Zte zxmsg 5200 Technical Manual page 52

ZXMSG 5200 (V2.0.2) Multiplex Service Gateway Technical Manual
Communication
VLAN Tag
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traditional LAN restricts the sites to its physical network. Figure
16 shows the basic VLAN adds another tag to the normal
Ethernet frame.
F 1 6 – V L A N C
I G U R E O N C E P T
The communications between VLANs are through access and
trunk link.
Access link:
An access link is a member of only one VLAN. In most case,
access link is linked with the client station.
Trunk link:
Trunk link is also called Tagged Link, This kind of port can
support multi-VLAN communication. A trunk link is capable of
carrying multiple VLANs. The data frames on the trunk link
are identified by using indicator.
Explicit and implicit tag:
When frames are transmitted on network, a mean is required to
identify the VLAN to which a frame belongs. The mean is to add
VLAN tags. Switch sends the frame only to its belonging VLAN.
When a bridge receives data, it labels the data with a VLAN tag
to indicate the data source. This tag is called explicit tag.
Implicit tag mode is used for specific VLAN source for the data.
With implicit tag, data is not tagged and source VLAN of data is
specified in other modes (for example the port).
Tag header:
The frame with a tag is called a tag frame, it has a tag
header. Figure 17 shows the tag header format, including
two-byte Tag Protocol Identifier (TPID) and two-byte Tag