Sun Microsystems 806-2989-10 manual Configuring VLANs

FIGURE 5-2

■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).

shows the Ethernet Tag Header format.

Chapter 5 Configuring VLANs 47