Spanning Tree Protocol; Stp Operation Levels - D-Link DGS-3224TG User Manual

Each port on the switch is a unique collision domain and the switch filters (discards) packets whose
destination lies on the same port as where it originated. This keeps local packets from disrupting
communications on other parts of the network.
For intrusion control, whenever a switch encounters a packet originating from or destined to a MAC
address entered into the filter table, the switch will discard the packet.
Some filtering is done automatically by the switch:
•
Dynamic filtering – automatic learning and aging of MAC addresses and their location on the
network. Filtering occurs to keep local traffic confined to its segment.
•
Filtering done by the Spanning Tree Protocol that can filter packets based on topology,
making sure that signal loops don't occur.
•
Filtering done for VLAN integrity. Packets from a member of a VLAN (VLAN 2, for example)
destined for a device on another VLAN (VLAN 3) will be filtered.

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 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

STP calculates the Bridge Identifier for each switch and then sets the Root Bridge and the Designated
Bridges.
The following are the user-configurable STP parameters for the switch level:
Parameter Description
Bridge Identifier A combination of the User-set
priority and the switch's MAC
DGS-3224TG Gigabit Ethernet Switch User's Guide
Default
Value
32768 + MAC
16