VLAN Switch is a forwarding method that forwards data according
to the information in VLAN tags of received frames. This method requires
a pre-configured static forwarding path along switching nodes on the
network. When receiving VLAN-tagged frames matching VLAN Switch entries,
a switching node forwards the frames to the interfaces manually specified
in the VLAN Switch table. VLAN Switch improves device forwarding efficiency
and security, and prevents MAC address attacks as well as broadcast
storms.
VLAN Switch includes two sub-functions: switch-vlan and stack-vlan.
Stack-vlan
Similar to the VLAN stacking function, the stack-vlan function is
a Layer 2 feature that adds an outer VLAN tag to each frame, and decides
which outer VLAN tags to be added to frames depending on information
in the original VLAN tags carried in the frames. Table 6-1 lists the comparison
between VLAN stacking and stack-vlan. For details about VLAN stacking,
see Selective QinQ.
Table 6-1 Comparison between stack-vlan and VLAN stacking
Function
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Similarities
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Differences
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Advantages and Disadvantages
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Stack-vlan
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VLAN Switch requires a pre-configured static forwarding
path along switching nodes on the network. When receiving VLAN-tagged
frames matching VLAN Switch entries, a switching node forwards the
frames to the interfaces manually specified in the VLAN Switch table.
The VLANs used in VLAN Switch cannot be created in the
system view.
|
Advantage:
Switching nodes forward frames without searching
for the MAC address table, which improves forwarding efficiency and
network security, and prevents MAC address attacks as well as broadcast
storms.
Disadvantage:
If a large number of user devices connect
to a switching node, the network administrator needs to configure
a VLAN Switch entry for each user device on the switching node to
establish a static forwarding path. This increases the network administrator's
workload and complicates network management.
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VLAN stacking
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Frames are forwarded after looking up the entries in the
MAC address table.
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Advantage:
The administrator does not need to specify
a static forwarding path, thereby simplifying user access. Frames
are forwarded according to the information in the MAC address table.
Disadvantage:
Device forwarding efficiency is low, and
the network is prone to broadcast storms and MAC address attacks.
|
Switch-vlan
Similar to the VLAN mapping function, the switch-vlan function
implements inter-VLAN communication. Table 6-2 lists the comparison
between VLAN mapping and switch-vlan. For details about VLAN mapping,
see Principles.
Table 6-2 Comparison between switch-vlan and VLAN mapping
Function
|
Similarities
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Differences
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Advantages and Disadvantages
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Switch-vlan
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After receiving a VLAN-tagged frame, an interface replaces
the outer VLAN tag of the frame.
Before sending a frame to another VLAN, an interface configured
with VLAN mapping or switch-vlan replaces the VLAN tag of the frame
with the destination VLAN tag.
After receiving a frame from another VLAN, an interface replaces
the VLAN tag of the frame with the local VLAN tag.
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VLAN Switch requires a pre-configured static forwarding
path along switching nodes on the network. When receiving VLAN-tagged
frames matching VLAN Switch entries, a switching node forwards the
frames to the interfaces manually specified in the VLAN Switch table.
The VLANs used in VLAN Switch cannot be created in
the system view.
|
Advantage:
Switching nodes forward frames without searching
for the MAC address table, which improves forwarding efficiency and
network security, and prevents MAC address attacks as well as broadcast
storms.
Disadvantage:
If a large number of user devices connect
to a switching node, the network administrator needs to configure
a VLAN Switch entry for each user device on the switching node to
establish a static forwarding path. This increases the network administrator's
workload and complicates network management.
|
VLAN mapping
|
A switch configured with VLAN mapping forwards frames according
to the MAC address table.
VLAN mapping requires that IP addresses
of devices in both VLANs be on the same network segment.
|
Advantage:
The administrator does not need to specify
a static forwarding path, thereby simplifying user access. Frames
are forwarded according to the information in the MAC address table.
Disadvantage:
Device forwarding efficiency is low, and
the network is prone to broadcast storms and MAC address attacks.
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