802.1
There
switch
Understand nomenclature of the Switch
Tagging and Untagging
Every port on an 802.1Q compliant switch can be configured as tagging or untagging.
。
Tagging:
Ports with tagging enabled will put the VID number, priority and other VLAN information
into the header of all packets that flow into those ports. If a packet has previously been tagged, the
port will not alter the packet, thus keeping the VLAN information intact. The VLAN information in
nt devices on the network to make
。
nformation.
Here pay attention to the explainion of
“Access”
and
“Trunk”
.
。
Access:
Ports will strip the 802.1Q tag from all packets that out of those ports. If the packet doesn’t
have an 802.1Q VLAN tag, the port will not alter the packet. Thus, all packets received by and
y an untagging port will have no 802.1Q VLAN information. Untagging is used to send
nto
rt
e used by other 802.1Q compliant devices on the network to make packet forwarding
Port VID (PVID)
Set the port VLAN ID that will be assigned to untagged traffic on a given port. This feature is useful for
accommodating devices that you want to participate in the VLAN but that don’t support tagging. The
Q VLAN
are up to 256 configurable VLAN groups. By default when 802.1Q is enabled, all ports on the
belong to default VLAN (VID 1). The default VLAN cannot be deleted.
the tag can then be used by other 802.1Q complia
packet-forwarding decisions.
Untagging:
Ports with untagging enabled will strip the 802.1Q tag from all packets that flow into
those ports. If the packet doesn't have an 802.1Q VLAN tag, the port will not alter the packet. Thus,
all packets received by and forwarded by an untagging port will have no 802.1Q VLAN i
(Remember that the PVID is only used internally within the Switch). Untagging is used to send
packets from an 802.1Q-compliant network device to a non-compliant network device.
forwarded b
packets from an 802.1Q-compliant network device to a non-compliant network device.
。
Trunk:
Ports with tagging enabled will put the VID number, priority and other VLAN information i
the header of all packets that out of those ports. If a packet has previously been tagged, the po
will not alter the packet, thus keeping the VLAN information intact. The VLAN information in the tag
can then b
decisions.
