Antaira Technologies
– Enterprise Managed Media Converter
FCN-3112 Series User Manual V1.0
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frames entering that port (ingress traffic). On the other hand, a port can be defined as a member of
multiple VLAN (multiple VID). These VIDs constitute an access list for the port. The access list can be
used to filter tagged ingress traffic (the converter will drop a tagged packet if that tagged packet does
not have a VID that belong to the set of VIDs assigned to that port). The converter also consults the
access list to filter packets it sends to that port (egress traffic). Packets will not be forwarded unless
the VID associated with that packet belongs to the set of VIDs assigned to that port.
The differences between Ingress and Egress configurations can provide network segmentation.
Moreover, they allow resources to be shared across more than one VLAN.
Important VLAN Definitions
Ingress
The point at which a frame is received on a port and the decisions must be made. The converter
examines the VID (if present) in the received frames header and decides whether or not and where to
forward the frame. If the received frame is untagged, the converter will tag the frame with the PVID for
the port on which it was received. It will then use traditional Ethernet bridging algorithms to determine
the port to which the packet should be forwarded.
Next, it checks to see if each destination port is on the same VLAN as the PVID and thus can transmit
the frame. If the destination port is a member of the VLAN used by the ingress port, the frame will be
forwarded. If the received frame is tagged with VLAN information, the converter checks its address
table to see whether the destination port is a member of the same VLAN. Assuming both ports are
members of the tagged VLAN, the frame will be forwarded.
Ingress Filtering
The process of checking an incoming frame and comparing its VID with the ingress port VLAN
membership is known as Ingress Filtering.
On the media converter, it can be either enabled or disabled
.
1. When an untagged frame is received, the ingress port PVID will be applied to the frame.
2. When a tagged frame is received, the VID in the frame tag is used.
When Ingress Filtering is “enabled”, the media converter will first determine.
1. If the ingress port itself is a member of the frame VLAN, it will receive the frame.
2. If the ingress
port is not a member of the frame VLAN, the frame will be dropped.
3. If it is a member of that VLAN, the media converter then checks its address table to see
whether the destination port is a member of the same VLAN. Assuming both ports are
members of that VLAN, the frame will be forwarded.
Administrators should make sure
that each port’s PVID is set up; otherwise, incoming frames may be
dropped if Ingress Filtering is enabled. On the other hand, when Ingress Filtering is disabled, the
media converter will not compare the incoming frame VID with the ingress port VLAN membership. It
will only check its address table to see whether the destination VLAN exists.
1. If the VLAN is unknown, it will be broadcasted.
2. If the VLAN and the destination MAC address are known, the frame will be forwarded.
3. If the VLAN is known and the destination MAC address is unknown, the frame will be flooded
to all ports in the VLAN.
Tagging
Every port on an 802.1Q compliant converter can be configured as tagging or un-tagging
.
Ports with
tagging Enabled will put the VID number, priority and other VLAN information into the header of all
packets that flow into and out of it. If a packet has been tagged previously, the port will not alter the
