Virtual Lans; Nn47924-301 01.01 Standard 1.00 October - Nortel BES50GE-12T PWR User Manual

Spanning Tree Protocol loops
STA uses a distributed algorithm to select a bridging device (STA-compliant
switch, bridge, or router) that serves as the root of the spanning tree
network. It selects a root port on each bridging device (except for the root
device), which incurs the lowest path cost when forwarding a packet from
that device to the root device. Then it selects a designated bridging device
from each LAN, which incurs the lowest path cost when forwarding a packet
from that LAN to the root device. All ports connected to designated bridging
devices are assigned as designated ports. After determining the lowest cost
spanning tree, STA enables all root ports and designated ports and disables
all other ports. Network packets are therefore only forwarded between root
ports and designated ports, eliminating any possible network loops.
After a stable network topology is established, all bridges listen for Hello
Bridge Protocol Data Units (BPDUs) transmitted from the root bridge. If a
bridge does not receive a Hello BPDU after a predefined interval (Maximum
Age), the bridge assumes that the link to the root bridge is down. This
bridge then initiates negotiations with other bridges to reconfigure the
network to reestablish a valid network topology.

Virtual LANs

The switch supports up to 32 Virtual LANs (VLANs). A VLAN is a collection
of network nodes that share the same collision domain regardless of their
physical location or connection point in the network. The switch supports
tagged VLANs based on the IEEE 802.1Q standard. Members of VLAN
groups can be dynamically learned through GVRP, or ports can be manually
assigned to a specific set of VLANs. This allows the switch to restrict traffic
to the VLAN groups to which a user is assigned. By segmenting your
network into VLANs, you can:
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Copyright © 2006, Nortel Networks
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Eliminate broadcast storms, which severely degrade performance in
a flat network.
Simplify network management for node changes and moves by remotely
configuring VLAN membership for any port, rather than having to
manually change the network connection.
Using the Nortel Business Ethernet Switch 50 Series
NN47924-301 01.01 Standard
1.00 October 2006
SMB
Key software features 133
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