Chapter 5 Configuring VLANs 65
■The Main Server is a high-use server that needs to be accessed from all VLANs
and IP subnets. The server has an Sun GigaSwift Ethernet 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 VLANs1, 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
severis able to communicate onall 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 VLANs1 and 2. The switch port connected to the server has tagging turned
off.
■Clients 1 and2 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. Taggingis not enabled on Client 3’s switch port.
■Client 4 is a member of VLAN3, and can communicate only with the servers.
Taggingis not enabled on Client 4’s switch port.
■Client 5 is a member of both VLANs 1 and 2, and has a Sun GigaSwift Ethernet
adapter installed. It is connected to switch port 10. Both the adapter and the
switch port are configured forVLANs 1 and 2 and have tagging enabled.
VLAN tagging is only required tobe 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), 4094 possible VLAN IDs can be selected. Only 512 unique IDs can be
used simultaneously.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.