Allied Telesis AT-9724TS Parameter Description Designated Root Bridge, External Root Cost

Figure 6- 32. 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
Regional Root Bridge	number, the greater the probability the port will be chosen to forward packets.
	This field will show the priority and MAC address of the Regional (Internal) Root Bridge.This MAC address
Internal Root Cost	should be the MAC address of the Switch.
	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
Designated Bridge	when a loop occurs.A lower Internal cost represents a quicker transmission.
	This field will show the priority and MAC address of the Designated Bridge.The information shown in this table
Root Port	comes from a BPDU packet originating from this bridge.
	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.
Forward Delay	The Forward Delay can be from 4 to 30 seconds.Any port on the Switch spends this time in the listening
Last Topology Change	state while moving from the blocking state to the forwarding state.
	This field shows the time, in seconds, since the last spanning tree topology change.
Topology Changes Count	This field displays the number of times that the spanning tree topology has changed since the original initial
	boot up of the Switch.

Allied Telesyn AT-9724TS High-Density Layer 3 Stackable Gigabit Ethernet Switch 50