LevelOne GSW-1290 Gigabit Layer2 SNMP Switch
all multicast groups residing within the range of ports specified above.
Forward Unregistered Groups
−
Instructs the switch to forward a multicast
packet whose destination is an unregistered multicast group residing
within the range of ports specified above.
Filter Unregistered Groups
−
Instructs the switch to filter any multicast
packets whose destination is an unregistered multicast group residing
within the range of ports specified above
VLANs
The Switch Web Manager’s VLANs sub-folder is divided into two main windows,
802.1Q Static VLANs
and
802.1Q Port Settings
. Each is described after a short overview of VLANs.
Understanding 802.1Q VLANs
This review of 802.1Q VLANs presents some basic background about how VLANs work according to the
IEEE 802.1Q standard. VLANs operate according to the same rules regardless of whether the Switching
environment is Layer 2 or Layer 3. The difference is primarily that in a Layer 3 Switch there is an added
capability of unique association between a VLAN and an IP interface or subnet group.
A VLAN is a collection of end nodes grouped by logic rather than physical location. End nodes that
frequently communicate with each other are assigned to the same VLAN, regardless of where they are
located physically on the network. Logically, a VLAN can be equated to a broadcast domain, because
broadcast packets are forwarded only to members of the VLAN on which the broadcast was initiated.
IEEE 802.1Q VLANs
Some relevant terms:
Tagging - The act of putting 802.1Q VLAN information into the header of a packet.
Untagging - The act of stripping 802.1Q VLAN information out of the packet header.
Ingress port - A port on a Switch where packets are flowing into the Switch and VLAN decisions must be
made.
Egress port - A port on a Switch where packets are flowing out of the Switch, either to another Switch or to
an end station, and tagging decisions must be made.
IEEE 802.1Q (tagged) VLANs are implemented on the GSW-1290 Switch. 802.1Q VLANs require tagging,
which enables the VLANs to span an entire network (assuming all Switches on the network are IEEE
802.1Q-compliant).
Any port can be configured as either
tagging
or
untagging
. The
untagging
feature of IEEE 802.1Q VLANs
allow VLANs to work with legacy Switches that don’t recognize VLAN tags in packet headers. The
tagging
feature allows VLANs to span multiple 802.1Q VLAN compliant Switches through a single
physical connection and allows Spanning Tree to be enabled on all ports and work normally.
802.1Q VLAN Packet Forwarding
Packet forwarding decisions are made based upon the following three types of rules:
Ingress rules – rules relevant to the classification of received frames belonging to a VLAN.
Forwarding rules between ports – decides filter or forward the packet
Egress rules – determines if the packet must be sent tagged or untagged.
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Содержание ProCon GSW-1290
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