Transparent VLAN


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2. Transparent VLAN

The VLAN tag (802.1Q protocol) is a 4B field in the Ethernet frame. It is inserted between the MAC address and EtherType/Length fields of the original frame.

The VLAN packet is defined by two main parameters:

VLAN tag

– VLAN Identifier (VID) is also called “VLAN number”. It is 12 bits long so we can have up to 4096 VLANs (0x0000 and 0xFFF values are reserved).

Priority Code Point (PCP)

– a 3bit field which refers to the IEEE 802.1p priority. It indicates the frame priority level. Possible values are from 0 (best effort) to 7 (highest priority); 1 represents the lowest priority. These values can be used to prioritize different traffic classes (voice, data, …).

See the following example:

VLAN diagram

Fig. 2.1: VLAN diagram

As you can see in Fig. 2.1, “VLAN diagram”, we have individual VLANs for Management and two distinct technologies, each with its own IP subnet.


You can combine the VLAN feature with a TCP proxy and Terminal Servers. See the respective help in the RipEX web interface for details.

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