Filter
Top Products
DES-3226 NWay Standalone Fast Ethernet Switch User’s Guide
• MAC address filtering – the manual entry of specific MAC addresses to be filtered from the
network. Packets sent from one manually entered MAC address can be filtered from the
network. The entry may be specified as source, destination, or both.
Spanning Tree Protocol
The IEEE 802.1D Spanning Tree Protocol allows for the blocking of links between switches that form
loops within the network. When multiple links between switches are detected, a primary link is
established. Duplicated links are blocked from use and become standby links. The protocol allows for
the duplicate links to be used in the event of a failure of the primary link. Once the Spanning Tree
Protocol is configured and enabled, primary links are established and duplicated links are blocked
automatically. The reactivation of the blocked links (at the time of a primary link failure) is also
accomplished automatically – without operator intervention.
This automatic network reconfiguration provides maximum uptime to network users. However, the
concepts of the Spanning Tree Algorithm and protocol are a complicated and complex subject and must
be fully researched and understood. It is possible to cause serious degradation of the performance of
the network if the Spanning Tree is incorrectly configured. Please read the following before making any
changes from the default values.
The DES-3226 STP allows two levels of spanning trees to be configured. The first level constructs a
spanning tree on the links between switches. This is referred to as the Switch or Global level. The
second level is on a port basis. Ports are configured as individual members of a spanning tree and the
algorithm and protocol are applied to the specified ports. This is referred to as the Port or VLAN level.
The Switch STP performs the following functions:
• Creates a single spanning tree from any combination of switching or bridging elements.
• Automatically reconfigures the spanning tree to compensate for the failure, addition, or removal
of any element in the tree.
• Reconfigures the spanning tree without operator intervention.
STP Operation Levels
The Switch allows for two levels of operation: the switch level and the port level. The switch level forms
a spanning tree consisting of links between one or more switches. The port level constructs a spanning
tree consisting of groups of one or more ports. The STP operates in much the same way for both levels.
On the switch level, STP calculates the Bridge Identifier for each switch and then sets the Root Bridge
and the Designated Bridges.
On the port level, STP sets the Root Port and the Designated Ports.
The following are the user-configurable STP parameters for the switch level:
Parameter Description Default
Value
Bridge Identifier
(Not user-
configurable except
b
y
settin
g
p
riorit
y
A combination of the User-set
priority and the switch’s MAC
address. The Bridge Identifier
consists of two parts: a 16-bit
p
riorit
y
and a 48-bit Ethernet MAC
32768 + MAC
21