H3C Technologies H3C S3600 Series Switches - Manual (Page 106)

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Table 1-2 Packet processing of a trunk port
Processing of an incoming packet
For an untagged packet For a tagged packet
Processing of an outgoing
packet
z If the port has already been
added to its default VLAN, tag
the packet with the default
VLAN tag and then forward
the packet.
z If the port has not been added
to its default VLAN, discard
the packet.
z If the VLAN ID is one of the
VLAN IDs allowed to pass
through the port, receive the
packet.
z If the VLAN ID is not one of
the VLAN IDs allowed to
pass through the port,
discard the packet.
z If the VLAN ID is just the
default VLAN ID, strip off
the tag and send the
packet.
z If the VLAN ID is not the
default VLAN ID, keep
the original tag
unchanged and send the
packet.
Table 1-3 Packet processing of a hybrid port
Processing of an incoming packet
For an untagged packet For a tagged packet
Processing of an outgoing
packet
z If the port has already been
added to its default VLAN,
tag the packet with the
default VLAN tag and then
forward the packet.
z If the port has not been
added to its default VLAN,
discard the packet.
z If the VLAN ID is one of the
VLAN IDs allowed to pass
through the port, receive the
packet.
z If the VLAN ID is not one of
the VLAN IDs allowed to
pass through the port,
discard the packet.
Send the packet if the VLAN ID
is allowed to pass through the
port. Use the port hybrid vlan
command to configure whether
the port keeps or strips off the
tags when sending packets of a
VLAN (including the default
VLAN).
Protocol-Based VLAN
Introduction to Protocol-Based VLAN
Protocol-based VLAN is also known as protocol VLAN, which is another way to classify VLANs.
Through the protocol-based VLANs, the switch can analyze the received packets carrying no VLAN tag
on the port and match the packets with the user-defined protocol template automatically according to
different encapsulation formats and the values of specific fields. If a packet is matched, the switch will
add a corresponding VLAN tag to it automatically. Thus, data of specific protocol is assigned
automatically to the corresponding VLAN for transmission.
This feature is used for binding the ToS provided in the network to VLAN to facilitate management and
maintenance.
Encapsulation Format of Ethernet Data
This section introduces the common encapsulation formats of Ethernet data for you to understand the
procedure for the switch to identify the packet protocols.
Ethernet II and 802.2/802.3 encapsulation
There are two encapsulation types of Ethernet packets: Ethernet II defined by RFC 894 and
802.2/802.3 defined by RFC 1042. The two encapsulation formats are described in the following
figures.
Ethernet II packet: