Rules Of Vlan Operation; Ingress Rules - 3Com corebuilder 3500 Implementation Manual

Rules of VLAN
Operation

Ingress Rules

After you select a VLAN mode for the system and create VLAN interfaces
with VLAN characteristics such as IEEE 802.1Q or no tagging, port
membership, protocol type, and Layer-3 (network) address information,
the system determines the details of VLAN operation by observing two
main types of rules:
Ingress rules — Assign an incoming frame to a specific VLAN.
Egress rules — Use standard bridging rules to determine whether the
frame is forwarded, flooded, or filtered. These rules also determine
the tag status of the transmitted frame.
These rules are classified in the IEEE 802.1Q standard. In addition, the
system relies on some system-specific rules.
These rules determine the VLAN to which an incoming frame belongs.
The frame is assigned to the VLAN that has the most specific match. The
system uses this protocol match hierarchy to find the most specific match:
1 IEEE 802.1Q tag VID value, if the frame is tagged
2 A specific protocol match (for example, IP, IPX, or AppleTalk)
3 Either the default VLAN (an untagged, unspecified protocol type VLAN
with all ports and a VID of 1) or any VLAN that has the unspecified
protocol type
4 The null VLAN, a special VLAN that the system uses if the frame cannot
be assigned to any VLAN. This VLAN has no ports and has no address
table (in allClosed mode).
The CoreBuilder 3500 Release 3.0 ingress rules are classified according to
the tag status of the frame and the VLAN mode (allOpen for open VLANs
or allClosed for closed VLANs). For the ingress rules, the system considers
a priority tagged frame to be an untagged frame.

Rules of VLAN Operation

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