Vlan Types; Port-Based Vlan - HP FlexNetwork NJ5000 User Manual

IEEE 802.1Q inserts a four-byte VLAN tag after the DA&SA field, as shown in
Figure 115 Position and format of VLAN tag
A VLAN tag contains the following fields:
•
Tag protocol identifier (TPID)—The 16-bit TPID field indicates whether the frame is
VLAN-tagged and is 0x8100 by default.
•
Priority—The 3-bit priority field indicates the 802.1p priority of the frame.
•
Canonical format indicator (CFI)—The 1-bit CFI field specifies whether the MAC addresses
are encapsulated in the standard format when packets are transmitted across different media. A
value of 0 indicates that MAC addresses are encapsulated in the standard format. The value of
1 indicates that MAC addresses are encapsulated in a non-standard format. The value of the
field is 0 by default.
•
VLAN ID—The 12-bit VLAN ID field identifies the VLAN the frame belongs to.
A network device handles an incoming frame depending on whether the frame is VLAN tagged and
the value of the VLAN tag, if any.
The Ethernet II encapsulation format is used in this section. In addition to the Ethernet II
encapsulation format, Ethernet also supports other encapsulation formats, including 802.2 LLC,
802.2 SNAP, and 802.3 raw. The VLAN tag fields are added to frames encapsulated in these formats
for VLAN identification.
When a frame carrying multiple VLAN tags passes through, the device processes the frame
according to its outer VLAN tag, and transmits the inner tags as payload.

VLAN types

You can implement VLANs based on the following criteria:
•
Port
•
MAC address
•
Protocol
•
IP subnet
•
Policy
•
Other criteria
The Web interface is available only for port-based VLANs, and this chapter introduces only
port-based VLANs.

Port-based VLAN

Port-based VLANs group VLAN members by port. A port forwards traffic for a VLAN only after it is
assigned to the VLAN.
Port link type
You can configure the link type of a port as access, trunk, or hybrid. The link types use the following
VLAN tag handling methods:
•
Access port—An access port belongs to only one VLAN and sends traffic untagged. It is
usually used to connect a terminal device unable to identify VLAN tagged-packets or when it is
107
Figure 115.