User manual

4 Configuration DES-1210 Metro Ethernet Managed Switch User Manual
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Maximum Age (6-40 sec): This value may be set to ensure that old information does not endlessly circulate
through redundant paths in the network, preventing the effective propagation of the new information. Set by
the Root Bridge, this value will aid in determining that the Switch has spanning tree configuration values
consistent with other devices on the bridged LAN. If the value ages out and a BPDU has still not been
received from the Root Bridge, the Switch will start sending its own BPDU to all other switches for permission
to become the Root Bridge. If it turns out that the Switch has the lowest Bridge Identifier, it will become the
Root Bridge. A time interval may be chosen between 6 and 40 seconds. The default value is 20. (Max Age
has to have a value bigger than Hello Time)
Hello Time (1-10 sec): The user may set the time interval between transmissions of configuration messages
by the root device, thus stating that the Switch is still functioning. The default is 2 seconds.
Forward Delay (4-30 sec): This sets the maximum amount of time that the root device will wait before
changing states. The default is 15 seconds.
Forwarding BPDU: Bridges use Bridge Protocol Data Units (BPDU) to provide spanning tree information.
STP BPDUs filtering is useful when a bridge interconnects two regions; each region needing a separate
spanning tree. BPDU filtering functions only when STP is disabled either globally or on a single interface.
Enabled - BPDU filtering is enabled on the port.
Disabled - BPDU forwarding is enabled on the port (if STP is disabled).
Root Bridge: Displays the MAC address of the Root Bridge.
Root Cost: Defines a metric that indicates the relative cost of forwarding packets to the specified port list.
Port cost can be set automatically or as a metric value. The default value is 0 (auto).
Root Maximum Age: Displays the Maximum Age of the Root Bridge. The default is 20.
Root Forward Delay: Displays the Forward Delay of the Root Bridge. The default is 15.
Root port: Displays the root port.
Click Apply for the settings to take effect. Click Refresh to renew the page.
Configuration > Spanning Tree > STP Port Settings
STP can be set up on a port per port basis. In addition to setting Spanning Tree parameters for use on the
switch level, the Switch allows for the configuration of the groups of ports, each port-group of which will have
its own spanning tree, and will require some of its own configuration settings.
An STP Group spanning tree works in the same way as the switch-level spanning tree, but the root bridge
concept is replaced with a root port concept. A root port is a port of the group that is elected based on port
priority and port cost, to be the connection to the network for the group. Redundant links will be blocked, just
as redundant links are blocked on the switch level.
The STP on the switch level blocks redundant links between switches (and similar network devices). The
port level STP will block redundant links within an STP Group.
It is advisable to define an STP Group to correspond to a VLAN group of ports.
Figure 4.83 – Configuration > Spanning Tree > STP Port Settings
From Port/To Port: A consecutive group of ports may be configured starting with the selected port.