24-port NWay Ethernet Switch User’s Guide
Switch Management and Operating Concepts
65
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.
Layer 3-Based VLANs
Layer 3-based VLANs use network-layer addresses (subnet
address for TCP/IP) to determine VLAN membership. These
VLANs are based on layer 3 information, but this does not
constitute a ‘routing’ function.
Note:
The DES-3326 allows an IP subnet to be configured
for each 802.1Q VLAN that exists on the switch.
Содержание DES-3326
Страница 29: ...24 port NWay Ethernet Switch User s Guide Introduction 13 ...
Страница 289: ...24 port NWay Ethernet Switch User s Guide Web Based Network Management 273 ...
Страница 394: ...24 port NWay Ethernet Switch User s Guide 378 Understanding and Troubleshooting the Spanning Tree Protocol ...
Страница 396: ...24 port NWay Ethernet Switch User s Guide 380 Understanding and Troubleshooting the Spanning Tree Protocol ...
Страница 398: ...24 port NWay Ethernet Switch User s Guide 382 Understanding and Troubleshooting the Spanning Tree Protocol ...
Страница 400: ...24 port NWay Ethernet Switch User s Guide 384 Understanding and Troubleshooting the Spanning Tree Protocol ...
Страница 402: ...24 port NWay Ethernet Switch User s Guide 386 Understanding and Troubleshooting the Spanning Tree Protocol ...
Страница 414: ...24 port NWay Ethernet Switch User s Guide 398 Understanding and Troubleshooting the Spanning Tree Protocol ...
Страница 425: ......