User manual

xStack DGS/DXS-3300 Series Layer 3 Stackable Gigabit Ethernet Switch User Manual
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Figure 6- 30. STP Instance Operational Status – Previously Configured MSTI
The following parameters may be viewed in the STP Instance Operational Status windows:
Parameter Description
Designated Root
Bridge
This field will show the priority and MAC address of the Root Bridge.
External Root Cost
This 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).
• 0 (auto) - Setting 0 for the external cost will automatically set the speed for
forwarding packets to the specified port(s) in the list for optimal efficiency.
Default port cost: 100Mbps port = 200000. Gigabit port = 20000.
• value 1-200000000 - Define a value between 1 and 200000000 to determine
the external cost. The lower the number, the greater the probability the port
will be chosen to forward packets.
Regional Root Bridge
This field will show the priority and MAC address of the Regional (Internal) Root
Bridge. This MAC address should be the MAC address of the Switch.
Internal Root Cost
This parameter is set to represent the relative cost of forwarding packets to specified
ports when an interface is selected within a STP instance. The default setting is 0
(auto). There are two options:
• 0 (auto) - Selecting this parameter for the internalCost will set quickest route
automatically and optimally for an interface. The default value is derived
from the media speed of the interface.
• value 1-2000000 - Selecting this parameter with a value in the range of 1-
2000000 will set the quickest route when a loop occurs. A lower Internal
cost represents a quicker transmission.
Designated Bridge
This field will show the priority and MAC address of the Designated Bridge. The
information shown in this table comes from a BPDU packet originating from this
bridge.
Root Port
This is the port on the Switch that is physically connected to the Root Bridge.
Max Age
The Max Age 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 your switch has the lowest
Bridge Identifier, it will become the Root Bridge. The user may choose a time between
6 and 40 seconds. The default value is 20.