D-Link DGS-3000 Series Reference Manual page 106

The fields that can be configured are described below:
Parameter
From Port / To Port
External Cost (0=Auto)
P2P
Restricted TCN
Migrate
Port STP
Forward BPDU
Edge
DGS-3000 Series Gigabit Ethernet Switch Web UI Reference Guide
Figure 4-30 STP Port Settings window
Description
Select the starting and ending ports to be configured.
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). 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. The default
port cost for a 100Mbps port is 200000 and the default port cost for a Gigabit port is
20000. Enter 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.
Choosing the True parameter indicates a point-to-point (P2P) shared link. P2P ports are
similar to edge ports; however they are restricted in that a P2P port must operate in full
duplex. Like edge ports, P2P ports transition to a forwarding state rapidly thus benefiting
from RSTP. A P2P value of False indicates that the port cannot have P2P status. Auto
allows the port to have P2P status whenever possible and operate as if the P2P status
were True. If the port cannot maintain this status, (for example if the port is forced to
half-duplex operation) the P2P status changes to operate as if the P2P value were
False. The default setting for this parameter is Auto.
Topology Change Notification is a simple BPDU that a bridge sends out to its root port
to signal a topology change. Restricted TCN can be toggled between True and False. If
set to True, this stops the port from propagating received topology change notifications
and topology changes to other ports. The default is False.
When operating in RSTP mode, selecting Yes forces the port that has been selected to
transmit RSTP BPDUs.
This drop-down menu allows you to enable or disable STP for the selected group of
ports. The default is Enabled.
Use the drop-down menu to enable or disable the flooding of BPDU packets when STP
is disabled.
Choosing the True parameter designates the port as an edge port. Edge ports cannot
create loops, however an edge port can lose edge port status if a topology change
creates a potential for a loop. An edge port normally should not receive BPDU packets.
If a BPDU packet is received, it automatically loses edge port status. Choosing the
False parameter indicates that the port does not have edge port status. Alternatively,
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