User's Manual

MDS 05-6399A01, Rev. D MDS Master Station 47
mally only contains tagged traffic. If a VLAN trunk port receives an untagged packet, and the trunk is a
member of the native VLAN, that packet will be treated as if it came from the native VLAN. If the trunk
port is not a member of the native VLAN and an untagged packet arrives on that port, the packet will be
dropped.
As VLANs are implemented as bridges, and it is not valid for a bridge to be a member of another bridge,
it follows that a VLAN interface cannot be configured as a member of a bridge. VLANs can be config-
ured with IP addresses just as any other interface in the system.
Monitoring
As shown previously once VLANs are created they may be monitored on the Interface status screen the
same way physical interfaces appear:
5.6.4 Bridging
Understanding
The unit supports transparent bridging of LAN, and in firmware versions of 3.0.0 and higher, WiFi and
SD networks. The bridge forwards traffic between LAN interfaces and wireless interfaces at the layer-2 of
OSI model. This allows LAN and wireless clients to be in the same IP sub-network.
The bridge learns the clients’ locations by analyzing the source address of incoming frames from all at-
tached networks. For example, if a bridge sees a frame arrive on LAN port from Host A, the bridge con-
cludes that Host A can be reached through the segment connected to LAN port. Through this process, the
bridge builds a forwarding table (the learning process). When a frame is received on one of the bridge's
interfaces, the bridge looks up the frame's destination address in its forwarding table. If the table contains
an association between the destination address and any of the bridge's ports aside from the one on which
the frame was received, the frame is forwarded out the indicated port. If no association is found, the frame
is flooded to all ports except the inbound port. Broadcasts and multicast also are flooded in this way.
The bridged network is addressable via the ‘bridge’ interface (a virtual interface). The interfaces that are
in the bridge are called bridged interfaces. The interfaces that are not in the bridge are called routed inter-
faces. Bridging is performed between bridged interfaces. Routing is performed between routed interfaces.
The bridge interface itself is a routed interface.