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Publication date: January, 2005
Revision A1
43
Ingress Rule:
Each packet received by a VLAN-aware bridge will be classified to a VLAN.
The classification rule is described as follows.
1. If the VID of the packet is null VID (VID=0)or this packet is an untagged packet:
If there are still some other ways(e.g. protocol, MAC address, application, IP-
subnet, etc.) to classify the incoming packets beside port-based classification in
implement and these approaches can offer non-zero VID, then, use the value of VID
offered by other classifications for VLAN’s classification.
If there is only port-based classification in implement or other classification
approaches cannot offer non-zero VID for the incoming packets, then assign the
PVID to the incoming packets as VID for the classification of the VLAN group.
2. If the VID is not a null VID (VID≠0), then use the value to classify the VLAN group.
Egress Ru le :
An egress list is used to make the tagging and forwarding decision on an
outgoing port. It specifies the VLANs whose packets can be transmitted out and
specifies if the packet should be tagged or not. It can be configured for port’s VLAN
membership, and tagged or untagged for a transmitted packet. When a packet is
transmitted out, the VLAN bridge checks the port’s egress list. If the VLAN of the
packet is on the egress list of the port on which the packet transmits out, the packet
will be transmitted with the priority accordingly. If enabled, an egress port will
transmit out a tagged packet if the port is connected to a 802.1Q-compliant devi ce.
If an egress port is connected to a non-802.1Q device or an end station, VLAN
bridge must transmit out an untagged packet, i.e. the tag has been stripped off in an
egress port. Egress rule can be set by per port.
Independent VLAN Learning (IVL):
It specifies the mode how to learn MAC address. For a specified VLAN, it will
use an independent filtering database (FID) to learn or look up the membership
information of the VLAN and decide where to go.
Shared VLAN Learning (SVL):
It specifies the mode how to learn MAC address. In this mode, some VLAN
or all VLANs use the same filtering database storing the membership information of
the VLAN to learn or look up the membership information of the VLAN. In 16 Gigabit
Web Smart Switch, you can choose a VID for sharing filtering database in Shared
VID field if you wish to use the existed filtering database. For a specified VLAN,
when a MAC address is learned by a switch, VLAN will use this formation to make
forwarding decision.
Filtering Database:
Referred to as FID. It can provide the information where the packet will be
sent to. Filtering database will supply the outgoing port according to the request
from forwarding process with VID and DA. When a packet is received, if it has a
non-zero VID, then FID will offer the associated outgoing ports information to the
packet.
In SVL, VLANs use the same Filtering Database. In IVL, VLANs use different
FIDs. Any VID can be assigned to the same FID by administrator.