DGS-3048 Gigabit Ethernet Switch Manual
67
In addition to setting Spanning Tree parameters for use on the switch level, the Switch allows for the configuration of
groups of ports, each port-group of which will have its own spanning tree, and will require some of its own configuration
settings. An STP Group will use the switch-level parameters entered above, with the addition of Port Priority and Port Cost.
An STP Group spanning tree works in the same way as the switch-level spanning tree, but the root bridge concept is
replaced with a root port concept. A root port is a port of the group that is elected based on port priority and port cost, to be
the connection to the network for the group. Redundant links will be blocked, just as redundant links are blocked on the
switch level.
The STP on the switch level blocks redundant links between switches (and similar network devices). The port level STP
will block redundant links within an STP Group.
It is advisable to define an STP Group to correspond to a VLAN group of ports.
The following fields can be set:
Parameter Description
From/To
A consecutive group of ports may be configured starting with the selected port.
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).
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.
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 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.
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
.
State
This drop-down menu allows you to enable or disable STP for the selected group of
ports. The default is
Disabled
.
Click
Apply
to implement changes made.
MST Configuration Identification
The following windows allow the user to configure a MSTI instance on the Switch. These settings will uniquely identify a
multiple spanning tree instance set on the Switch. The Switch initially possesses one
CIST
or Common Internal Spanning
Tree of which the user may modify the parameters for but cannot change the MSTI ID for, and cannot be deleted. To view
the
Current
MST Configuration Identification
window, click
Administration > Spanning Tree > MST Configuration
Identification
:
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