Allied Telesis Rapier i AT-RP16Fi/SC, Руководство пользователя

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82 Rapier Switch User Guide
Software Release 2.6.1
C613-02025-00 REV C
Generic VLAN Registration Protocol
(GVRP)
The GARP application GVRP allows switches in a network to dynamically
share VLAN membership information, to reduce the need for statically
configuring all VLAN membership changes on all switches in a network. See
the
Generic Attribute Registration Protocol (GARP) chapter in the Rapier Switch
Software Reference .
Layer 2 Switching Process
The Layer 2 switching process comprises related but separate processes. The
Ingress Rules admit or discard frames based on their VLAN tagging. The
Learning Process learns the MAC addresses and VLAN membership of frames
admitted on each port. The Forwarding Process determines which ports the
frames are forwarded to, and the Quality of Service priority with which they are
transmitted. Finally, the Egress Rules determine for each frame whether VLAN
tags are included in the Ethernet frames that are transmitted. These processes
assume that each station on the extended LAN has a unique data link layer
address, and that all data link layer frames have a header which includes the
source (sender’s) MAC address and destination (recipient’s) MAC address.
The Ingress Rules
When a frame first arrives at a port, the Ingress Rules for the port check the
VLAN tagging in the frame to determine whether it will be discarded or
forwarded to the Learning Process.
The first check depends on whether the Acceptable Frame Types parameter is set
to Admit All Frames or to Admit Only VLAN Tagged Frames . A port that transmits
only VLAN tagged frames, regardless of which VLAN the port belongs to, will
be automatically set to Admit Only VLAN Tagged Frames. The user cannot
change this setting. Frames with a null numerical VLAN Identifier (VID) are
VLAN-untagged frames, or frames with priority tagging only.
Every frame received by the switch must be associated with a VLAN. If a frame
is admitted by the Acceptable Frame Types parameter, the second part of the
Ingress Rules associates each untagged frame admitted with the VID of the
VLAN for which the port is untagged.
Every port belongs to one or more VLANs, and therefore every incoming
frame will have a VID to show which VLAN it belongs to. The final part of the
Ingress Rules depends on whether
Ingress Filtering is enabled for the port. If
Ingress Filtering is disabled, all frames are passed on to the Learning Process,
regardless of which VLAN they belong to. If Ingress Filtering is enabled,
frames are admitted only if they have the VID of a VLAN to which the port
belongs. If they have the VID of a VLAN to which the port does not belong,
they are discarded.