System information

xStack
®
DGS-3200 Series Layer 2 Gigabit Ethernet Managed Switch
83
Figure 3 - 35. STP Port Settings window
It is advisable to define an STP Group to correspond to a VLAN group of ports.
The following STP Port Settings fields can be set:
Parameter Description
From Port
The beginning port in a consecutive group of ports to be configured.
To Port
The ending port in a consecutive group of ports to be configured.
External Cost
(0=Auto)
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.
P2P
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.
Restricted TCN
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.
Migrate
When operating in RSTP mode, selecting Yes forces the port that has been selected to
transmit RSTP BPDUs.
State
This drop-down menu allows you to enable or disable STP for the selected group of ports.
The default is Enabled.
Forward BPDU
Use the pull-down menu to enable or disable the flooding of BPDU packets when STP is
disabled.
Edge
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 poten-
tial for a loop. An edge port normally should not receive BPDU packets. If a BPDU packet is