Microsens MS453490M Management Guide - Manual (Page 152)

C HAPTER 5 | Interface Configuration
VLAN Trunking
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VLAN T RUNKING
Use the Interface > VLAN Trunking page to allow unknown VLAN groups to
pass through the specified interface.
CLI R EFERENCES
◆ "vlan-trunking" on page 793
C OMMAND U SAGE
◆ Use this feature to configure a tunnel across one or more intermediate
switches which pass traffic for VLAN groups to which they do not
belong.
The following figure shows VLANs 1 and 2 configured on switches A and
B, with VLAN trunking being used to pass traffic for these VLAN groups
across switches C, D and E.
Figure 55: Configuring VLAN Trunking
Without VLAN trunking, you would have to configure VLANs 1 and 2 on
all intermediate switches – C, D and E; otherwise these switches would
drop any frames with unknown VLAN group tags. However, by enabling
VLAN trunking on the intermediate switch ports along the path
connecting VLANs 1 and 2, you only need to create these VLAN groups
in switches A and B. Switches C, D and E automatically allow frames
with VLAN group tags 1 and 2 (groups that are unknown to those
switches) to pass through their VLAN trunking ports.
◆ VLAN trunking can only be enabled on Gigabit Ethernet ports or trunks.
◆ VLAN trunking is mutually exclusive with the “access” switchport mode
(see "Adding Static Members to VLANs" on page 160 ). If VLAN trunking
is enabled on an interface, then that interface cannot be set to access
mode, and vice versa.
◆ To prevent loops from forming in the spanning tree, all unknown VLANs
will be bound to a single instance (either STP/RSTP or an MSTP
instance, depending on the selected STA mode).
◆ If both VLAN trunking and ingress filtering are disabled on an interface,
packets with unknown VLAN tags will still be allowed to enter this
interface and will be flooded to all other ports where VLAN trunking is
enabled. (In other words, VLAN trunking will still be effectively enabled
for the unknown VLAN).