Xerox NS-2260 - Manual (Page 19)

1.5.6.2 IEEE 802.1Q VLAN (Tag-based VLAN)
Tag-based VLAN is an IEEE 802.1Q specification standard. Therefore, it is possible to create a VLAN
across devices from different venders. IEEE 802.1Q VLAN uses a technique to insert a tag into the
Ethernet frames. Tag contains a VLAN Identifier (VID) that indicates the VLAN numbers.
The switch can classify each received packet as belonging to one and only one VLAN. If the received
packet is VLAN-tagged, the packet is classified as belonging to the VLAN specified in the VLAN tag
header. If the received packet is untagged, it is classified as belonging to the default VLAN configured for
the ingress port.
Required configurations:
_ Enable or disable GVRP support
_ VLAN information including VID (2-4094) and name
_ Tagged member ports of each VLAN
_ Outgoing tag mode for each member port
Tag - outgoing frames with VLAN-tagged
Untag - outgoing frames without VLAN-tagged
_ PVID (Port VID, 1-255 for untagged incoming frames) for each port
_ Ingress Rule 1 setting for each port : forward only packets with VID
matching configured PVID
_ Ingress Rule 2 setting for each port : drop untagged frames
PVID : this feature is useful to accommodate the devices which do not support tagging to participate in the
VLAN.
GVRP - GARP [Generic Attribute Registration Protocol] VLAN Registration Protocol : GVRP
allows automatic VLAN configuration between the switch and n odes. If the switch is connected to a device
with GVRP enabled, you can send a GVRP request using the VID of a VLAN defined on the switch, the
switch will automatically add that device to the existing VLAN. (GVRP - 802.1Q compliant, GARP -
802.1P compliant)
1.5.6.3 Protocol-based VLAN
In order for an end station to send packets to different VLANs, it itself has to be either capable of tagging
packets it sends with VLAN tags or attached to a VLAN-aware bridge that is capable of classifying and
tagging the packet with different VLAN ID based on not only default PVID but also other information
about the packet, such as the protocol. The switch can support 802.1v compliant protocol-based VLAN
classification by means of both built -in knowledge of layer 2 packet formats used by selected popular
protocols, such as Novell IPX and AppleTalk`s EtherTalk, and others. Required configuration:
_ Protocol setting for each VLAN group defined in 802.1Q VLAN mode
_ If more than two VLAN groups are configured with same protocol
value, make sure the member ports of those groups are not overlaping.
Any incoming untagged packet is checked and classified according the Protocol vs. VLAN mapping
settings. If an associated VLAN group is found, the packet is calssified and is inserted with VID tag of the
group VLAN ID instead of input port PVID.
1.5.7 Spanning Tree Protocol
Spanning-Tree Protocol (STP) is a link management protocol that provides path redundancy while
preventing undesirable loops in the network. For an Ethernet network to function properly, only one active
path must exist between two stations. Multiple active paths between stations cause loops in the network. If
a loop exists in the network, you might receive duplicate messages. When loops occur, some switches see
stations on both sides of the switch. This condition confuses the forwarding algorithm and allows duplicate
frames to be forwarded.