3Com 9100 manual AccountingEngineering

Types of VLANs 69

AccountingEngineering

Switch 1

Switch 2

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Figure 9 Two port-based VLANs spanning two Switch 9100 devices

VLAN Accounting spans Switch 1 and Switch 2 by way of a connection between Switch 1, port 1 and Switch 2, port 3. VLAN Engineering spans Switch 1 and Switch 2 by way of a connection between Switch 1, port 5, and Switch 2, port 6.

Using the configuration described above, you can create multiple VLANs that span multiple switches, in a daisy-chained fashion. Each switch must have a dedicated port for each VLAN. Each dedicated port must be connected to a port that is a member of its VLAN on the next switch.

Tagged VLANs Tagging is a process that inserts a marker (called a tag) into the Ethernet frame. The tag contains the identification number of a specific VLAN, called the VLANid.

The use of 802.1Q tagged packets may lead to the appearance of packets slightly bigger than the current IEEE 802.3/Ethernet maximum of 1,518 bytes. This may affect packet error counters in other devices, and may also lead to connectivity problems if non-802.1Q bridges or routers are placed in the path.