LevelOne ProCon GSW-1290, User Manual

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LevelOne GSW-1290 Gigabit Layer2 SNMP Switch
Ports with untagging enabled will strip the 802.1Q tag from all packets that flow into and out of those ports.
If the packet doesn’t have an 802.1Q VLAN tag, the port will not alter the packet. Thus, all packets
received by and forwarded by an untagging port will have no 802.1Q VLAN information. (Remember that
the PVID is only used internally within the Switch). Untagging is used to send packets from an 802.1Q-
compliant network device to a non-compliant network device.
Ingress Filtering
A port on a Switch where packets are flowing into the Switch and VLAN decisions must be made is
referred to as an
ingress port . If ingress filtering is enabled for a port, the Switch will examine the VLAN
information in the packet header (if present) and decide whether or not to forward the packet.
If the packet is tagged with VLAN information, the ingress port will first determine if the ingress port itself
is a member of the tagged VLAN. If it is not, the packet will be dropped. If the ingress port is a member of
the 802.1Q VLAN, the Switch then determines if the destination port is a member of the 802.1Q VLAN. If
it is not, the packet is dropped. If the destination port is a member of the 802.1Q VLAN, the packet is
forwarded and the destination port transmits it to its attached network segment.
If the packet is not tagged with VLAN information, the ingress port will tag the packet with its own PVID
as a VID (if the port is a tagging port). The Switch then determines if the destination port is a member of
the same VLAN (has the same VID) as the ingress port. If it does not, the packet is dropped. If it has the
same VID, the packet is forwarded and the destination port transmits it on its attached network segment.
This process is referred to as
ingress filtering and is used to conserve bandwidth within the Switch by
dropping packets that are not on the same VLAN as the ingress port at the point of reception . This
eliminates the subsequent processing of packets that will just be dropped by the destination port.
802.1Q Static VLANs
To create or modify an 802.1Q VLAN:
In the
Configuration folder, open the VLANs folder and click the Static VLAN Entry link to open the
following window:
Figure 4- 20. 802.1Q Static VLANs Entries table
The first 802.1Q Static VLANs window lists all previously configured VLANs by VLAN ID and name.
To delete an existing 802.1Q VLAN, click the corresponding Delete button.
To create a new 802.1Q VLAN, click the Add button. A new window appears, use this to configure the
port settings and to assign a unique name and number to the new VLAN. See the table below for a
description of the parameters in the new window.
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