3Com Switch 4800G 24-Port Configuration Manual page 88

88 C 9: VLAN C
HAPTER
n
Configuring an
Access-Port-Based VLAN
ONFIGURATION
Default VLAN
You can configure the default VLAN for a port. By default, VLAN 1 is the default
VLAN for all ports. However, this can be changed as needed.
An Access port only belongs to one VLAN. Therefore, its default VLAN is the
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VLAN it resides in and cannot be configured.
You can configure the default VLAN for the Trunk port or the Hybrid port as
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they can both belong to multiple VLANs.
After deletion of the default VLAN using the undo vlan command, the default
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VLAN for an Access port will revert to VLAN 1, whereas that for the Trunk or
Hybrid port remains, meaning the port can use a nonexistent VLAN as the
default VLAN.
For a port in automatic voice VLAN mode, do not set the voice VLAN as the default
VLAN of the port. Otherwise, the system prompts error information. For
information about voice VLAN, refer to "Voice VLAN Configuration" on page 99.
Configured with the default VLAN, a port handles packets in the following ways:
Inbound packets handling
If no tag is
carried in the
Port type packet
Access Port Tag the packet
with the default
VLAN ID
Trunk port Check whether the
default VLAN ID of
the port is in the
list of VLANs
allowed to pass
through the port, if
yes, tag the packet
with the default
VLAN ID; if no,
discard the packet
Hybrid port
There are two ways to configure Access-port-based VLAN: one way is to configure
in VLAN view, the other way is to configure in Ethernet port view/port group view.
Follow these steps to configure the Access-port-based VLAN in VLAN view:
If a tag is carried in the
packet
Receive the packet if
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its VLAN ID is the same
as the default VLAN ID
Discard the packet if
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its VLAN ID is different
from the default VLAN
ID
Receive the packet if
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the VLAN ID is in the
list of VLANs allowed
to pass through the
port
Discard the packet if
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the VLAN ID is not in
the list of VLANs
allowed to pass
through the port
Outbound packets
handling
Strip the Tag and send the
packet as the VLAN ID is
the same with the default
VLAN ID
Strip the tag and send
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the packet if the VLAN
ID is the same as the
default VLAN ID
Keep the tag and send
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the packet if the VLAN
ID is not the same as
the default VLAN ID
but allowed to pass
through the port
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 the tags when
sending packets of a
VLAN (including the
default VLAN).
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