is a member of both VLANs 1 and 2, and has a Sun GigabitEthernet
adapter installed. It is connected to switch port 10. Both the adapter and the
switch port are configured for VLANs 1 and 2 and have tagging enabled.
VLAN tagging is only required to be enabled on switch ports that create trunk links
to other VLAN-aware Ethernet switches, or on ports connected to tag-capable end-
stations, such as servers or workstations with VLAN-aware adapters.
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), 512 possible VLANs can be created. Because IP subnets are commonly
used, it’s 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.