N-Tron 9000 Series - Manual (Page 19)

5/17/2007 page 19 of 138
Virtual LAN
The switch provides support for setting up both tagged Virtual LANs and port based Virtual LANs.
A port may belong to any number of Virtual LANs. The VLAN membership of a station is determined by
the VLAN(s) that have been defined for the port to which the station is connected. If a station should move
from one port to another, it loses its current VLAN membership and inherits that of the new port it is
connected to.
A Default Virtual LAN exists to which a port, which is not a member of any other Virtual LAN, will
belong. This allows the switch to operate as a ‘normal’ Bridge when it is used in a network. A port is
automatically removed from the Default VLAN when it is reconfigured to belong to another Virtual LAN.
Using Tagged VLANs the switch has the ability to take non-tagged packets in some ports, add a
VLAN tag to the packet and send it out tagged ports on the switch. The VLANs can also be configured to
accept tagged packets in tagged ports, strip the tags off the packets, and send the packets back out other
untagged ports. This allows a network administrator to set up the switch so he can support devices on the
network that do not support VLAN Tagged packets. The administrator can also set up the ports to discard
any packets that are tagged or to discard any packets that are untagged based on a hybrid VLAN of both
tagged and untagged ports, and using the VLAN Ingress Filter on the switch.
The 9000 Series switch also has the ability to allow overlapping VLANs. Overlapping VLANs
gives the user the ability to have one or more ports share two or more VLAN groups. For more information
and examples on how this could be implemented please see our website’s technical documents.
Rapid Spanning Tree Protocol
The rapid spanning tree protocol as specified in IEEE 802.1D-2004 is supported. One Spanning Tree
per a unit is supported. Besides a Spanning Tree per VLAN is also supported.
The Rapid Spanning Tree Protocol (RSTP) supersedes the Spanning Tree Protocol (STP) which was
described in IEEE 802.1D-1998. The RSTP is used to configure a simply connected active network
topology from the arbitrarily connected bridges of a bridged network. Bridges effectively connect just the
LANs to which their forwarding ports are attached. Ports that are in a blocking state do not forward frames.
The bridges in the network exchange sufficient information to automatically derive a spanning tree.
RSTP allows for much quicker learning of network topology changes than the older STP. RSTP
supports new and improved features such as rapid transition to forwarding state. RSTP also sends out new
BPDUs every hello time instead of just relaying them. RSTP interoperates with older STP switches by
falling back to the older STP when the older BPDUs are detected on bridge ports. The user can also
manually configure bridge ports to use the older STP when desired.
SNMP Traps
The 9000 Series switch supports up to 5 SNMP Trap Stations to which SNMP Traps will be sent.
The switch supports three standard traps; Link Up, Link Down, and Cold Start. SNMP Traps will be sent to
all the stations configured on the switch if a port Link goes up or down, and when the switch first powers
up.