D-Link DES-6300, User Manual, Page: 34 / 298

Modular L3 Ethernet Switch User’s Guide
25
On The Port Level
Root Port – Each switch has a Root Port. This is the port that has the lowest Path Cost to the
Root Bridge. In case there are several such ports, then the one with the lowest Port Identifier is
the Root Port.
Designated Port – This is the port on each Designated Bridge that is attached to the LAN
segment for which the switch is the Designated Bridge.
Port Priority – The smaller this number, the higher the Port Priority is. With higher Port
Priority, the higher the probability that the port will be selected as the Root Port.
Path Cost – This is a changeable parameter and may be modified according to the STA
specification. The 1000Mbps segment has an assigned Path Cost of 4, the 100Mbps segment has
an assigned Path Cost of 19, and each 10Mbps segment has an assigned Path Cost of 100, based
on the STA specifications.
User-Changeable STA Parameters
The factory default setting should cover the majority of installations. However, it is advisable to
keep the default settings as set at the factory, unless it is absolutely necessary. The user
changeable parameters in the Switch are as follows:
Bridge Priority – A Bridge Priority can be from 0 to 65535. 0 is equal to the highest Bridge
Priority.
Bridge Hello Time – The Hello Time can be from 1 to 10 seconds. This is the interval between
two transmissions of BPDU packets sent by the Root Bridge to tell all other Switches that it is
indeed the Root Bridge. If you set a Hello Time for your Switch, and it is not the Root Bridge,
the set Hello Time will be used if and when your Switch becomes the Root Bridge.
Note : The Hello Time cannot be longer than the Max. Age. Otherwise, a configuration error
will occur.
Bridge Max. Age – The Max. Age can be from 6 to 40 seconds. At the end of the Max. Age, if a
BPDU has still not been received from the Root Bridge, your 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.
Bridge Forward Delay – The Forward Delay can be from 4 to 30 seconds. This is the time any
port on the Switch spends in the listening state while moving from the blocking state to the
forwarding state.
Observe the following formulas when you set the above parameters:
Max. Age
≤
2 x (Forward Delay - 1 second)
Max. Age
≥
2 x (Hello Time + 1 second)
Port Priority – A Port Priority can be from 0 to 255. The lower the number, the greater the
probability the port will be chosen as the Root Port.